Пример #1
0
std::unique_ptr<Message> LegacyReplyBuilder::done() {
    invariant(_state == State::kOutputDocs);

    BSONObj reply = uassertStatusOK(rpc::downconvertReplyMetadata(_commandReply, _metadata));

    BufBuilder bufBuilder;
    bufBuilder.skip(sizeof(QueryResult::Value));

    if (_allowAddingOutputDocs) {
        BSONObjBuilder topBuilder(bufBuilder);
        for (const auto& el : reply) {
            if (kCursorTag != el.fieldNameStringData()) {
                topBuilder.append(el);
                continue;
            }
            invariant(el.isABSONObj());
            BSONObjBuilder curBuilder(topBuilder.subobjStart(kCursorTag));
            for (const auto& insideEl : el.Obj()) {
                if (kFirstBatchTag != insideEl.fieldNameStringData()) {
                    curBuilder.append(insideEl);
                    continue;
                }
                invariant(insideEl.isABSONObj());
                BSONArrayBuilder arrBuilder(curBuilder.subarrayStart(kFirstBatchTag));
                for (const auto& doc : _outputDocs) {
                    arrBuilder.append(doc);
                }
                arrBuilder.doneFast();
            }
            curBuilder.doneFast();
        }
        topBuilder.doneFast();
    } else {
        reply.appendSelfToBufBuilder(bufBuilder);
    }

    auto msgHeaderSz = static_cast<std::size_t>(MsgData::MsgDataHeaderSize);

    invariant(static_cast<std::size_t>(bufBuilder.len()) + msgHeaderSz <=
              mongol::MaxMessageSizeBytes);

    QueryResult::View qr = bufBuilder.buf();

    qr.setResultFlagsToOk();
    qr.msgdata().setLen(bufBuilder.len());
    qr.msgdata().setOperation(opReply);
    qr.setCursorId(0);
    qr.setStartingFrom(0);
    qr.setNReturned(1);

    _message->setData(qr.view2ptr(), true);
    bufBuilder.decouple();

    _state = State::kDone;
    return std::move(_message);
}
Пример #2
0
void OpQueryReplyBuilder::putInMessage(
    Message* out, int queryResultFlags, int nReturned, int startingFrom, long long cursorId) {
    QueryResult::View qr = _buffer.buf();
    qr.setResultFlags(queryResultFlags);
    qr.msgdata().setLen(_buffer.len());
    qr.msgdata().setOperation(opReply);
    qr.setCursorId(cursorId);
    qr.setStartingFrom(startingFrom);
    qr.setNReturned(nReturned);
    out->setData(_buffer.release());  // transport will free
}
Пример #3
0
void generateLegacyQueryErrorResponse(const AssertionException* exception,
                                      const QueryMessage& queryMessage,
                                      CurOp* curop,
                                      Message* response) {
    curop->debug().exceptionInfo = exception->getInfo();

    log(LogComponent::kQuery) << "assertion " << exception->toString() << " ns:" << queryMessage.ns
                              << " query:" << (queryMessage.query.valid()
                                                   ? queryMessage.query.toString()
                                                   : "query object is corrupt");
    if (queryMessage.ntoskip || queryMessage.ntoreturn) {
        log(LogComponent::kQuery) << " ntoskip:" << queryMessage.ntoskip
                                  << " ntoreturn:" << queryMessage.ntoreturn;
    }

    const SendStaleConfigException* scex = (exception->getCode() == ErrorCodes::SendStaleConfig)
        ? static_cast<const SendStaleConfigException*>(exception)
        : NULL;

    BSONObjBuilder err;
    exception->getInfo().append(err);
    if (scex) {
        err.append("ok", 0.0);
        err.append("ns", scex->getns());
        scex->getVersionReceived().addToBSON(err, "vReceived");
        scex->getVersionWanted().addToBSON(err, "vWanted");
    }
    BSONObj errObj = err.done();

    if (scex) {
        log(LogComponent::kQuery) << "stale version detected during query over " << queryMessage.ns
                                  << " : " << errObj;
    }

    BufBuilder bb;
    bb.skip(sizeof(QueryResult::Value));
    bb.appendBuf((void*)errObj.objdata(), errObj.objsize());

    // TODO: call replyToQuery() from here instead of this!!! see dbmessage.h
    QueryResult::View msgdata = bb.buf();
    bb.decouple();
    QueryResult::View qr = msgdata;
    qr.setResultFlags(ResultFlag_ErrSet);
    if (scex)
        qr.setResultFlags(qr.getResultFlags() | ResultFlag_ShardConfigStale);
    qr.msgdata().setLen(bb.len());
    qr.msgdata().setOperation(opReply);
    qr.setCursorId(0);
    qr.setStartingFrom(0);
    qr.setNReturned(1);
    response->setData(msgdata.view2ptr(), true);
}
Пример #4
0
    void replyToQuery( int queryResultFlags, Message& response, const BSONObj& resultObj ) {
        BufBuilder bufBuilder;
        bufBuilder.skip( sizeof( QueryResult::Value ));
        bufBuilder.appendBuf( reinterpret_cast< void *>(
                const_cast< char* >( resultObj.objdata() )), resultObj.objsize() );

        QueryResult::View queryResult = bufBuilder.buf();
        bufBuilder.decouple();

        queryResult.setResultFlags(queryResultFlags);
        queryResult.msgdata().setLen(bufBuilder.len());
        queryResult.msgdata().setOperation( opReply );
        queryResult.setCursorId(0);
        queryResult.setStartingFrom(0);
        queryResult.setNReturned(1);

        response.setData( queryResult.view2ptr(), true ); // transport will free
    }
Пример #5
0
Message LegacyReplyBuilder::done() {
    invariant(_state == State::kOutputDocs);

    QueryResult::View qr = _builder.buf();

    qr.setResultFlagsToOk();
    qr.msgdata().setLen(_builder.len());
    qr.msgdata().setOperation(opReply);
    qr.setCursorId(0);
    qr.setStartingFrom(0);
    qr.setNReturned(1);

    _message.setData(qr.view2ptr(), true);
    _builder.decouple();

    _state = State::kDone;
    return std::move(_message);
}
Пример #6
0
 void replyToQuery(int queryResultFlags,
                   AbstractMessagingPort* p, Message& requestMsg,
                   void *data, int size,
                   int nReturned, int startingFrom,
                   long long cursorId 
                   ) {
     BufBuilder b(32768);
     b.skip(sizeof(QueryResult::Value));
     b.appendBuf(data, size);
     QueryResult::View qr = b.buf();
     qr.setResultFlags(queryResultFlags);
     qr.msgdata().setLen(b.len());
     qr.msgdata().setOperation(opReply);
     qr.setCursorId(cursorId);
     qr.setStartingFrom(startingFrom);
     qr.setNReturned(nReturned);
     b.decouple();
     Message resp(qr.view2ptr(), true);
     p->reply(requestMsg, resp, requestMsg.header().getId());
 }
Пример #7
0
Message LegacyReplyBuilder::done() {
    invariant(_haveCommandReply);

    QueryResult::View qr = _builder.buf();

    if (_staleConfigError) {
        // For compatibility with legacy mongos, we need to set this result flag on StaleConfig
        qr.setResultFlags(ResultFlag_ErrSet | ResultFlag_ShardConfigStale);
    } else {
        qr.setResultFlagsToOk();
    }

    qr.msgdata().setLen(_builder.len());
    qr.msgdata().setOperation(opReply);
    qr.setCursorId(0);
    qr.setStartingFrom(0);
    qr.setNReturned(1);

    _message.setData(_builder.release());

    return std::move(_message);
}
Пример #8
0
    std::string newRunQuery(OperationContext* txn,
                            Message& m,
                            QueryMessage& q,
                            CurOp& curop,
                            Message &result,
                            bool fromDBDirectClient) {
        // Validate the namespace.
        const char *ns = q.ns;
        uassert(16332, "can't have an empty ns", ns[0]);

        const NamespaceString nsString(ns);
        uassert(16256, str::stream() << "Invalid ns [" << ns << "]", nsString.isValid());

        // Set curop information.
        curop.debug().ns = ns;
        curop.debug().ntoreturn = q.ntoreturn;
        curop.debug().query = q.query;
        curop.setQuery(q.query);

        // If the query is really a command, run it.
        if (nsString.isCommand()) {
            int nToReturn = q.ntoreturn;
            uassert(16979, str::stream() << "bad numberToReturn (" << nToReturn
                                         << ") for $cmd type ns - can only be 1 or -1",
                    nToReturn == 1 || nToReturn == -1);

            curop.markCommand();

            BufBuilder bb;
            bb.skip(sizeof(QueryResult::Value));

            BSONObjBuilder cmdResBuf;
            if (!runCommands(txn, ns, q.query, curop, bb, cmdResBuf, false, q.queryOptions)) {
                uasserted(13530, "bad or malformed command request?");
            }

            curop.debug().iscommand = true;
            // TODO: Does this get overwritten/do we really need to set this twice?
            curop.debug().query = q.query;

            QueryResult::View qr = bb.buf();
            bb.decouple();
            qr.setResultFlagsToOk();
            qr.msgdata().setLen(bb.len());
            curop.debug().responseLength = bb.len();
            qr.msgdata().setOperation(opReply);
            qr.setCursorId(0);
            qr.setStartingFrom(0);
            qr.setNReturned(1);
            result.setData(qr.view2ptr(), true);
            return "";
        }

        const NamespaceString nss(q.ns);

        // Parse the qm into a CanonicalQuery.
        CanonicalQuery* cq;
        Status canonStatus = CanonicalQuery::canonicalize(
                                    q, &cq, WhereCallbackReal(txn, StringData(nss.db())));
        if (!canonStatus.isOK()) {
            uasserted(17287, str::stream() << "Can't canonicalize query: " << canonStatus.toString());
        }

        QLOG() << "Running query:\n" << cq->toString();
        LOG(2) << "Running query: " << cq->toStringShort();

        // Parse, canonicalize, plan, transcribe, and get a plan executor.
        PlanExecutor* rawExec = NULL;

        // We use this a lot below.
        const LiteParsedQuery& pq = cq->getParsed();

        AutoGetCollectionForRead ctx(txn, nss);

        const int dbProfilingLevel = (ctx.getDb() != NULL) ? ctx.getDb()->getProfilingLevel() :
                                                             serverGlobalParams.defaultProfile;

        Collection* collection = ctx.getCollection();

        // We'll now try to get the query executor that will execute this query for us. There
        // are a few cases in which we know upfront which executor we should get and, therefore,
        // we shortcut the selection process here.
        //
        // (a) If the query is over a collection that doesn't exist, we use an EOFStage.
        //
        // (b) if the query is a replication's initial sync one, we use a specifically designed
        // stage that skips extents faster (see details in exec/oplogstart.h).
        //
        // Otherwise we go through the selection of which executor is most suited to the
        // query + run-time context at hand.
        Status status = Status::OK();
        if (NULL != collection && pq.getOptions().oplogReplay) {
            // Takes ownership of 'cq'.
            status = getOplogStartHack(txn, collection, cq, &rawExec);
        }
        else {
            size_t options = QueryPlannerParams::DEFAULT;
            if (shardingState.needCollectionMetadata(pq.ns())) {
                options |= QueryPlannerParams::INCLUDE_SHARD_FILTER;
            }
            // Takes ownership of 'cq'.
            status = getExecutor(txn, collection, cq, PlanExecutor::YIELD_AUTO, &rawExec, options);
        }

        if (!status.isOK()) {
            // NOTE: Do not access cq as getExecutor has deleted it.
            uasserted(17007, "Unable to execute query: " + status.reason());
        }

        verify(NULL != rawExec);
        auto_ptr<PlanExecutor> exec(rawExec);

