void Balancer::run() {
Client::initThread("Balancer");
// This is the body of a BackgroundJob so if we throw here we're basically ending the balancer
// thread prematurely.
while (!inShutdown()) {
auto txn = cc().makeOperationContext();
if (!_init(txn.get())) {
log() << "will retry to initialize balancer in one minute";
sleepsecs(60);
continue;
}
break;
}
Seconds balanceRoundInterval(kBalanceRoundDefaultInterval);
while (!inShutdown()) {
auto txn = cc().makeOperationContext();
BalanceRoundDetails roundDetails;
try {
// ping has to be first so we keep things in the config server in sync
_ping(txn.get(), false);
MONGO_FAIL_POINT_BLOCK(balancerRoundIntervalSetting, scopedBalancerRoundInterval) {
const BSONObj& data = scopedBalancerRoundInterval.getData();
balanceRoundInterval = Seconds(data["sleepSecs"].numberInt());
}
// Use fresh shard state and balancer settings
Grid::get(txn.get())->shardRegistry()->reload(txn.get());
auto balancerConfig = Grid::get(txn.get())->getBalancerConfiguration();
Status refreshStatus = balancerConfig->refreshAndCheck(txn.get());
if (!refreshStatus.isOK()) {
warning() << "Skipping balancing round" << causedBy(refreshStatus);
sleepFor(balanceRoundInterval);
continue;
}
// now make sure we should even be running
if (!balancerConfig->isBalancerActive() || MONGO_FAIL_POINT(skipBalanceRound)) {
LOG(1) << "skipping balancing round because balancing is disabled";
// Ping again so scripts can determine if we're active without waiting
_ping(txn.get(), true);
sleepFor(balanceRoundInterval);
continue;
}
uassert(13258, "oids broken after resetting!", _checkOIDs(txn.get()));
{
auto scopedDistLock = grid.catalogManager(txn.get())
->distLock(txn.get(),
"balancer",
"doing balance round",
DistLockManager::kSingleLockAttemptTimeout);
if (!scopedDistLock.isOK()) {
LOG(1) << "skipping balancing round" << causedBy(scopedDistLock.getStatus());
// Ping again so scripts can determine if we're active without waiting
_ping(txn.get(), true);
sleepFor(balanceRoundInterval); // no need to wake up soon
continue;
}
LOG(1) << "*** start balancing round. "
<< "waitForDelete: " << balancerConfig->waitForDelete()
<< ", secondaryThrottle: "
<< balancerConfig->getSecondaryThrottle().toBSON();
OCCASIONALLY warnOnMultiVersion(
uassertStatusOK(_clusterStats->getStats(txn.get())));
Status status = _enforceTagRanges(txn.get());
if (!status.isOK()) {
warning() << "Failed to enforce tag ranges" << causedBy(status);
} else {
LOG(1) << "Done enforcing tag range boundaries.";
}
const auto candidateChunks = uassertStatusOK(
_chunkSelectionPolicy->selectChunksToMove(txn.get(), _balancedLastTime));
if (candidateChunks.empty()) {
LOG(1) << "no need to move any chunk";
_balancedLastTime = 0;
} else {
_balancedLastTime = _moveChunks(txn.get(),
candidateChunks,
balancerConfig->getSecondaryThrottle(),
balancerConfig->waitForDelete());
roundDetails.setSucceeded(static_cast<int>(candidateChunks.size()),
_balancedLastTime);
grid.catalogManager(txn.get())
->logAction(txn.get(), "balancer.round", "", roundDetails.toBSON());
}
LOG(1) << "*** End of balancing round";
}
// Ping again so scripts can determine if we're active without waiting
_ping(txn.get(), true);
sleepFor(_balancedLastTime ? kShortBalanceRoundInterval : balanceRoundInterval);
} catch (const std::exception& e) {
log() << "caught exception while doing balance: " << e.what();
// Just to match the opening statement if in log level 1
LOG(1) << "*** End of balancing round";
// This round failed, tell the world!
