void AsyncRequestsSender::_scheduleRequests() {
invariant(!_stopRetrying);
// Schedule remote work on hosts for which we have not sent a request or need to retry.
for (size_t i = 0; i < _remotes.size(); ++i) {
auto& remote = _remotes[i];
// First check if the remote had a retriable error, and if so, clear its response field so
// it will be retried.
if (remote.swResponse && !remote.done) {
// We check both the response status and command status for a retriable error.
Status status = remote.swResponse->getStatus();
if (status.isOK()) {
status = getStatusFromCommandResult(remote.swResponse->getValue().data);
}
if (status.isOK()) {
status = getWriteConcernStatusFromCommandResult(remote.swResponse->getValue().data);
}
if (!status.isOK()) {
// There was an error with either the response or the command.
auto shard = remote.getShard();
if (!shard) {
remote.swResponse =
Status(ErrorCodes::ShardNotFound,
str::stream() << "Could not find shard " << remote.shardId);
} else {
if (remote.shardHostAndPort) {
shard->updateReplSetMonitor(*remote.shardHostAndPort, status);
}
if (shard->isRetriableError(status.code(), _retryPolicy) &&
remote.retryCount < kMaxNumFailedHostRetryAttempts) {
LOG(1) << "Command to remote " << remote.shardId << " at host "
<< *remote.shardHostAndPort
<< " failed with retriable error and will be retried "
<< causedBy(redact(status));
++remote.retryCount;
remote.swResponse.reset();
}
}
}
}
// If the remote does not have a response or pending request, schedule remote work for it.
if (!remote.swResponse && !remote.cbHandle.isValid()) {
auto scheduleStatus = _scheduleRequest(i);
if (!scheduleStatus.isOK()) {
remote.swResponse = std::move(scheduleStatus);
// Push a noop response to the queue to indicate that a remote is ready for
// re-processing due to failure.
_responseQueue.producer.push(boost::none);
}
}
}
}
void AsyncResultsMerger::handleBatchResponse(
const executor::TaskExecutor::RemoteCommandCallbackArgs& cbData, size_t remoteIndex) {
stdx::lock_guard<stdx::mutex> lk(_mutex);
auto& remote = _remotes[remoteIndex];
// Clear the callback handle. This indicates that we are no longer waiting on a response from
// 'remote'.
remote.cbHandle = executor::TaskExecutor::CallbackHandle();
// If we're in the process of shutting down then there's no need to process the batch.
if (_lifecycleState != kAlive) {
invariant(_lifecycleState == kKillStarted);
// Make sure to wake up anyone waiting on '_currentEvent' if we're shutting down.
signalCurrentEventIfReady_inlock();
// Make a best effort to parse the response and retrieve the cursor id. We need the cursor
// id in order to issue a killCursors command against it.
if (cbData.response.isOK()) {
auto cursorResponse = parseCursorResponse(cbData.response.getValue().data, remote);
if (cursorResponse.isOK()) {
remote.cursorId = cursorResponse.getValue().getCursorId();
}
}
// If we're killed and we're not waiting on any more batches to come back, then we are ready
// to kill the cursors on the remote hosts and clean up this cursor. Schedule the
// killCursors command and signal that this cursor is safe now safe to destroy. We have to
// promise not to touch any members of this class because 'this' could become invalid as
// soon as we signal the event.
if (!haveOutstandingBatchRequests_inlock()) {
// If the event handle is invalid, then the executor is in the middle of shutting down,
// and we can't schedule any more work for it to complete.
if (_killCursorsScheduledEvent.isValid()) {
scheduleKillCursors_inlock();
_executor->signalEvent(_killCursorsScheduledEvent);
}
_lifecycleState = kKillComplete;
}
return;
}
// Early return from this point on signal anyone waiting on an event, if ready() is true.
ScopeGuard signaller = MakeGuard(&AsyncResultsMerger::signalCurrentEventIfReady_inlock, this);
StatusWith<CursorResponse> cursorResponseStatus(
cbData.response.isOK() ? parseCursorResponse(cbData.response.getValue().data, remote)
: cbData.response.getStatus());
if (!cursorResponseStatus.isOK()) {
auto shard = remote.getShard();
if (!shard) {
remote.status = Status(cursorResponseStatus.getStatus().code(),
str::stream() << "Could not find shard " << *remote.shardId
<< " containing host "
<< remote.getTargetHost().toString());
} else {
shard->updateReplSetMonitor(remote.getTargetHost(), cursorResponseStatus.getStatus());
// Retry initial cursor establishment if possible. Never retry getMores to avoid
// accidentally skipping results.
if (!remote.cursorId && remote.retryCount < kMaxNumFailedHostRetryAttempts &&
shard->isRetriableError(cursorResponseStatus.getStatus().code(),
Shard::RetryPolicy::kIdempotent)) {
invariant(remote.shardId);
LOG(1) << "Initial cursor establishment failed with retriable error and will be "
"retried"
<< causedBy(redact(cursorResponseStatus.getStatus()));
++remote.retryCount;
// Since we potentially updated the targeter that the last host it chose might be
// faulty, the call below may end up getting a different host.
remote.status = askForNextBatch_inlock(remoteIndex);
if (remote.status.isOK()) {
return;
}
// If we end up here, it means we failed to schedule the retry request, which is a
// more
// severe error that should not be retried. Just pass through to the error handling
// logic below.
} else {
remote.status = cursorResponseStatus.getStatus();
}
}
// Unreachable host errors are swallowed if the 'allowPartialResults' option is set. We
// remove the unreachable host entirely from consideration by marking it as exhausted.
if (_params.isAllowPartialResults) {
remote.status = Status::OK();
// Clear the results buffer and cursor id.
std::queue<BSONObj> emptyBuffer;
std::swap(remote.docBuffer, emptyBuffer);
remote.cursorId = 0;
}
return;
}
// Cursor id successfully established.
auto cursorResponse = std::move(cursorResponseStatus.getValue());
remote.cursorId = cursorResponse.getCursorId();
remote.initialCmdObj = boost::none;
for (const auto& obj : cursorResponse.getBatch()) {
// If there's a sort, we're expecting the remote node to give us back a sort key.
if (!_params.sort.isEmpty() &&
obj[ClusterClientCursorParams::kSortKeyField].type() != BSONType::Object) {
remote.status = Status(ErrorCodes::InternalError,
str::stream() << "Missing field '"
<< ClusterClientCursorParams::kSortKeyField
<< "' in document: "
<< obj);
return;
}
remote.docBuffer.push(obj);
++remote.fetchedCount;
}
// If we're doing a sorted merge, then we have to make sure to put this remote onto the
// merge queue.
if (!_params.sort.isEmpty() && !cursorResponse.getBatch().empty()) {
_mergeQueue.push(remoteIndex);
}
// If the cursor is tailable and we just received an empty batch, the next return value should
// be boost::none in order to indicate the end of the batch.
if (_params.isTailable && !remote.hasNext()) {
_eofNext = true;
}
// If even after receiving this batch we still don't have anything buffered (i.e. the batchSize
// was zero), then can schedule work to retrieve the next batch right away.
//
// We do not ask for the next batch if the cursor is tailable, as batches received from remote
// tailable cursors should be passed through to the client without asking for more batches.
if (!_params.isTailable && !remote.hasNext() && !remote.exhausted()) {
remote.status = askForNextBatch_inlock(remoteIndex);
if (!remote.status.isOK()) {
return;
}
}
// ScopeGuard requires dismiss on success, but we want waiter to be signalled on success as
// well as failure.
signaller.Dismiss();
signalCurrentEventIfReady_inlock();
}