        // If it's actually an explain, do the explain and return rather than falling through
        // to the normal query execution loop.
        if (pq.isExplain()) {
            BufBuilder bb;
            bb.skip(sizeof(QueryResult::Value));

            BSONObjBuilder explainBob;
            Explain::explainStages(exec.get(), ExplainCommon::EXEC_ALL_PLANS, &explainBob);

            // Add the resulting object to the return buffer.
            BSONObj explainObj = explainBob.obj();
            bb.appendBuf((void*)explainObj.objdata(), explainObj.objsize());

            curop.debug().iscommand = true;
            // TODO: Does this get overwritten/do we really need to set this twice?
            curop.debug().query = q.query;

            // Set query result fields.
            QueryResult::View qr = bb.buf();
            bb.decouple();
            qr.setResultFlagsToOk();
            qr.msgdata().setLen(bb.len());
            curop.debug().responseLength = bb.len();
            qr.msgdata().setOperation(opReply);
            qr.setCursorId(0);
            qr.setStartingFrom(0);
            qr.setNReturned(1);
            result.setData(qr.view2ptr(), true);
            return "";
        }

        // We freak out later if this changes before we're done with the query.
        const ChunkVersion shardingVersionAtStart = shardingState.getVersion(cq->ns());

        // Handle query option $maxTimeMS (not used with commands).
        curop.setMaxTimeMicros(static_cast<unsigned long long>(pq.getMaxTimeMS()) * 1000);
        txn->checkForInterrupt(); // May trigger maxTimeAlwaysTimeOut fail point.

        // uassert if we are not on a primary, and not a secondary with SlaveOk query parameter set.
        bool slaveOK = pq.getOptions().slaveOk || pq.hasReadPref();
        status = repl::getGlobalReplicationCoordinator()->checkCanServeReadsFor(
                txn,
                NamespaceString(cq->ns()),
                slaveOK);
        uassertStatusOK(status);

        // If this exists, the collection is sharded.
        // If it doesn't exist, we can assume we're not sharded.
        // If we're sharded, we might encounter data that is not consistent with our sharding state.
        // We must ignore this data.
        CollectionMetadataPtr collMetadata;
        if (!shardingState.needCollectionMetadata(pq.ns())) {
            collMetadata = CollectionMetadataPtr();
        }
        else {
            collMetadata = shardingState.getCollectionMetadata(pq.ns());
        }

        // Run the query.
        // bb is used to hold query results
        // this buffer should contain either requested documents per query or
        // explain information, but not both
        BufBuilder bb(32768);
        bb.skip(sizeof(QueryResult::Value));

        // How many results have we obtained from the executor?
        int numResults = 0;

        // If we're replaying the oplog, we save the last time that we read.
        OpTime slaveReadTill;

        // Do we save the PlanExecutor in a ClientCursor for getMore calls later?
        bool saveClientCursor = false;

        BSONObj obj;
        PlanExecutor::ExecState state;
        // uint64_t numMisplacedDocs = 0;

        // Get summary info about which plan the executor is using.
        curop.debug().planSummary = Explain::getPlanSummary(exec.get());

        while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
            // Add result to output buffer.
            bb.appendBuf((void*)obj.objdata(), obj.objsize());

            // Count the result.
            ++numResults;

            // Possibly note slave's position in the oplog.
            if (pq.getOptions().oplogReplay) {
                BSONElement e = obj["ts"];
                if (Date == e.type() || Timestamp == e.type()) {
                    slaveReadTill = e._opTime();
                }
            }

            // TODO: only one type of 2d search doesn't support this.  We need a way to pull it out
            // of CanonicalQuery. :(
            const bool supportsGetMore = true;
            if (!supportsGetMore && (enough(pq, numResults)
                                     || bb.len() >= MaxBytesToReturnToClientAtOnce)) {
                break;
            }
            else if (enoughForFirstBatch(pq, numResults, bb.len())) {
                QLOG() << "Enough for first batch, wantMore=" << pq.wantMore()
                       << " numToReturn=" << pq.getNumToReturn()
                       << " numResults=" << numResults
                       << endl;
                // If only one result requested assume it's a findOne() and don't save the cursor.
                if (pq.wantMore() && 1 != pq.getNumToReturn()) {
                    QLOG() << " executor EOF=" << exec->isEOF() << endl;
                    saveClientCursor = !exec->isEOF();
                }
                break;
            }
        }

        // If we cache the executor later, we want to deregister it as it receives notifications
        // anyway by virtue of being cached.
        //
        // If we don't cache the executor later, we are deleting it, so it must be deregistered.
        //
        // So, no matter what, deregister the executor.
        exec->deregisterExec();

        // Caller expects exceptions thrown in certain cases.
        if (PlanExecutor::EXEC_ERROR == state) {
            scoped_ptr<PlanStageStats> stats(exec->getStats());
            error() << "Plan executor error, stats: "
                    << Explain::statsToBSON(*stats);
            uasserted(17144, "Executor error: " + WorkingSetCommon::toStatusString(obj));
        }

        // Why save a dead executor?
        if (PlanExecutor::DEAD == state) {
            saveClientCursor = false;
        }
        else if (pq.getOptions().tailable) {
            // If we're tailing a capped collection, we don't bother saving the cursor if the
            // collection is empty. Otherwise, the semantics of the tailable cursor is that the
            // client will keep trying to read from it. So we'll keep it around.
            if (collection && collection->numRecords(txn) != 0 && pq.getNumToReturn() != 1) {
                saveClientCursor = true;
            }
        }

        // TODO(greg): This will go away soon.
        if (!shardingState.getVersion(pq.ns()).isWriteCompatibleWith(shardingVersionAtStart)) {
            // if the version changed during the query we might be missing some data and its safe to
            // send this as mongos can resend at this point
            throw SendStaleConfigException(pq.ns(), "version changed during initial query",
                                           shardingVersionAtStart,
                                           shardingState.getVersion(pq.ns()));
        }

        const logger::LogComponent queryLogComponent = logger::LogComponent::kQuery;
        const logger::LogSeverity logLevelOne = logger::LogSeverity::Debug(1);

        PlanSummaryStats summaryStats;
        Explain::getSummaryStats(exec.get(), &summaryStats);

        curop.debug().ntoskip = pq.getSkip();
        curop.debug().nreturned = numResults;
        curop.debug().scanAndOrder = summaryStats.hasSortStage;
        curop.debug().nscanned = summaryStats.totalKeysExamined;
        curop.debug().nscannedObjects = summaryStats.totalDocsExamined;
        curop.debug().idhack = summaryStats.isIdhack;

        // Set debug information for consumption by the profiler.
        if (dbProfilingLevel > 0 ||
            curop.elapsedMillis() > serverGlobalParams.slowMS ||
            logger::globalLogDomain()->shouldLog(queryLogComponent, logLevelOne)) {
            // Get BSON stats.
            scoped_ptr<PlanStageStats> execStats(exec->getStats());
            BSONObjBuilder statsBob;
            Explain::statsToBSON(*execStats, &statsBob);
            curop.debug().execStats.set(statsBob.obj());

            // Replace exec stats with plan summary if stats cannot fit into CachedBSONObj.
            if (curop.debug().execStats.tooBig() && !curop.debug().planSummary.empty()) {
                BSONObjBuilder bob;
                bob.append("summary", curop.debug().planSummary.toString());
                curop.debug().execStats.set(bob.done());
            }
        }

        long long ccId = 0;
        if (saveClientCursor) {
            // We won't use the executor until it's getMore'd.
            exec->saveState();

            // Allocate a new ClientCursor.  We don't have to worry about leaking it as it's
            // inserted into a global map by its ctor.
            ClientCursor* cc = new ClientCursor(collection, exec.get(),
                                                cq->getParsed().getOptions().toInt(),
                                                cq->getParsed().getFilter());
            ccId = cc->cursorid();

            if (fromDBDirectClient) {
                cc->setUnownedRecoveryUnit(txn->recoveryUnit());
            }
            else if (state == PlanExecutor::IS_EOF && pq.getOptions().tailable) {
                // Don't stash the RU for tailable cursors at EOF, let them get a new RU on their
                // next getMore.
            }
            else {
                // We stash away the RecoveryUnit in the ClientCursor.  It's used for subsequent
                // getMore requests.  The calling OpCtx gets a fresh RecoveryUnit.
                cc->setOwnedRecoveryUnit(txn->releaseRecoveryUnit());
                StorageEngine* storageEngine = getGlobalEnvironment()->getGlobalStorageEngine();
                txn->setRecoveryUnit(storageEngine->newRecoveryUnit(txn));
            }

            QLOG() << "caching executor with cursorid " << ccId
                   << " after returning " << numResults << " results" << endl;

            // ClientCursor takes ownership of executor.  Release to make sure it's not deleted.
            exec.release();

            // TODO document
            if (pq.getOptions().oplogReplay && !slaveReadTill.isNull()) {
                cc->slaveReadTill(slaveReadTill);
            }

            // TODO document
            if (pq.getOptions().exhaust) {
                curop.debug().exhaust = true;
            }

            // Set attributes for getMore.
            cc->setCollMetadata(collMetadata);
            cc->setPos(numResults);

            // If the query had a time limit, remaining time is "rolled over" to the cursor (for
            // use by future getmore ops).
            cc->setLeftoverMaxTimeMicros(curop.getRemainingMaxTimeMicros());
        }
        else {
            QLOG() << "Not caching executor but returning " << numResults << " results.\n";
        }

        // Add the results from the query into the output buffer.
        result.appendData(bb.buf(), bb.len());
        bb.decouple();

        // Fill out the output buffer's header.
        QueryResult::View qr = result.header().view2ptr();
        qr.setCursorId(ccId);
        curop.debug().cursorid = (0 == ccId ? -1 : ccId);
        qr.setResultFlagsToOk();
        qr.msgdata().setOperation(opReply);
        qr.setStartingFrom(0);
        qr.setNReturned(numResults);

        // curop.debug().exhaust is set above.
        return curop.debug().exhaust ? pq.ns() : "";
    }
Пример #9
0
    /**
     * Called by db/instance.cpp.  This is the getMore entry point.
     *
     * pass - when QueryOption_AwaitData is in use, the caller will make repeated calls 
     *        when this method returns an empty result, incrementing pass on each call.  
     *        Thus, pass == 0 indicates this is the first "attempt" before any 'awaiting'.
     */
    QueryResult::View newGetMore(OperationContext* txn,
                            const char* ns,
                            int ntoreturn,
                            long long cursorid,
                            CurOp& curop,
                            int pass,
                            bool& exhaust,
                            bool* isCursorAuthorized,
                            bool fromDBDirectClient) {