roundDetails.setFailed(e.what());
grid.catalogManager(txn.get())
->logAction(txn.get(), "balancer.round", "", roundDetails.toBSON());
// Sleep a fair amount before retrying because of the error
sleepFor(balanceRoundInterval);
}
}
}
StatusWith<vector<MigrateInfo>> Balancer::_getCandidateChunks(OperationContext* txn) {
vector<CollectionType> collections;
Status collsStatus =
grid.catalogManager(txn)->getCollections(txn, nullptr, &collections, nullptr);
if (!collsStatus.isOK()) {
return collsStatus;
}
if (collections.empty()) {
return vector<MigrateInfo>();
}
// Get a list of all the shards that are participating in this balance round along with any
// maximum allowed quotas and current utilization. We get the latter by issuing
// db.serverStatus() (mem.mapped) to all shards.
//
// TODO: skip unresponsive shards and mark information as stale.
auto shardInfoStatus = DistributionStatus::populateShardInfoMap(txn);
if (!shardInfoStatus.isOK()) {
return shardInfoStatus.getStatus();
}
const ShardInfoMap shardInfo(std::move(shardInfoStatus.getValue()));
if (shardInfo.size() < 2) {
return vector<MigrateInfo>();
}
OCCASIONALLY warnOnMultiVersion(shardInfo);
std::vector<MigrateInfo> candidateChunks;
// For each collection, check if the balancing policy recommends moving anything around.
for (const auto& coll : collections) {
// Skip collections for which balancing is disabled
const NamespaceString& nss = coll.getNs();
if (!coll.getAllowBalance()) {
LOG(1) << "Not balancing collection " << nss << "; explicitly disabled.";
continue;
}
std::vector<ChunkType> allNsChunks;
Status status = grid.catalogManager(txn)->getChunks(txn,
BSON(ChunkType::ns(nss.ns())),
BSON(ChunkType::min() << 1),
boost::none, // all chunks
&allNsChunks,
nullptr);
if (!status.isOK()) {
warning() << "failed to load chunks for ns " << nss.ns() << causedBy(status);
continue;
}
set<BSONObj> allChunkMinimums;
map<string, vector<ChunkType>> shardToChunksMap;
for (const ChunkType& chunk : allNsChunks) {
allChunkMinimums.insert(chunk.getMin().getOwned());
vector<ChunkType>& chunksList = shardToChunksMap[chunk.getShard()];
chunksList.push_back(chunk);
}
if (shardToChunksMap.empty()) {
LOG(1) << "skipping empty collection (" << nss.ns() << ")";
continue;
}
for (ShardInfoMap::const_iterator i = shardInfo.begin(); i != shardInfo.end(); ++i) {
// This loop just makes sure there is an entry in shardToChunksMap for every shard
shardToChunksMap[i->first];
}
DistributionStatus distStatus(shardInfo, shardToChunksMap);
// TODO: TagRange contains all the information from TagsType except for the namespace,
// so maybe the two can be merged at some point in order to avoid the
// transformation below.
vector<TagRange> ranges;
{
vector<TagsType> collectionTags;
uassertStatusOK(
grid.catalogManager(txn)->getTagsForCollection(txn, nss.ns(), &collectionTags));
for (const auto& tt : collectionTags) {
ranges.push_back(
TagRange(tt.getMinKey().getOwned(), tt.getMaxKey().getOwned(), tt.getTag()));
uassert(16356,
str::stream() << "tag ranges not valid for: " << nss.ns(),
distStatus.addTagRange(ranges.back()));
}
}
auto statusGetDb = grid.catalogCache()->getDatabase(txn, nss.db().toString());
if (!statusGetDb.isOK()) {
warning() << "could not load db config to balance collection [" << nss.ns()
<< "]: " << statusGetDb.getStatus();
continue;
}
shared_ptr<DBConfig> cfg = statusGetDb.getValue();
// This line reloads the chunk manager once if this process doesn't know the collection
// is sharded yet.
shared_ptr<ChunkManager> cm = cfg->getChunkManagerIfExists(txn, nss.ns(), true);
if (!cm) {
warning() << "could not load chunks to balance " << nss.ns() << " collection";
continue;
}
// Loop through tags to make sure no chunk spans tags. Split on tag min for all chunks.