        // For testing, we may want to fail if we receive a getmore.
        if (MONGO_FAIL_POINT(failReceivedGetmore)) {
            invariant(0);
        }

        exhaust = false;

        // This is a read lock.
        const NamespaceString nss(ns);
        scoped_ptr<AutoGetCollectionForRead> ctx(new AutoGetCollectionForRead(txn, nss));
        Collection* collection = ctx->getCollection();
        uassert( 17356, "collection dropped between getMore calls", collection );

        QLOG() << "Running getMore, cursorid: " << cursorid << endl;

        // This checks to make sure the operation is allowed on a replicated node.  Since we are not
        // passing in a query object (necessary to check SlaveOK query option), the only state where
        // reads are allowed is PRIMARY (or master in master/slave).  This function uasserts if
        // reads are not okay.
        Status status = repl::getGlobalReplicationCoordinator()->checkCanServeReadsFor(
                txn,
                nss,
                true);
        uassertStatusOK(status);

        // A pin performs a CC lookup and if there is a CC, increments the CC's pin value so it
        // doesn't time out.  Also informs ClientCursor that there is somebody actively holding the
        // CC, so don't delete it.
        ClientCursorPin ccPin(collection, cursorid);
        ClientCursor* cc = ccPin.c();

        // If we're not being called from DBDirectClient we want to associate the RecoveryUnit
        // used to create the execution machinery inside the cursor with our OperationContext.
        // If we throw or otherwise exit this method in a disorderly fashion, we must ensure
        // that further calls to getMore won't fail, and that the provided OperationContext
        // has a valid RecoveryUnit.  As such, we use RAII to accomplish this.
        //
        // This must be destroyed before the ClientCursor is destroyed.
        std::auto_ptr<ScopedRecoveryUnitSwapper> ruSwapper;

        // These are set in the QueryResult msg we return.
        int resultFlags = ResultFlag_AwaitCapable;

        int numResults = 0;
        int startingResult = 0;

        const int InitialBufSize =
            512 + sizeof(QueryResult::Value) + MaxBytesToReturnToClientAtOnce;

        BufBuilder bb(InitialBufSize);
        bb.skip(sizeof(QueryResult::Value));

        if (NULL == cc) {
            cursorid = 0;
            resultFlags = ResultFlag_CursorNotFound;
        }
        else {
            // Quote: check for spoofing of the ns such that it does not match the one originally
            // there for the cursor
            uassert(17011, "auth error", str::equals(ns, cc->ns().c_str()));
            *isCursorAuthorized = true;

            // Restore the RecoveryUnit if we need to.
            if (fromDBDirectClient) {
                if (cc->hasRecoveryUnit())
                    invariant(txn->recoveryUnit() == cc->getUnownedRecoveryUnit());
            }
            else {
                if (!cc->hasRecoveryUnit()) {
                    // Start using a new RecoveryUnit
                    cc->setOwnedRecoveryUnit(
                        getGlobalEnvironment()->getGlobalStorageEngine()->newRecoveryUnit(txn));

                }
                // Swap RecoveryUnit(s) between the ClientCursor and OperationContext.
                ruSwapper.reset(new ScopedRecoveryUnitSwapper(cc, txn));
            }

            // Reset timeout timer on the cursor since the cursor is still in use.
            cc->setIdleTime(0);

            // TODO: fail point?

            // If the operation that spawned this cursor had a time limit set, apply leftover
            // time to this getmore.
            curop.setMaxTimeMicros(cc->getLeftoverMaxTimeMicros());
            txn->checkForInterrupt(); // May trigger maxTimeAlwaysTimeOut fail point.

            if (0 == pass) { 
                cc->updateSlaveLocation(txn, curop); 
            }

            if (cc->isAggCursor) {
                // Agg cursors handle their own locking internally.
                ctx.reset(); // unlocks
            }

            CollectionMetadataPtr collMetadata = cc->getCollMetadata();

            // If we're replaying the oplog, we save the last time that we read.
            OpTime slaveReadTill;

            // What number result are we starting at?  Used to fill out the reply.
            startingResult = cc->pos();

            // What gives us results.
            PlanExecutor* exec = cc->getExecutor();
            const int queryOptions = cc->queryOptions();

            // Get results out of the executor.
            exec->restoreState(txn);

            BSONObj obj;
            PlanExecutor::ExecState state;
            while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
                // Add result to output buffer.
                bb.appendBuf((void*)obj.objdata(), obj.objsize());

                // Count the result.
                ++numResults;

                // Possibly note slave's position in the oplog.
                if (queryOptions & QueryOption_OplogReplay) {
                    BSONElement e = obj["ts"];
                    if (Date == e.type() || Timestamp == e.type()) {
                        slaveReadTill = e._opTime();
                    }
                }

                if ((ntoreturn && numResults >= ntoreturn)
                    || bb.len() > MaxBytesToReturnToClientAtOnce) {
                    break;
                }
            }

            // We save the client cursor when there might be more results, and hence we may receive
            // another getmore. If we receive a EOF or an error, or 'exec' is dead, then we know
            // that we will not be producing more results. We indicate that the cursor is closed by
            // sending a cursorId of 0 back to the client.
            //
            // On the other hand, if we retrieve all results necessary for this batch, then
            // 'saveClientCursor' is true and we send a valid cursorId back to the client. In
            // this case, there may or may not actually be more results (for example, the next call
            // to getNext(...) might just return EOF).
            bool saveClientCursor = false;

            if (PlanExecutor::DEAD == state || PlanExecutor::EXEC_ERROR == state) {
                // Propagate this error to caller.
                if (PlanExecutor::EXEC_ERROR == state) {
                    scoped_ptr<PlanStageStats> stats(exec->getStats());
                    error() << "Plan executor error, stats: "
                            << Explain::statsToBSON(*stats);
                    uasserted(17406, "getMore executor error: " +
                              WorkingSetCommon::toStatusString(obj));
                }

                // If we're dead there's no way to get more results.
                saveClientCursor = false;

                // In the old system tailable capped cursors would be killed off at the
                // cursorid level.  If a tailable capped cursor is nuked the cursorid
                // would vanish.
                //
                // In the new system they die and are cleaned up later (or time out).
                // So this is where we get to remove the cursorid.
                if (0 == numResults) {
                    resultFlags = ResultFlag_CursorNotFound;
                }
            }
            else if (PlanExecutor::IS_EOF == state) {
                // EOF is also end of the line unless it's tailable.
                saveClientCursor = queryOptions & QueryOption_CursorTailable;
            }
            else {
                verify(PlanExecutor::ADVANCED == state);
                saveClientCursor = true;
            }

            if (!saveClientCursor) {
                ruSwapper.reset();
                ccPin.deleteUnderlying();
                // cc is now invalid, as is the executor
                cursorid = 0;
                cc = NULL;
                QLOG() << "getMore NOT saving client cursor, ended with state "
                       << PlanExecutor::statestr(state)
                       << endl;
            }
            else {
                // Continue caching the ClientCursor.
                cc->incPos(numResults);
                exec->saveState();
                QLOG() << "getMore saving client cursor ended with state "
                       << PlanExecutor::statestr(state)
                       << endl;

                if (PlanExecutor::IS_EOF == state && (queryOptions & QueryOption_CursorTailable)) {
                    if (!fromDBDirectClient) {
                        // Don't stash the RU. Get a new one on the next getMore.
                        ruSwapper.reset();
                        delete cc->releaseOwnedRecoveryUnit();
                    }

                    if ((queryOptions & QueryOption_AwaitData)
                            && (numResults == 0)
                            && (pass < 1000)) {
                        // Bubble up to the AwaitData handling code in receivedGetMore which will
                        // try again.
                        return NULL;
                    }
                }

                // Possibly note slave's position in the oplog.
                if ((queryOptions & QueryOption_OplogReplay) && !slaveReadTill.isNull()) {
                    cc->slaveReadTill(slaveReadTill);
                }

                exhaust = (queryOptions & QueryOption_Exhaust);

                // If the getmore had a time limit, remaining time is "rolled over" back to the
                // cursor (for use by future getmore ops).
                cc->setLeftoverMaxTimeMicros( curop.getRemainingMaxTimeMicros() );
            }
        }

        QueryResult::View qr = bb.buf();
        qr.msgdata().setLen(bb.len());
        qr.msgdata().setOperation(opReply);
        qr.setResultFlags(resultFlags);
        qr.setCursorId(cursorid);
        qr.setStartingFrom(startingResult);
        qr.setNReturned(numResults);
        bb.decouple();
        QLOG() << "getMore returned " << numResults << " results\n";
        return qr;
    }
Пример #10
0
    std::string runQuery(OperationContext* txn,
                         QueryMessage& q,
                         const NamespaceString& nss,
                         CurOp& curop,
                         Message &result) {
        // Validate the namespace.
        uassert(16256, str::stream() << "Invalid ns [" << nss.ns() << "]", nss.isValid());
        invariant(!nss.isCommand());

        // Set curop information.
        beginQueryOp(nss, q.query, q.ntoreturn, q.ntoskip, &curop);

        // Parse the qm into a CanonicalQuery.
        std::auto_ptr<CanonicalQuery> cq;
        {
            CanonicalQuery* cqRaw;
            Status canonStatus = CanonicalQuery::canonicalize(q,
                                                              &cqRaw,
                                                              WhereCallbackReal(txn, nss.db()));
            if (!canonStatus.isOK()) {
                uasserted(17287, str::stream() << "Can't canonicalize query: "
                                               << canonStatus.toString());
            }
            cq.reset(cqRaw);
        }
        invariant(cq.get());

        LOG(5) << "Running query:\n" << cq->toString();
        LOG(2) << "Running query: " << cq->toStringShort();

        // Parse, canonicalize, plan, transcribe, and get a plan executor.
        AutoGetCollectionForRead ctx(txn, nss);
        Collection* collection = ctx.getCollection();

        const int dbProfilingLevel = ctx.getDb() ? ctx.getDb()->getProfilingLevel() :
                                                   serverGlobalParams.defaultProfile;

        // We have a parsed query. Time to get the execution plan for it.
        std::unique_ptr<PlanExecutor> exec;
        {
            PlanExecutor* rawExec;
            Status execStatus = getExecutorFind(txn,
                                                collection,
                                                nss,
                                                cq.release(),
                                                PlanExecutor::YIELD_AUTO,
                                                &rawExec);
            uassertStatusOK(execStatus);
            exec.reset(rawExec);
        }
        const LiteParsedQuery& pq = exec->getCanonicalQuery()->getParsed();

        // If it's actually an explain, do the explain and return rather than falling through
        // to the normal query execution loop.
        if (pq.isExplain()) {
            BufBuilder bb;
            bb.skip(sizeof(QueryResult::Value));

            BSONObjBuilder explainBob;
            Explain::explainStages(exec.get(), ExplainCommon::EXEC_ALL_PLANS, &explainBob);

            // Add the resulting object to the return buffer.
            BSONObj explainObj = explainBob.obj();
            bb.appendBuf((void*)explainObj.objdata(), explainObj.objsize());

            // TODO: Does this get overwritten/do we really need to set this twice?
            curop.debug().query = q.query;

            // Set query result fields.
            QueryResult::View qr = bb.buf();
            bb.decouple();
            qr.setResultFlagsToOk();
            qr.msgdata().setLen(bb.len());
            curop.debug().responseLength = bb.len();
            qr.msgdata().setOperation(opReply);
            qr.setCursorId(0);
            qr.setStartingFrom(0);
            qr.setNReturned(1);
            result.setData(qr.view2ptr(), true);
            return "";
        }

        // We freak out later if this changes before we're done with the query.
        const ChunkVersion shardingVersionAtStart = shardingState.getVersion(nss.ns());

        // Handle query option $maxTimeMS (not used with commands).
        curop.setMaxTimeMicros(static_cast<unsigned long long>(pq.getMaxTimeMS()) * 1000);
        txn->checkForInterrupt(); // May trigger maxTimeAlwaysTimeOut fail point.

        // uassert if we are not on a primary, and not a secondary with SlaveOk query parameter set.
        bool slaveOK = pq.isSlaveOk() || pq.hasReadPref();
        Status serveReadsStatus = repl::getGlobalReplicationCoordinator()->checkCanServeReadsFor(
                txn,
                nss,
                slaveOK);
        uassertStatusOK(serveReadsStatus);

        // Run the query.
        // bb is used to hold query results
        // this buffer should contain either requested documents per query or
        // explain information, but not both
        BufBuilder bb(32768);
        bb.skip(sizeof(QueryResult::Value));

        // How many results have we obtained from the executor?
        int numResults = 0;

        // If we're replaying the oplog, we save the last time that we read.
        Timestamp slaveReadTill;

        BSONObj obj;
        PlanExecutor::ExecState state;
        // uint64_t numMisplacedDocs = 0;

        // Get summary info about which plan the executor is using.
        curop.debug().planSummary = Explain::getPlanSummary(exec.get());

        while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
            // Add result to output buffer.
            bb.appendBuf((void*)obj.objdata(), obj.objsize());

            // Count the result.
            ++numResults;

            // Possibly note slave's position in the oplog.
            if (pq.isOplogReplay()) {
                BSONElement e = obj["ts"];
                if (Date == e.type() || bsonTimestamp == e.type()) {
                    slaveReadTill = e.timestamp();
                }
            }

            if (enoughForFirstBatch(pq, numResults, bb.len())) {
                LOG(5) << "Enough for first batch, wantMore=" << pq.wantMore()
                       << " numToReturn=" << pq.getNumToReturn()
                       << " numResults=" << numResults
                       << endl;
                break;
            }
        }

        // If we cache the executor later, we want to deregister it as it receives notifications
        // anyway by virtue of being cached.
        //
        // If we don't cache the executor later, we are deleting it, so it must be deregistered.
        //
        // So, no matter what, deregister the executor.
        exec->deregisterExec();

        // Caller expects exceptions thrown in certain cases.
        if (PlanExecutor::FAILURE == state) {
            scoped_ptr<PlanStageStats> stats(exec->getStats());
            error() << "Plan executor error, stats: "
                    << Explain::statsToBSON(*stats);
            uasserted(17144, "Executor error: " + WorkingSetCommon::toStatusString(obj));
        }

        // TODO: Currently, chunk ranges are kept around until all ClientCursors created while the
        // chunk belonged on this node are gone. Separating chunk lifetime management from
        // ClientCursor should allow this check to go away.
        if (!shardingState.getVersion(nss.ns()).isWriteCompatibleWith(shardingVersionAtStart)) {
            // if the version changed during the query we might be missing some data and its safe to
            // send this as mongos can resend at this point
            throw SendStaleConfigException(nss.ns(), "version changed during initial query",
                                           shardingVersionAtStart,
                                           shardingState.getVersion(nss.ns()));
        }

        // Fill out curop based on query results. If we have a cursorid, we will fill out curop with
        // this cursorid later.
        long long ccId = 0;

        if (shouldSaveCursor(txn, collection, state, exec.get())) {
            // We won't use the executor until it's getMore'd.
            exec->saveState();

            // Allocate a new ClientCursor.  We don't have to worry about leaking it as it's
            // inserted into a global map by its ctor.
            ClientCursor* cc = new ClientCursor(collection->getCursorManager(),
                                                exec.release(),
                                                nss.ns(),
                                                pq.getOptions(),
                                                pq.getFilter());
            ccId = cc->cursorid();

            if (txn->getClient()->isInDirectClient()) {
                cc->setUnownedRecoveryUnit(txn->recoveryUnit());
            }
            else if (state == PlanExecutor::IS_EOF && pq.isTailable()) {
                // Don't stash the RU for tailable cursors at EOF, let them get a new RU on their
                // next getMore.
            }
            else {
                // We stash away the RecoveryUnit in the ClientCursor.  It's used for subsequent
                // getMore requests.  The calling OpCtx gets a fresh RecoveryUnit.
                txn->recoveryUnit()->abandonSnapshot();
                cc->setOwnedRecoveryUnit(txn->releaseRecoveryUnit());
                StorageEngine* storageEngine = getGlobalServiceContext()->getGlobalStorageEngine();
                invariant(txn->setRecoveryUnit(storageEngine->newRecoveryUnit(),
                                               OperationContext::kNotInUnitOfWork)
                          == OperationContext::kNotInUnitOfWork);
            }

            LOG(5) << "caching executor with cursorid " << ccId
                   << " after returning " << numResults << " results" << endl;

            // TODO document
            if (pq.isOplogReplay() && !slaveReadTill.isNull()) {
                cc->slaveReadTill(slaveReadTill);
            }

            // TODO document
            if (pq.isExhaust()) {
                curop.debug().exhaust = true;
            }

            cc->setPos(numResults);

            // If the query had a time limit, remaining time is "rolled over" to the cursor (for
            // use by future getmore ops).
            cc->setLeftoverMaxTimeMicros(curop.getRemainingMaxTimeMicros());

            endQueryOp(cc->getExecutor(), dbProfilingLevel, numResults, ccId, &curop);
        }
        else {
            LOG(5) << "Not caching executor but returning " << numResults << " results.\n";
            endQueryOp(exec.get(), dbProfilingLevel, numResults, ccId, &curop);
        }

        // Add the results from the query into the output buffer.
        result.appendData(bb.buf(), bb.len());
        bb.decouple();

        // Fill out the output buffer's header.
        QueryResult::View qr = result.header().view2ptr();
        qr.setCursorId(ccId);
        qr.setResultFlagsToOk();
        qr.msgdata().setOperation(opReply);
        qr.setStartingFrom(0);
        qr.setNReturned(numResults);

        // curop.debug().exhaust is set above.
        return curop.debug().exhaust ? nss.ns() : "";
    }
Пример #11
0
    /**
     * Called by db/instance.cpp.  This is the getMore entry point.
     *
     * pass - when QueryOption_AwaitData is in use, the caller will make repeated calls 
     *        when this method returns an empty result, incrementing pass on each call.  
     *        Thus, pass == 0 indicates this is the first "attempt" before any 'awaiting'.
     */
    QueryResult::View getMore(OperationContext* txn,
                              const char* ns,
                              int ntoreturn,
                              long long cursorid,
                              CurOp& curop,
                              int pass,
                              bool& exhaust,
                              bool* isCursorAuthorized) {

        // For testing, we may want to fail if we receive a getmore.
        if (MONGO_FAIL_POINT(failReceivedGetmore)) {
            invariant(0);
        }

        exhaust = false;

        const NamespaceString nss(ns);

        // Depending on the type of cursor being operated on, we hold locks for the whole getMore,
        // or none of the getMore, or part of the getMore.  The three cases in detail:
        //
        // 1) Normal cursor: we lock with "ctx" and hold it for the whole getMore.
        // 2) Cursor owned by global cursor manager: we don't lock anything.  These cursors don't
        //    own any collection state.
        // 3) Agg cursor: we lock with "ctx", then release, then relock with "unpinDBLock" and
        //    "unpinCollLock".  This is because agg cursors handle locking internally (hence the
        //    release), but the pin and unpin of the cursor must occur under the collection lock.
        //    We don't use our AutoGetCollectionForRead "ctx" to relock, because
        //    AutoGetCollectionForRead checks the sharding version (and we want the relock for the
        //    unpin to succeed even if the sharding version has changed).
        //
        // Note that we declare our locks before our ClientCursorPin, in order to ensure that the
        // pin's destructor is called before the lock destructors (so that the unpin occurs under
        // the lock).
        boost::scoped_ptr<AutoGetCollectionForRead> ctx;
        boost::scoped_ptr<Lock::DBLock> unpinDBLock;
        boost::scoped_ptr<Lock::CollectionLock> unpinCollLock;

        CursorManager* cursorManager;
        CursorManager* globalCursorManager = CursorManager::getGlobalCursorManager();
        if (globalCursorManager->ownsCursorId(cursorid)) {
            cursorManager = globalCursorManager;
        }
        else {
            ctx.reset(new AutoGetCollectionForRead(txn, nss));
            Collection* collection = ctx->getCollection();
            uassert( 17356, "collection dropped between getMore calls", collection );
            cursorManager = collection->getCursorManager();
        }

        LOG(5) << "Running getMore, cursorid: " << cursorid << endl;

        // This checks to make sure the operation is allowed on a replicated node.  Since we are not
        // passing in a query object (necessary to check SlaveOK query option), the only state where
        // reads are allowed is PRIMARY (or master in master/slave).  This function uasserts if
        // reads are not okay.
        Status status = repl::getGlobalReplicationCoordinator()->checkCanServeReadsFor(
                txn,
                nss,
                true);
        uassertStatusOK(status);

        // A pin performs a CC lookup and if there is a CC, increments the CC's pin value so it
        // doesn't time out.  Also informs ClientCursor that there is somebody actively holding the
        // CC, so don't delete it.
        ClientCursorPin ccPin(cursorManager, cursorid);
        ClientCursor* cc = ccPin.c();

        // If we're not being called from DBDirectClient we want to associate the RecoveryUnit
        // used to create the execution machinery inside the cursor with our OperationContext.
        // If we throw or otherwise exit this method in a disorderly fashion, we must ensure
        // that further calls to getMore won't fail, and that the provided OperationContext
        // has a valid RecoveryUnit.  As such, we use RAII to accomplish this.
        //
        // This must be destroyed before the ClientCursor is destroyed.
        std::auto_ptr<ScopedRecoveryUnitSwapper> ruSwapper;

        // These are set in the QueryResult msg we return.
        int resultFlags = ResultFlag_AwaitCapable;

        int numResults = 0;
        int startingResult = 0;

        const int InitialBufSize =
            512 + sizeof(QueryResult::Value) + MaxBytesToReturnToClientAtOnce;

        BufBuilder bb(InitialBufSize);
        bb.skip(sizeof(QueryResult::Value));

        if (NULL == cc) {
            cursorid = 0;
            resultFlags = ResultFlag_CursorNotFound;
        }
        else {
            // Check for spoofing of the ns such that it does not match the one originally
            // there for the cursor.
            uassert(ErrorCodes::Unauthorized,
                    str::stream() << "Requested getMore on namespace " << ns << ", but cursor "
                                  << cursorid << " belongs to namespace " << cc->ns(),
                    ns == cc->ns());
            *isCursorAuthorized = true;