bool didAnySplits = false;
for (const TagRange& range : ranges) {
BSONObj min =
cm->getShardKeyPattern().getKeyPattern().extendRangeBound(range.min, false);
if (allChunkMinimums.count(min) > 0) {
continue;
}
didAnySplits = true;
log() << "nss: " << nss.ns() << " need to split on " << min
<< " because there is a range there";
vector<BSONObj> splitPoints;
splitPoints.push_back(min);
shared_ptr<Chunk> c = cm->findIntersectingChunk(txn, min);
Status status = c->multiSplit(txn, splitPoints, NULL);
if (!status.isOK()) {
error() << "split failed: " << status;
} else {
LOG(1) << "split worked";
}
break;
}
if (didAnySplits) {
// State change, just wait till next round
continue;
}
shared_ptr<MigrateInfo> migrateInfo(
BalancerPolicy::balance(nss.ns(), distStatus, _balancedLastTime));
if (migrateInfo) {
candidateChunks.emplace_back(*migrateInfo);
}
}
return candidateChunks;
}
void Balancer::_doBalanceRound( DBClientBase& conn, vector<CandidateChunkPtr>* candidateChunks ) {
verify( candidateChunks );
//
// 1. Check whether there is any sharded collection to be balanced by querying
// the ShardsNS::collections collection
//
auto_ptr<DBClientCursor> cursor = conn.query(CollectionType::ConfigNS, BSONObj());
if ( NULL == cursor.get() ) {
warning() << "could not query " << CollectionType::ConfigNS
<< " while trying to balance" << endl;
return;
}
vector< string > collections;
while ( cursor->more() ) {
BSONObj col = cursor->nextSafe();
// sharded collections will have a shard "key".
if ( ! col[CollectionType::keyPattern()].eoo() &&
! col[CollectionType::noBalance()].trueValue() ){
collections.push_back( col[CollectionType::ns()].String() );
}
else if( col[CollectionType::noBalance()].trueValue() ){
LOG(1) << "not balancing collection " << col[CollectionType::ns()].String()
<< ", explicitly disabled" << endl;
}
}
cursor.reset();
if ( collections.empty() ) {
LOG(1) << "no collections to balance" << endl;
return;
}
//
// 2. Get a list of all the shards that are participating in this balance round
// along with any maximum allowed quotas and current utilization. We get the
// latter by issuing db.serverStatus() (mem.mapped) to all shards.
//
// TODO: skip unresponsive shards and mark information as stale.
//
ShardInfoMap shardInfo;
Status loadStatus = DistributionStatus::populateShardInfoMap(&shardInfo);
if (!loadStatus.isOK()) {
warning() << "failed to load shard metadata" << causedBy(loadStatus) << endl;
return;
}
if (shardInfo.size() < 2) {
LOG(1) << "can't balance without more active shards" << endl;
return;
}
OCCASIONALLY warnOnMultiVersion( shardInfo );
//
// 3. For each collection, check if the balancing policy recommends moving anything around.