            // Restore the RecoveryUnit if we need to.
            if (txn->getClient()->isInDirectClient()) {
                if (cc->hasRecoveryUnit())
                    invariant(txn->recoveryUnit() == cc->getUnownedRecoveryUnit());
            }
            else {
                if (!cc->hasRecoveryUnit()) {
                    // Start using a new RecoveryUnit
                    cc->setOwnedRecoveryUnit(
                        getGlobalServiceContext()->getGlobalStorageEngine()->newRecoveryUnit());

                }
                // Swap RecoveryUnit(s) between the ClientCursor and OperationContext.
                ruSwapper.reset(new ScopedRecoveryUnitSwapper(cc, txn));
            }

            // Reset timeout timer on the cursor since the cursor is still in use.
            cc->setIdleTime(0);

            // If the operation that spawned this cursor had a time limit set, apply leftover
            // time to this getmore.
            curop.setMaxTimeMicros(cc->getLeftoverMaxTimeMicros());
            txn->checkForInterrupt(); // May trigger maxTimeAlwaysTimeOut fail point.

            if (0 == pass) { 
                cc->updateSlaveLocation(txn); 
            }

            if (cc->isAggCursor()) {
                // Agg cursors handle their own locking internally.
                ctx.reset(); // unlocks
            }

            // If we're replaying the oplog, we save the last time that we read.
            Timestamp slaveReadTill;

            // What number result are we starting at?  Used to fill out the reply.
            startingResult = cc->pos();

            // What gives us results.
            PlanExecutor* exec = cc->getExecutor();
            const int queryOptions = cc->queryOptions();

            // Get results out of the executor.
            exec->restoreState(txn);

            BSONObj obj;
            PlanExecutor::ExecState state;
            while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
                // Add result to output buffer.
                bb.appendBuf((void*)obj.objdata(), obj.objsize());

                // Count the result.
                ++numResults;

                // Possibly note slave's position in the oplog.
                if (queryOptions & QueryOption_OplogReplay) {
                    BSONElement e = obj["ts"];
                    if (Date == e.type() || bsonTimestamp == e.type()) {
                        slaveReadTill = e.timestamp();
                    }
                }

                if (enoughForGetMore(ntoreturn, numResults, bb.len())) {
                    break;
                }
            }

            if (PlanExecutor::DEAD == state || PlanExecutor::FAILURE == state) {
                // Propagate this error to caller.
                if (PlanExecutor::FAILURE == state) {
                    scoped_ptr<PlanStageStats> stats(exec->getStats());
                    error() << "Plan executor error, stats: "
                            << Explain::statsToBSON(*stats);
                    uasserted(17406, "getMore executor error: " +
                              WorkingSetCommon::toStatusString(obj));
                }

                // In the old system tailable capped cursors would be killed off at the
                // cursorid level.  If a tailable capped cursor is nuked the cursorid
                // would vanish.
                //
                // In the new system they die and are cleaned up later (or time out).
                // So this is where we get to remove the cursorid.
                if (0 == numResults) {
                    resultFlags = ResultFlag_CursorNotFound;
                }
            }

            const bool shouldSaveCursor =
                    shouldSaveCursorGetMore(state, exec, isCursorTailable(cc));

            // In order to deregister a cursor, we need to be holding the DB + collection lock and
            // if the cursor is aggregation, we release these locks.
            if (cc->isAggCursor()) {
                invariant(NULL == ctx.get());
                unpinDBLock.reset(new Lock::DBLock(txn->lockState(), nss.db(), MODE_IS));
                unpinCollLock.reset(new Lock::CollectionLock(txn->lockState(), nss.ns(), MODE_IS));
            }

            // Our two possible ClientCursorPin cleanup paths are:
            // 1) If the cursor is not going to be saved, we call deleteUnderlying() on the pin.
            // 2) If the cursor is going to be saved, we simply let the pin go out of scope.  In
            //    this case, the pin's destructor will be invoked, which will call release() on the
            //    pin.  Because our ClientCursorPin is declared after our lock is declared, this
            //    will happen under the lock.
            if (!shouldSaveCursor) {
                ruSwapper.reset();
                ccPin.deleteUnderlying();

                // cc is now invalid, as is the executor
                cursorid = 0;
                cc = NULL;
                curop.debug().cursorExhausted = true;

                LOG(5) << "getMore NOT saving client cursor, ended with state "
                       << PlanExecutor::statestr(state)
                       << endl;
            }
            else {
                // Continue caching the ClientCursor.
                cc->incPos(numResults);
                exec->saveState();
                LOG(5) << "getMore saving client cursor ended with state "
                       << PlanExecutor::statestr(state)
                       << endl;

                if (PlanExecutor::IS_EOF == state && (queryOptions & QueryOption_CursorTailable)) {
                    if (!txn->getClient()->isInDirectClient()) {
                        // Don't stash the RU. Get a new one on the next getMore.
                        ruSwapper->dismiss();
                    }

                    if ((queryOptions & QueryOption_AwaitData)
                            && (numResults == 0)
                            && (pass < 1000)) {
                        // Bubble up to the AwaitData handling code in receivedGetMore which will
                        // try again.
                        return NULL;
                    }
                }

                // Possibly note slave's position in the oplog.
                if ((queryOptions & QueryOption_OplogReplay) && !slaveReadTill.isNull()) {
                    cc->slaveReadTill(slaveReadTill);
                }

                exhaust = (queryOptions & QueryOption_Exhaust);

                // If the getmore had a time limit, remaining time is "rolled over" back to the
                // cursor (for use by future getmore ops).
                cc->setLeftoverMaxTimeMicros( curop.getRemainingMaxTimeMicros() );
            }
        }

        QueryResult::View qr = bb.buf();
        qr.msgdata().setLen(bb.len());
        qr.msgdata().setOperation(opReply);
        qr.setResultFlags(resultFlags);
        qr.setCursorId(cursorid);
        qr.setStartingFrom(startingResult);
        qr.setNReturned(numResults);
        bb.decouple();
        LOG(5) << "getMore returned " << numResults << " results\n";
        return qr;
    }
Пример #12
0
/**
 * Called by db/instance.cpp.  This is the getMore entry point.
 */
QueryResult::View getMore(OperationContext* txn,
                          const char* ns,
                          int ntoreturn,
                          long long cursorid,
                          bool* exhaust,
                          bool* isCursorAuthorized) {
    invariant(ntoreturn >= 0);

    CurOp& curop = *CurOp::get(txn);

    // For testing, we may want to fail if we receive a getmore.
    if (MONGO_FAIL_POINT(failReceivedGetmore)) {
        invariant(0);
    }

    *exhaust = false;

    const NamespaceString nss(ns);

    // Depending on the type of cursor being operated on, we hold locks for the whole getMore,
    // or none of the getMore, or part of the getMore.  The three cases in detail:
    //
    // 1) Normal cursor: we lock with "ctx" and hold it for the whole getMore.
    // 2) Cursor owned by global cursor manager: we don't lock anything.  These cursors don't own
    //    any collection state. These cursors are generated either by the listCollections or
    //    listIndexes commands, as these special cursor-generating commands operate over catalog
    //    data rather than targeting the data within a collection.
    // 3) Agg cursor: we lock with "ctx", then release, then relock with "unpinDBLock" and
    //    "unpinCollLock".  This is because agg cursors handle locking internally (hence the
    //    release), but the pin and unpin of the cursor must occur under the collection lock.
    //    We don't use our AutoGetCollectionForRead "ctx" to relock, because
    //    AutoGetCollectionForRead checks the sharding version (and we want the relock for the
    //    unpin to succeed even if the sharding version has changed).
    //
    // Note that we declare our locks before our ClientCursorPin, in order to ensure that the
    // pin's destructor is called before the lock destructors (so that the unpin occurs under
    // the lock).
    unique_ptr<AutoGetCollectionForRead> ctx;
    unique_ptr<Lock::DBLock> unpinDBLock;
    unique_ptr<Lock::CollectionLock> unpinCollLock;

    CursorManager* cursorManager;
    if (nss.isListIndexesCursorNS() || nss.isListCollectionsCursorNS()) {
        // List collections and list indexes are special cursor-generating commands whose
        // cursors are managed globally, as they operate over catalog data rather than targeting
        // the data within a collection.
        cursorManager = CursorManager::getGlobalCursorManager();
    } else {
        ctx = stdx::make_unique<AutoGetCollectionForRead>(txn, nss);
        Collection* collection = ctx->getCollection();
        uassert(17356, "collection dropped between getMore calls", collection);
        cursorManager = collection->getCursorManager();
    }

    LOG(5) << "Running getMore, cursorid: " << cursorid << endl;

    // This checks to make sure the operation is allowed on a replicated node.  Since we are not
    // passing in a query object (necessary to check SlaveOK query option), the only state where
    // reads are allowed is PRIMARY (or master in master/slave).  This function uasserts if
    // reads are not okay.
    Status status = repl::getGlobalReplicationCoordinator()->checkCanServeReadsFor(txn, nss, true);
    uassertStatusOK(status);

    // A pin performs a CC lookup and if there is a CC, increments the CC's pin value so it
    // doesn't time out.  Also informs ClientCursor that there is somebody actively holding the
    // CC, so don't delete it.
    ClientCursorPin ccPin(cursorManager, cursorid);
    ClientCursor* cc = ccPin.c();
    // These are set in the QueryResult msg we return.
    int resultFlags = ResultFlag_AwaitCapable;

    int numResults = 0;
    int startingResult = 0;

    const int InitialBufSize =
        512 + sizeof(QueryResult::Value) + FindCommon::kMaxBytesToReturnToClientAtOnce;

    BufBuilder bb(InitialBufSize);
    bb.skip(sizeof(QueryResult::Value));

    if (NULL == cc) {
        cursorid = 0;
        resultFlags = ResultFlag_CursorNotFound;
    } else {
        // Check for spoofing of the ns such that it does not match the one originally
        // there for the cursor.
        uassert(ErrorCodes::Unauthorized,
                str::stream() << "Requested getMore on namespace " << ns << ", but cursor "
                              << cursorid << " belongs to namespace " << cc->ns(),
                ns == cc->ns());
        *isCursorAuthorized = true;

        if (cc->isReadCommitted())
            uassertStatusOK(txn->recoveryUnit()->setReadFromMajorityCommittedSnapshot());

        // Reset timeout timer on the cursor since the cursor is still in use.
        cc->setIdleTime(0);

        // If the operation that spawned this cursor had a time limit set, apply leftover
        // time to this getmore.
        curop.setMaxTimeMicros(cc->getLeftoverMaxTimeMicros());
        txn->checkForInterrupt();  // May trigger maxTimeAlwaysTimeOut fail point.

        // Ensure that the original query or command object is available in the slow query log,
        // profiler, and currentOp.
        curop.debug().query = cc->getQuery();
        {
            stdx::lock_guard<Client> lk(*txn->getClient());
            curop.setQuery_inlock(cc->getQuery());
        }

        cc->updateSlaveLocation(txn);

        if (cc->isAggCursor()) {
            // Agg cursors handle their own locking internally.
            ctx.reset();  // unlocks
        }

        // If we're replaying the oplog, we save the last time that we read.
        Timestamp slaveReadTill;

        // What number result are we starting at?  Used to fill out the reply.
        startingResult = cc->pos();

        uint64_t notifierVersion = 0;
        std::shared_ptr<CappedInsertNotifier> notifier;
        if (isCursorAwaitData(cc)) {
            invariant(ctx->getCollection()->isCapped());
            // Retrieve the notifier which we will wait on until new data arrives. We make sure
            // to do this in the lock because once we drop the lock it is possible for the
            // collection to become invalid. The notifier itself will outlive the collection if
            // the collection is dropped, as we keep a shared_ptr to it.
            notifier = ctx->getCollection()->getCappedInsertNotifier();

            // Must get the version before we call generateBatch in case a write comes in after
            // that call and before we call wait on the notifier.
            notifierVersion = notifier->getVersion();
        }

        PlanExecutor* exec = cc->getExecutor();
        exec->reattachToOperationContext(txn);
        exec->restoreState();
        PlanExecutor::ExecState state;

        generateBatch(ntoreturn, cc, &bb, &numResults, &slaveReadTill, &state);

        // If this is an await data cursor, and we hit EOF without generating any results, then
        // we block waiting for new data to arrive.
        if (isCursorAwaitData(cc) && state == PlanExecutor::IS_EOF && numResults == 0) {
            // Save the PlanExecutor and drop our locks.
            exec->saveState();
            ctx.reset();

            // Block waiting for data for up to 1 second.
            Seconds timeout(1);
            notifier->wait(notifierVersion, timeout);
            notifier.reset();

            // Set expected latency to match wait time. This makes sure the logs aren't spammed
            // by awaitData queries that exceed slowms due to blocking on the CappedInsertNotifier.
            curop.setExpectedLatencyMs(durationCount<Milliseconds>(timeout));

            // Reacquiring locks.
            ctx = make_unique<AutoGetCollectionForRead>(txn, nss);
            exec->restoreState();

            // We woke up because either the timed_wait expired, or there was more data. Either
            // way, attempt to generate another batch of results.
            generateBatch(ntoreturn, cc, &bb, &numResults, &slaveReadTill, &state);
        }

        // We have to do this before re-acquiring locks in the agg case because
        // shouldSaveCursorGetMore() can make a network call for agg cursors.
        //
        // TODO: Getting rid of PlanExecutor::isEOF() in favor of PlanExecutor::IS_EOF would mean
        // that this network operation is no longer necessary.
        const bool shouldSaveCursor = shouldSaveCursorGetMore(state, exec, isCursorTailable(cc));

        // In order to deregister a cursor, we need to be holding the DB + collection lock and
        // if the cursor is aggregation, we release these locks.
        if (cc->isAggCursor()) {
            invariant(NULL == ctx.get());
            unpinDBLock = make_unique<Lock::DBLock>(txn->lockState(), nss.db(), MODE_IS);
            unpinCollLock = make_unique<Lock::CollectionLock>(txn->lockState(), nss.ns(), MODE_IS);
        }

        // Our two possible ClientCursorPin cleanup paths are:
        // 1) If the cursor is not going to be saved, we call deleteUnderlying() on the pin.
        // 2) If the cursor is going to be saved, we simply let the pin go out of scope.  In
        //    this case, the pin's destructor will be invoked, which will call release() on the
        //    pin.  Because our ClientCursorPin is declared after our lock is declared, this
        //    will happen under the lock.
        if (!shouldSaveCursor) {
            ccPin.deleteUnderlying();

            // cc is now invalid, as is the executor
            cursorid = 0;
            cc = NULL;
            curop.debug().cursorExhausted = true;

            LOG(5) << "getMore NOT saving client cursor, ended with state "
                   << PlanExecutor::statestr(state) << endl;
        } else {
            // Continue caching the ClientCursor.
            cc->incPos(numResults);
            exec->saveState();
            exec->detachFromOperationContext();
            LOG(5) << "getMore saving client cursor ended with state "
                   << PlanExecutor::statestr(state) << endl;

            // Possibly note slave's position in the oplog.
            if ((cc->queryOptions() & QueryOption_OplogReplay) && !slaveReadTill.isNull()) {
                cc->slaveReadTill(slaveReadTill);
            }

            *exhaust = cc->queryOptions() & QueryOption_Exhaust;

            // If the getmore had a time limit, remaining time is "rolled over" back to the
            // cursor (for use by future getmore ops).
            cc->setLeftoverMaxTimeMicros(curop.getRemainingMaxTimeMicros());
        }
    }

    QueryResult::View qr = bb.buf();
    qr.msgdata().setLen(bb.len());
    qr.msgdata().setOperation(opReply);
    qr.setResultFlags(resultFlags);
    qr.setCursorId(cursorid);
    qr.setStartingFrom(startingResult);
    qr.setNReturned(numResults);
    bb.decouple();
    LOG(5) << "getMore returned " << numResults << " results\n";
    return qr;
}
Пример #13
0
std::string runQuery(OperationContext* txn,
                     QueryMessage& q,
                     const NamespaceString& nss,
                     Message& result) {
    CurOp& curop = *CurOp::get(txn);

    uassert(ErrorCodes::InvalidNamespace,
            str::stream() << "Invalid ns [" << nss.ns() << "]",
            nss.isValid());
    invariant(!nss.isCommand());

    // Set curop information.
    beginQueryOp(txn, nss, q.query, q.ntoreturn, q.ntoskip);

    // Parse the qm into a CanonicalQuery.

    auto statusWithCQ = CanonicalQuery::canonicalize(q, ExtensionsCallbackReal(txn, &nss));
    if (!statusWithCQ.isOK()) {
        uasserted(
            17287,
            str::stream() << "Can't canonicalize query: " << statusWithCQ.getStatus().toString());
    }
    unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
    invariant(cq.get());

    LOG(5) << "Running query:\n" << cq->toString();
    LOG(2) << "Running query: " << cq->toStringShort();

    // Parse, canonicalize, plan, transcribe, and get a plan executor.
    AutoGetCollectionForRead ctx(txn, nss);
    Collection* collection = ctx.getCollection();

    const int dbProfilingLevel =
        ctx.getDb() ? ctx.getDb()->getProfilingLevel() : serverGlobalParams.defaultProfile;

    // We have a parsed query. Time to get the execution plan for it.
    std::unique_ptr<PlanExecutor> exec = uassertStatusOK(
        getExecutorFind(txn, collection, nss, std::move(cq), PlanExecutor::YIELD_AUTO));

    const LiteParsedQuery& pq = exec->getCanonicalQuery()->getParsed();

    // If it's actually an explain, do the explain and return rather than falling through
    // to the normal query execution loop.
    if (pq.isExplain()) {
        BufBuilder bb;
        bb.skip(sizeof(QueryResult::Value));

        BSONObjBuilder explainBob;
        Explain::explainStages(exec.get(), ExplainCommon::EXEC_ALL_PLANS, &explainBob);

        // Add the resulting object to the return buffer.
        BSONObj explainObj = explainBob.obj();
        bb.appendBuf((void*)explainObj.objdata(), explainObj.objsize());

        // TODO: Does this get overwritten/do we really need to set this twice?
        curop.debug().query = q.query;

        // Set query result fields.
        QueryResult::View qr = bb.buf();
        bb.decouple();
        qr.setResultFlagsToOk();
        qr.msgdata().setLen(bb.len());
        curop.debug().responseLength = bb.len();
        qr.msgdata().setOperation(opReply);
        qr.setCursorId(0);
        qr.setStartingFrom(0);
        qr.setNReturned(1);
        result.setData(qr.view2ptr(), true);
        return "";
    }

    // Handle query option $maxTimeMS (not used with commands).
    curop.setMaxTimeMicros(static_cast<unsigned long long>(pq.getMaxTimeMS()) * 1000);
    txn->checkForInterrupt();  // May trigger maxTimeAlwaysTimeOut fail point.

    // uassert if we are not on a primary, and not a secondary with SlaveOk query parameter set.
    bool slaveOK = pq.isSlaveOk() || pq.hasReadPref();
    Status serveReadsStatus =
        repl::getGlobalReplicationCoordinator()->checkCanServeReadsFor(txn, nss, slaveOK);
    uassertStatusOK(serveReadsStatus);

    // Run the query.
    // bb is used to hold query results
    // this buffer should contain either requested documents per query or
    // explain information, but not both
    BufBuilder bb(FindCommon::kInitReplyBufferSize);
    bb.skip(sizeof(QueryResult::Value));

    // How many results have we obtained from the executor?
    int numResults = 0;

    // If we're replaying the oplog, we save the last time that we read.
    Timestamp slaveReadTill;

    BSONObj obj;
    PlanExecutor::ExecState state;

    // Get summary info about which plan the executor is using.
    {
        stdx::lock_guard<Client> lk(*txn->getClient());
        curop.setPlanSummary_inlock(Explain::getPlanSummary(exec.get()));
    }

    while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
        // If we can't fit this result inside the current batch, then we stash it for later.
        if (!FindCommon::haveSpaceForNext(obj, numResults, bb.len())) {
            exec->enqueue(obj);
            break;
        }

        // Add result to output buffer.
        bb.appendBuf((void*)obj.objdata(), obj.objsize());

        // Count the result.
        ++numResults;

        // Possibly note slave's position in the oplog.
        if (pq.isOplogReplay()) {
            BSONElement e = obj["ts"];
            if (Date == e.type() || bsonTimestamp == e.type()) {
                slaveReadTill = e.timestamp();
            }
        }

        if (FindCommon::enoughForFirstBatch(pq, numResults)) {
            LOG(5) << "Enough for first batch, wantMore=" << pq.wantMore()
                   << " ntoreturn=" << pq.getNToReturn().value_or(0) << " numResults=" << numResults
                   << endl;
            break;
        }
    }

    // If we cache the executor later, we want to deregister it as it receives notifications
    // anyway by virtue of being cached.
    //
    // If we don't cache the executor later, we are deleting it, so it must be deregistered.
    //
    // So, no matter what, deregister the executor.
    exec->deregisterExec();

    // Caller expects exceptions thrown in certain cases.
    if (PlanExecutor::FAILURE == state || PlanExecutor::DEAD == state) {
        error() << "Plan executor error during find: " << PlanExecutor::statestr(state)
                << ", stats: " << Explain::getWinningPlanStats(exec.get());
        uasserted(17144, "Executor error: " + WorkingSetCommon::toStatusString(obj));
    }

    // Before saving the cursor, ensure that whatever plan we established happened with the expected
    // collection version
    auto css = CollectionShardingState::get(txn, nss);
    css->checkShardVersionOrThrow(txn);

    // Fill out curop based on query results. If we have a cursorid, we will fill out curop with
    // this cursorid later.
    long long ccId = 0;

    if (shouldSaveCursor(txn, collection, state, exec.get())) {
        // We won't use the executor until it's getMore'd.
        exec->saveState();
        exec->detachFromOperationContext();

        // Allocate a new ClientCursor.  We don't have to worry about leaking it as it's
        // inserted into a global map by its ctor.
        ClientCursor* cc =
            new ClientCursor(collection->getCursorManager(),
                             exec.release(),
                             nss.ns(),
                             txn->recoveryUnit()->isReadingFromMajorityCommittedSnapshot(),
                             pq.getOptions(),
                             pq.getFilter());
        ccId = cc->cursorid();