//
for (vector<string>::const_iterator it = collections.begin(); it != collections.end(); ++it ) {
const string& ns = *it;
OwnedPointerMap<string, OwnedPointerVector<ChunkType> > shardToChunksMap;
cursor = conn.query(ChunkType::ConfigNS,
QUERY(ChunkType::ns(ns)).sort(ChunkType::min()));
set<BSONObj> allChunkMinimums;
while ( cursor->more() ) {
BSONObj chunkDoc = cursor->nextSafe().getOwned();
auto_ptr<ChunkType> chunk(new ChunkType());
string errmsg;
if (!chunk->parseBSON(chunkDoc, &errmsg)) {
error() << "bad chunk format for " << chunkDoc
<< ": " << errmsg << endl;
return;
}
allChunkMinimums.insert(chunk->getMin().getOwned());
OwnedPointerVector<ChunkType>*& chunkList =
shardToChunksMap.mutableMap()[chunk->getShard()];
if (chunkList == NULL) {
chunkList = new OwnedPointerVector<ChunkType>();
}
chunkList->mutableVector().push_back(chunk.release());
}
cursor.reset();
if (shardToChunksMap.map().empty()) {
LOG(1) << "skipping empty collection (" << ns << ")";
continue;
}
for (ShardInfoMap::const_iterator i = shardInfo.begin(); i != shardInfo.end(); ++i) {
// this just makes sure there is an entry in shardToChunksMap for every shard
OwnedPointerVector<ChunkType>*& chunkList =
shardToChunksMap.mutableMap()[i->first];
if (chunkList == NULL) {
chunkList = new OwnedPointerVector<ChunkType>();
}
}
DistributionStatus status(shardInfo, shardToChunksMap.map());
// load tags
Status result = clusterCreateIndex(TagsType::ConfigNS,
BSON(TagsType::ns() << 1 << TagsType::min() << 1),
true, // unique
WriteConcernOptions::AllConfigs,
NULL);
if ( !result.isOK() ) {
warning() << "could not create index tags_1_min_1: " << result.reason() << endl;
continue;
}
cursor = conn.query(TagsType::ConfigNS,
QUERY(TagsType::ns(ns)).sort(TagsType::min()));
vector<TagRange> ranges;
while ( cursor->more() ) {
BSONObj tag = cursor->nextSafe();
TagRange tr(tag[TagsType::min()].Obj().getOwned(),
tag[TagsType::max()].Obj().getOwned(),
tag[TagsType::tag()].String());
ranges.push_back(tr);
uassert(16356,
str::stream() << "tag ranges not valid for: " << ns,
status.addTagRange(tr) );
}
cursor.reset();
DBConfigPtr cfg = grid.getDBConfig( ns );
if ( !cfg ) {
warning() << "could not load db config to balance " << ns << " collection" << endl;
continue;
}
// This line reloads the chunk manager once if this process doesn't know the collection
// is sharded yet.
ChunkManagerPtr cm = cfg->getChunkManagerIfExists( ns, true );
if ( !cm ) {
warning() << "could not load chunks to balance " << ns << " collection" << endl;
continue;
}
// loop through tags to make sure no chunk spans tags; splits on tag min. for all chunks
bool didAnySplits = false;
for ( unsigned i = 0; i < ranges.size(); i++ ) {
BSONObj min = ranges[i].min;
min = cm->getShardKey().extendRangeBound( min, false );
if ( allChunkMinimums.count( min ) > 0 )
continue;
didAnySplits = true;
log() << "ns: " << ns << " need to split on "
<< min << " because there is a range there" << endl;
ChunkPtr c = cm->findIntersectingChunk( min );
vector<BSONObj> splitPoints;
splitPoints.push_back( min );
BSONObj res;
if ( !c->multiSplit( splitPoints, res ) ) {
error() << "split failed: " << res << endl;
}
else {
LOG(1) << "split worked: " << res << endl;
}
break;
}
if ( didAnySplits ) {
// state change, just wait till next round
continue;
}
CandidateChunk* p = _policy->balance( ns, status, _balancedLastTime );
if ( p ) candidateChunks->push_back( CandidateChunkPtr( p ) );
}
}
void Balancer::_doBalanceRound( DBClientBase& conn, vector<CandidateChunkPtr>* candidateChunks ) {
verify( candidateChunks );
//
// 1. Check whether there is any sharded collection to be balanced by querying
// the ShardsNS::collections collection
//
auto_ptr<DBClientCursor> cursor = conn.query(CollectionType::ConfigNS, BSONObj());
vector< string > collections;
while ( cursor->more() ) {
BSONObj col = cursor->nextSafe();
// sharded collections will have a shard "key".
if ( ! col[CollectionType::keyPattern()].eoo() &&
! col[CollectionType::noBalance()].trueValue() ){
collections.push_back( col[CollectionType::ns()].String() );
}
else if( col[CollectionType::noBalance()].trueValue() ){
LOG(1) << "not balancing collection " << col[CollectionType::ns()].String()
<< ", explicitly disabled" << endl;
}
}
cursor.reset();
if ( collections.empty() ) {
LOG(1) << "no collections to balance" << endl;
return;
}
//
// 2. Get a list of all the shards that are participating in this balance round
// along with any maximum allowed quotas and current utilization. We get the
// latter by issuing db.serverStatus() (mem.mapped) to all shards.