        LOG(5) << "caching executor with cursorid " << ccId << " after returning " << numResults
               << " results" << endl;

        // TODO document
        if (pq.isOplogReplay() && !slaveReadTill.isNull()) {
            cc->slaveReadTill(slaveReadTill);
        }

        // TODO document
        if (pq.isExhaust()) {
            curop.debug().exhaust = true;
        }

        cc->setPos(numResults);

        // If the query had a time limit, remaining time is "rolled over" to the cursor (for
        // use by future getmore ops).
        cc->setLeftoverMaxTimeMicros(curop.getRemainingMaxTimeMicros());

        endQueryOp(txn, collection, *cc->getExecutor(), dbProfilingLevel, numResults, ccId);
    } else {
        LOG(5) << "Not caching executor but returning " << numResults << " results.\n";
        endQueryOp(txn, collection, *exec, dbProfilingLevel, numResults, ccId);
    }

    // Add the results from the query into the output buffer.
    result.appendData(bb.buf(), bb.len());
    bb.decouple();

    // Fill out the output buffer's header.
    QueryResult::View qr = result.header().view2ptr();
    qr.setCursorId(ccId);
    qr.setResultFlagsToOk();
    qr.msgdata().setOperation(opReply);
    qr.setStartingFrom(0);
    qr.setNReturned(numResults);

    // curop.debug().exhaust is set above.
    return curop.debug().exhaust ? nss.ns() : "";
}
Пример #14
0
std::string runQuery(OperationContext* opCtx,
                     QueryMessage& q,
                     const NamespaceString& nss,
                     Message& result) {
    CurOp& curOp = *CurOp::get(opCtx);
    curOp.ensureStarted();

    uassert(ErrorCodes::InvalidNamespace,
            str::stream() << "Invalid ns [" << nss.ns() << "]",
            nss.isValid());
    invariant(!nss.isCommand());

    // Set CurOp information.
    const auto upconvertedQuery = upconvertQueryEntry(q.query, nss, q.ntoreturn, q.ntoskip);
    beginQueryOp(opCtx, nss, upconvertedQuery, q.ntoreturn, q.ntoskip);

    // Parse the qm into a CanonicalQuery.
    const boost::intrusive_ptr<ExpressionContext> expCtx;
    auto cq = uassertStatusOKWithContext(
        CanonicalQuery::canonicalize(opCtx,
                                     q,
                                     expCtx,
                                     ExtensionsCallbackReal(opCtx, &nss),
                                     MatchExpressionParser::kAllowAllSpecialFeatures),
        "Can't canonicalize query");
    invariant(cq.get());

    LOG(5) << "Running query:\n" << redact(cq->toString());
    LOG(2) << "Running query: " << redact(cq->toStringShort());

    // Parse, canonicalize, plan, transcribe, and get a plan executor.
    AutoGetCollectionForReadCommand ctx(opCtx, nss, AutoGetCollection::ViewMode::kViewsForbidden);
    Collection* const collection = ctx.getCollection();

    {
        const QueryRequest& qr = cq->getQueryRequest();

        // Allow the query to run on secondaries if the read preference permits it. If no read
        // preference was specified, allow the query to run iff slaveOk has been set.
        const bool slaveOK = qr.hasReadPref()
            ? uassertStatusOK(ReadPreferenceSetting::fromContainingBSON(q.query))
                  .canRunOnSecondary()
            : qr.isSlaveOk();
        uassertStatusOK(
            repl::ReplicationCoordinator::get(opCtx)->checkCanServeReadsFor(opCtx, nss, slaveOK));
    }

    // We have a parsed query. Time to get the execution plan for it.
    auto exec = uassertStatusOK(getExecutorLegacyFind(opCtx, collection, nss, std::move(cq)));

    const QueryRequest& qr = exec->getCanonicalQuery()->getQueryRequest();

    // If it's actually an explain, do the explain and return rather than falling through
    // to the normal query execution loop.
    if (qr.isExplain()) {
        BufBuilder bb;
        bb.skip(sizeof(QueryResult::Value));

        BSONObjBuilder explainBob;
        Explain::explainStages(
            exec.get(), collection, ExplainOptions::Verbosity::kExecAllPlans, &explainBob);

        // Add the resulting object to the return buffer.
        BSONObj explainObj = explainBob.obj();
        bb.appendBuf((void*)explainObj.objdata(), explainObj.objsize());

        // Set query result fields.
        QueryResult::View qr = bb.buf();
        qr.setResultFlagsToOk();
        qr.msgdata().setLen(bb.len());
        curOp.debug().responseLength = bb.len();
        qr.msgdata().setOperation(opReply);
        qr.setCursorId(0);
        qr.setStartingFrom(0);
        qr.setNReturned(1);
        result.setData(bb.release());
        return "";
    }

    // Handle query option $maxTimeMS (not used with commands).
    if (qr.getMaxTimeMS() > 0) {
        uassert(40116,
                "Illegal attempt to set operation deadline within DBDirectClient",
                !opCtx->getClient()->isInDirectClient());
        opCtx->setDeadlineAfterNowBy(Milliseconds{qr.getMaxTimeMS()});
    }
    opCtx->checkForInterrupt();  // May trigger maxTimeAlwaysTimeOut fail point.

    // Run the query.
    // bb is used to hold query results
    // this buffer should contain either requested documents per query or
    // explain information, but not both
    BufBuilder bb(FindCommon::kInitReplyBufferSize);
    bb.skip(sizeof(QueryResult::Value));

    // How many results have we obtained from the executor?
    int numResults = 0;

    BSONObj obj;
    PlanExecutor::ExecState state;

    // Get summary info about which plan the executor is using.
    {
        stdx::lock_guard<Client> lk(*opCtx->getClient());
        curOp.setPlanSummary_inlock(Explain::getPlanSummary(exec.get()));
    }

    while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
        // If we can't fit this result inside the current batch, then we stash it for later.
        if (!FindCommon::haveSpaceForNext(obj, numResults, bb.len())) {
            exec->enqueue(obj);
            break;
        }

        // Add result to output buffer.
        bb.appendBuf((void*)obj.objdata(), obj.objsize());

        // Count the result.
        ++numResults;

        if (FindCommon::enoughForFirstBatch(qr, numResults)) {
            LOG(5) << "Enough for first batch, wantMore=" << qr.wantMore()
                   << " ntoreturn=" << qr.getNToReturn().value_or(0)
                   << " numResults=" << numResults;
            break;
        }
    }

    // Caller expects exceptions thrown in certain cases.
    if (PlanExecutor::FAILURE == state || PlanExecutor::DEAD == state) {
        error() << "Plan executor error during find: " << PlanExecutor::statestr(state)
                << ", stats: " << redact(Explain::getWinningPlanStats(exec.get()));
        uassertStatusOKWithContext(WorkingSetCommon::getMemberObjectStatus(obj),
                                   "Executor error during OP_QUERY find");
        MONGO_UNREACHABLE;
    }

    // Before saving the cursor, ensure that whatever plan we established happened with the expected
    // collection version
    auto css = CollectionShardingState::get(opCtx, nss);
    css->checkShardVersionOrThrow(opCtx);

    // Fill out CurOp based on query results. If we have a cursorid, we will fill out CurOp with
    // this cursorid later.
    long long ccId = 0;

    if (shouldSaveCursor(opCtx, collection, state, exec.get())) {
        // We won't use the executor until it's getMore'd.
        exec->saveState();
        exec->detachFromOperationContext();

        // Allocate a new ClientCursor and register it with the cursor manager.
        ClientCursorPin pinnedCursor = collection->getCursorManager()->registerCursor(
            opCtx,
            {std::move(exec),
             nss,
             AuthorizationSession::get(opCtx->getClient())->getAuthenticatedUserNames(),
             opCtx->recoveryUnit()->getReadConcernLevel(),
             upconvertedQuery});
        ccId = pinnedCursor.getCursor()->cursorid();

        LOG(5) << "caching executor with cursorid " << ccId << " after returning " << numResults
               << " results";

        // TODO document
        if (qr.isExhaust()) {
            curOp.debug().exhaust = true;
        }

        pinnedCursor.getCursor()->setPos(numResults);

        // We assume that cursors created through a DBDirectClient are always used from their
        // original OperationContext, so we do not need to move time to and from the cursor.
        if (!opCtx->getClient()->isInDirectClient()) {
            // If the query had a time limit, remaining time is "rolled over" to the cursor (for
            // use by future getmore ops).
            pinnedCursor.getCursor()->setLeftoverMaxTimeMicros(opCtx->getRemainingMaxTimeMicros());
        }

        endQueryOp(opCtx, collection, *pinnedCursor.getCursor()->getExecutor(), numResults, ccId);
    } else {
        LOG(5) << "Not caching executor but returning " << numResults << " results.";
        endQueryOp(opCtx, collection, *exec, numResults, ccId);
    }

    // Fill out the output buffer's header.
    QueryResult::View queryResultView = bb.buf();
    queryResultView.setCursorId(ccId);
    queryResultView.setResultFlagsToOk();
    queryResultView.msgdata().setLen(bb.len());
    queryResultView.msgdata().setOperation(opReply);
    queryResultView.setStartingFrom(0);
    queryResultView.setNReturned(numResults);

    // Add the results from the query into the output buffer.
    result.setData(bb.release());

    // curOp.debug().exhaust is set above.
    return curOp.debug().exhaust ? nss.ns() : "";
}
Пример #15
0
/**
 * Called by db/instance.cpp.  This is the getMore entry point.
 */
Message getMore(OperationContext* opCtx,
                const char* ns,
                int ntoreturn,
                long long cursorid,
                bool* exhaust,
                bool* isCursorAuthorized) {
    invariant(ntoreturn >= 0);

    CurOp& curOp = *CurOp::get(opCtx);
    curOp.ensureStarted();

    // For testing, we may want to fail if we receive a getmore.
    if (MONGO_FAIL_POINT(failReceivedGetmore)) {
        MONGO_UNREACHABLE;
    }

    *exhaust = false;

    const NamespaceString nss(ns);