//
// TODO: skip unresponsive shards and mark information as stale.
//
vector<Shard> allShards;
Shard::getAllShards( allShards );
if ( allShards.size() < 2) {
LOG(1) << "can't balance without more active shards" << endl;
return;
}
ShardInfoMap shardInfo;
for ( vector<Shard>::const_iterator it = allShards.begin(); it != allShards.end(); ++it ) {
const Shard& s = *it;
ShardStatus status = s.getStatus();
shardInfo[ s.getName() ] = ShardInfo( s.getMaxSize(),
status.mapped(),
s.isDraining(),
status.hasOpsQueued(),
s.tags(),
status.mongoVersion()
);
}
OCCASIONALLY warnOnMultiVersion( shardInfo );
//
// 3. For each collection, check if the balancing policy recommends moving anything around.
//
for (vector<string>::const_iterator it = collections.begin(); it != collections.end(); ++it ) {
const string& ns = *it;
map< string,vector<BSONObj> > shardToChunksMap;
cursor = conn.query(ChunkType::ConfigNS,
QUERY(ChunkType::ns(ns)).sort(ChunkType::min()));
set<BSONObj> allChunkMinimums;
while ( cursor->more() ) {
BSONObj chunk = cursor->nextSafe().getOwned();
vector<BSONObj>& chunks = shardToChunksMap[chunk[ChunkType::shard()].String()];
allChunkMinimums.insert( chunk[ChunkType::min()].Obj() );
chunks.push_back( chunk );
}
cursor.reset();
if (shardToChunksMap.empty()) {
LOG(1) << "skipping empty collection (" << ns << ")";
continue;
}
for ( vector<Shard>::iterator i=allShards.begin(); i!=allShards.end(); ++i ) {
// this just makes sure there is an entry in shardToChunksMap for every shard
Shard s = *i;
shardToChunksMap[s.getName()].size();
}
DistributionStatus status( shardInfo, shardToChunksMap );
// load tags
conn.ensureIndex(TagsType::ConfigNS,
BSON(TagsType::ns() << 1 << TagsType::min() << 1),
true);
cursor = conn.query(TagsType::ConfigNS,
QUERY(TagsType::ns(ns)).sort(TagsType::min()));
vector<TagRange> ranges;
while ( cursor->more() ) {
BSONObj tag = cursor->nextSafe();
TagRange tr(tag[TagsType::min()].Obj().getOwned(),
tag[TagsType::max()].Obj().getOwned(),
tag[TagsType::tag()].String());
ranges.push_back(tr);
uassert(16356,
str::stream() << "tag ranges not valid for: " << ns,
status.addTagRange(tr) );
}
cursor.reset();
DBConfigPtr cfg = grid.getDBConfig( ns );
if ( !cfg ) {
warning() << "could not load db config to balance " << ns << " collection" << endl;
continue;
}
// This line reloads the chunk manager once if this process doesn't know the collection
// is sharded yet.
ChunkManagerPtr cm = cfg->getChunkManagerIfExists( ns, true );
if ( !cm ) {
warning() << "could not load chunks to balance " << ns << " collection" << endl;
continue;
}
// loop through tags to make sure no chunk spans tags; splits on tag min. for all chunks
bool didAnySplits = false;
for ( unsigned i = 0; i < ranges.size(); i++ ) {
BSONObj min = ranges[i].min;
min = cm->getShardKey().extendRangeBound( min, false );
if ( allChunkMinimums.count( min ) > 0 )
continue;
didAnySplits = true;
log() << "ns: " << ns << " need to split on "
<< min << " because there is a range there" << endl;
ChunkPtr c = cm->findIntersectingChunk( min );
vector<BSONObj> splitPoints;
splitPoints.push_back( min );
BSONObj res;
if ( !c->multiSplit( splitPoints, res ) ) {
error() << "split failed: " << res << endl;
}
else {
LOG(1) << "split worked: " << res << endl;
}
break;
}
if ( didAnySplits ) {
// state change, just wait till next round
continue;
}
CandidateChunk* p = _policy->balance( ns, status, _balancedLastTime );
if ( p ) candidateChunks->push_back( CandidateChunkPtr( p ) );
}
}