    // Cursors come in one of two flavors:
    // - Cursors owned by the collection cursor manager, such as those generated via the find
    //   command. For these cursors, we hold the appropriate collection lock for the duration of the
    //   getMore using AutoGetCollectionForRead.
    // - Cursors owned by the global cursor manager, such as those generated via the aggregate
    //   command. These cursors either hold no collection state or manage their collection state
    //   internally, so we acquire no locks.
    //
    // While we only need to acquire locks in the case of a cursor which is *not* globally owned, we
    // need to create an AutoStatsTracker in either case. This is responsible for updating
    // statistics in CurOp and Top. We avoid using AutoGetCollectionForReadCommand because we may
    // need to drop and reacquire locks when the cursor is awaitData, but we don't want to update
    // the stats twice.
    //
    // Note that we acquire our locks before our ClientCursorPin, in order to ensure that the pin's
    // destructor is called before the lock's destructor (if there is one) so that the cursor
    // cleanup can occur under the lock.
    UninterruptibleLockGuard noInterrupt(opCtx->lockState());
    boost::optional<AutoGetCollectionForRead> readLock;
    boost::optional<AutoStatsTracker> statsTracker;
    CursorManager* cursorManager;

    if (CursorManager::isGloballyManagedCursor(cursorid)) {
        cursorManager = CursorManager::getGlobalCursorManager();

        if (boost::optional<NamespaceString> nssForCurOp = nss.isGloballyManagedNamespace()
                ? nss.getTargetNSForGloballyManagedNamespace()
                : nss) {
            AutoGetDb autoDb(opCtx, nssForCurOp->db(), MODE_IS);
            const auto profilingLevel = autoDb.getDb()
                ? boost::optional<int>{autoDb.getDb()->getProfilingLevel()}
                : boost::none;
            statsTracker.emplace(opCtx, *nssForCurOp, Top::LockType::NotLocked, profilingLevel);
            auto view = autoDb.getDb()
                ? autoDb.getDb()->getViewCatalog()->lookup(opCtx, nssForCurOp->ns())
                : nullptr;
            uassert(
                ErrorCodes::CommandNotSupportedOnView,
                str::stream() << "Namespace " << nssForCurOp->ns()
                              << " is a view. OP_GET_MORE operations are not supported on views. "
                              << "Only clients which support the getMore command can be used to "
                                 "query views.",
                !view);
        }
    } else {
        readLock.emplace(opCtx, nss);
        const int doNotChangeProfilingLevel = 0;
        statsTracker.emplace(opCtx,
                             nss,
                             Top::LockType::ReadLocked,
                             readLock->getDb() ? readLock->getDb()->getProfilingLevel()
                                               : doNotChangeProfilingLevel);
        Collection* collection = readLock->getCollection();
        uassert(
            ErrorCodes::OperationFailed, "collection dropped between getMore calls", collection);
        cursorManager = collection->getCursorManager();

        // This checks to make sure the operation is allowed on a replicated node.  Since we are not
        // passing in a query object (necessary to check SlaveOK query option), we allow reads
        // whether we are PRIMARY or SECONDARY.
        uassertStatusOK(
            repl::ReplicationCoordinator::get(opCtx)->checkCanServeReadsFor(opCtx, nss, true));
    }

    LOG(5) << "Running getMore, cursorid: " << cursorid;

    // A pin performs a CC lookup and if there is a CC, increments the CC's pin value so it
    // doesn't time out.  Also informs ClientCursor that there is somebody actively holding the
    // CC, so don't delete it.
    auto ccPin = cursorManager->pinCursor(opCtx, cursorid);

    // These are set in the QueryResult msg we return.
    int resultFlags = ResultFlag_AwaitCapable;

    int numResults = 0;
    int startingResult = 0;

    const int InitialBufSize =
        512 + sizeof(QueryResult::Value) + FindCommon::kMaxBytesToReturnToClientAtOnce;

    BufBuilder bb(InitialBufSize);
    bb.skip(sizeof(QueryResult::Value));

    if (!ccPin.isOK()) {
        if (ccPin == ErrorCodes::CursorNotFound) {
            cursorid = 0;
            resultFlags = ResultFlag_CursorNotFound;
        } else {
            uassertStatusOK(ccPin.getStatus());
        }
    } else {
        ClientCursor* cc = ccPin.getValue().getCursor();

        // Check for spoofing of the ns such that it does not match the one originally
        // there for the cursor.
        uassert(ErrorCodes::Unauthorized,
                str::stream() << "Requested getMore on namespace " << ns << ", but cursor "
                              << cursorid
                              << " belongs to namespace "
                              << cc->nss().ns(),
                nss == cc->nss());

        // A user can only call getMore on their own cursor. If there were multiple users
        // authenticated when the cursor was created, then at least one of them must be
        // authenticated in order to run getMore on the cursor.
        uassert(ErrorCodes::Unauthorized,
                str::stream() << "cursor id " << cursorid
                              << " was not created by the authenticated user",
                AuthorizationSession::get(opCtx->getClient())
                    ->isCoauthorizedWith(cc->getAuthenticatedUsers()));

        *isCursorAuthorized = true;

        const auto replicationMode = repl::ReplicationCoordinator::get(opCtx)->getReplicationMode();
        opCtx->recoveryUnit()->setReadConcernLevelAndReplicationMode(cc->getReadConcernLevel(),
                                                                     replicationMode);

        // TODO SERVER-33698: Remove kSnapshotReadConcern clause once we can guarantee that a
        // readConcern level snapshot getMore will have an established point-in-time WiredTiger
        // snapshot.
        if (replicationMode == repl::ReplicationCoordinator::modeReplSet &&
            (cc->getReadConcernLevel() == repl::ReadConcernLevel::kMajorityReadConcern ||
             cc->getReadConcernLevel() == repl::ReadConcernLevel::kSnapshotReadConcern)) {
            uassertStatusOK(opCtx->recoveryUnit()->obtainMajorityCommittedSnapshot());
        }

        uassert(40548,
                "OP_GET_MORE operations are not supported on tailable aggregations. Only clients "
                "which support the getMore command can be used on tailable aggregations.",
                readLock || !cc->isAwaitData());

        // If the operation that spawned this cursor had a time limit set, apply leftover
        // time to this getmore.
        if (cc->getLeftoverMaxTimeMicros() < Microseconds::max()) {
            uassert(40136,
                    "Illegal attempt to set operation deadline within DBDirectClient",
                    !opCtx->getClient()->isInDirectClient());
            opCtx->setDeadlineAfterNowBy(cc->getLeftoverMaxTimeMicros());
        }
        opCtx->checkForInterrupt();  // May trigger maxTimeAlwaysTimeOut fail point.

        // What number result are we starting at?  Used to fill out the reply.
        startingResult = cc->pos();

        uint64_t notifierVersion = 0;
        std::shared_ptr<CappedInsertNotifier> notifier;
        if (cc->isAwaitData()) {
            invariant(readLock->getCollection()->isCapped());
            // Retrieve the notifier which we will wait on until new data arrives. We make sure
            // to do this in the lock because once we drop the lock it is possible for the
            // collection to become invalid. The notifier itself will outlive the collection if
            // the collection is dropped, as we keep a shared_ptr to it.
            notifier = readLock->getCollection()->getCappedInsertNotifier();

            // Must get the version before we call generateBatch in case a write comes in after
            // that call and before we call wait on the notifier.
            notifierVersion = notifier->getVersion();
        }

        PlanExecutor* exec = cc->getExecutor();
        exec->reattachToOperationContext(opCtx);
        uassertStatusOK(exec->restoreState());

        auto planSummary = Explain::getPlanSummary(exec);
        {
            stdx::lock_guard<Client> lk(*opCtx->getClient());
            curOp.setPlanSummary_inlock(planSummary);

            // Ensure that the original query object is available in the slow query log, profiler
            // and currentOp. Upconvert _query to resemble a getMore command, and set the original
            // command or upconverted legacy query in the originatingCommand field.
            curOp.setOpDescription_inlock(upconvertGetMoreEntry(nss, cursorid, ntoreturn));
            curOp.setOriginatingCommand_inlock(cc->getOriginatingCommandObj());
        }

        PlanExecutor::ExecState state;

        // We report keysExamined and docsExamined to OpDebug for a given getMore operation. To
        // obtain these values we need to take a diff of the pre-execution and post-execution
        // metrics, as they accumulate over the course of a cursor's lifetime.
        PlanSummaryStats preExecutionStats;
        Explain::getSummaryStats(*exec, &preExecutionStats);

        generateBatch(ntoreturn, cc, &bb, &numResults, &state);

        // If this is an await data cursor, and we hit EOF without generating any results, then
        // we block waiting for new data to arrive.
        if (cc->isAwaitData() && state == PlanExecutor::IS_EOF && numResults == 0) {
            // Save the PlanExecutor and drop our locks.
            exec->saveState();
            readLock.reset();

            // Block waiting for data for up to 1 second. Time spent blocking is not counted towards
            // the total operation latency.
            curOp.pauseTimer();
            Seconds timeout(1);
            notifier->waitUntil(notifierVersion,
                                opCtx->getServiceContext()->getPreciseClockSource()->now() +
                                    timeout);
            notifier.reset();
            curOp.resumeTimer();

            // Reacquiring locks.
            readLock.emplace(opCtx, nss);
            uassertStatusOK(exec->restoreState());

            // We woke up because either the timed_wait expired, or there was more data. Either
            // way, attempt to generate another batch of results.
            generateBatch(ntoreturn, cc, &bb, &numResults, &state);
        }

        PlanSummaryStats postExecutionStats;
        Explain::getSummaryStats(*exec, &postExecutionStats);
        postExecutionStats.totalKeysExamined -= preExecutionStats.totalKeysExamined;
        postExecutionStats.totalDocsExamined -= preExecutionStats.totalDocsExamined;
        curOp.debug().setPlanSummaryMetrics(postExecutionStats);

        // We do not report 'execStats' for aggregation or other globally managed cursors, both in
        // the original request and subsequent getMore. It would be useful to have this information
        // for an aggregation, but the source PlanExecutor could be destroyed before we know whether
        // we need execStats and we do not want to generate for all operations due to cost.
        if (!CursorManager::isGloballyManagedCursor(cursorid) && curOp.shouldDBProfile()) {
            BSONObjBuilder execStatsBob;
            Explain::getWinningPlanStats(exec, &execStatsBob);
            curOp.debug().execStats = execStatsBob.obj();
        }

        // Our two possible ClientCursorPin cleanup paths are:
        // 1) If the cursor is not going to be saved, we call deleteUnderlying() on the pin.
        // 2) If the cursor is going to be saved, we simply let the pin go out of scope. In this
        //    case, the pin's destructor will be invoked, which will call release() on the pin.
        //    Because our ClientCursorPin is declared after our lock is declared, this will happen
        //    under the lock if any locking was necessary.
        if (!shouldSaveCursorGetMore(state, exec, cc->isTailable())) {
            ccPin.getValue().deleteUnderlying();

            // cc is now invalid, as is the executor
            cursorid = 0;
            cc = nullptr;
            curOp.debug().cursorExhausted = true;

            LOG(5) << "getMore NOT saving client cursor, ended with state "
                   << PlanExecutor::statestr(state);
        } else {
            // Continue caching the ClientCursor.
            cc->incPos(numResults);
            exec->saveState();
            exec->detachFromOperationContext();
            LOG(5) << "getMore saving client cursor ended with state "
                   << PlanExecutor::statestr(state);

            *exhaust = cc->queryOptions() & QueryOption_Exhaust;

            // We assume that cursors created through a DBDirectClient are always used from their
            // original OperationContext, so we do not need to move time to and from the cursor.
            if (!opCtx->getClient()->isInDirectClient()) {
                // If the getmore had a time limit, remaining time is "rolled over" back to the
                // cursor (for use by future getmore ops).
                cc->setLeftoverMaxTimeMicros(opCtx->getRemainingMaxTimeMicros());
            }
        }
    }

    QueryResult::View qr = bb.buf();
    qr.msgdata().setLen(bb.len());
    qr.msgdata().setOperation(opReply);
    qr.setResultFlags(resultFlags);
    qr.setCursorId(cursorid);
    qr.setStartingFrom(startingResult);
    qr.setNReturned(numResults);
    LOG(5) << "getMore returned " << numResults << " results\n";
    return Message(bb.release());
}