bool mergeChunks( OperationContext* txn,
const NamespaceString& nss,
const BSONObj& minKey,
const BSONObj& maxKey,
const OID& epoch,
string* errMsg ) {
//
// Get sharding state up-to-date
//
ConnectionString configLoc = ConnectionString::parse( shardingState.getConfigServer(),
*errMsg );
if ( !configLoc.isValid() ){
warning() << *errMsg << endl;
return false;
}
//
// Get the distributed lock
//
ScopedDistributedLock collLock( configLoc, nss.ns() );
collLock.setLockMessage( stream() << "merging chunks in " << nss.ns() << " from "
<< minKey << " to " << maxKey );
Status acquisitionStatus = collLock.tryAcquire();
if (!acquisitionStatus.isOK()) {
*errMsg = stream() << "could not acquire collection lock for " << nss.ns()
<< " to merge chunks in [" << minKey << "," << maxKey << ")"
<< causedBy(acquisitionStatus);
warning() << *errMsg << endl;
return false;
}
//
// We now have the collection lock, refresh metadata to latest version and sanity check
//
ChunkVersion shardVersion;
Status status = shardingState.refreshMetadataNow(txn, nss.ns(), &shardVersion);
if ( !status.isOK() ) {
*errMsg = str::stream() << "could not merge chunks, failed to refresh metadata for "
<< nss.ns() << causedBy( status.reason() );
warning() << *errMsg << endl;
return false;
}
if ( epoch.isSet() && shardVersion.epoch() != epoch ) {
*errMsg = stream() << "could not merge chunks, collection " << nss.ns()
<< " has changed" << " since merge was sent" << "(sent epoch : "
<< epoch.toString()
<< ", current epoch : " << shardVersion.epoch().toString() << ")";
warning() << *errMsg << endl;
return false;
}
CollectionMetadataPtr metadata = shardingState.getCollectionMetadata( nss.ns() );
if ( !metadata || metadata->getKeyPattern().isEmpty() ) {
*errMsg = stream() << "could not merge chunks, collection " << nss.ns()
<< " is not sharded";
warning() << *errMsg << endl;
return false;
}
dassert( metadata->getShardVersion().equals( shardVersion ) );
if ( !metadata->isValidKey( minKey ) || !metadata->isValidKey( maxKey ) ) {
*errMsg = stream() << "could not merge chunks, the range "
<< rangeToString( minKey, maxKey ) << " is not valid"
<< " for collection " << nss.ns() << " with key pattern "
<< metadata->getKeyPattern();
warning() << *errMsg << endl;
return false;
}
//
// Get merged chunk information
//
ChunkVersion mergeVersion = metadata->getCollVersion();
mergeVersion.incMinor();
OwnedPointerVector<ChunkType> chunksToMerge;
ChunkType itChunk;
itChunk.setMin( minKey );
itChunk.setMax( minKey );
itChunk.setNS( nss.ns() );
itChunk.setShard( shardingState.getShardName() );
while ( itChunk.getMax().woCompare( maxKey ) < 0 &&
metadata->getNextChunk( itChunk.getMax(), &itChunk ) ) {
auto_ptr<ChunkType> saved( new ChunkType );
itChunk.cloneTo( saved.get() );
chunksToMerge.mutableVector().push_back( saved.release() );
}
if ( chunksToMerge.empty() ) {
*errMsg = stream() << "could not merge chunks, collection " << nss.ns()
<< " range starting at " << minKey
<< " and ending at " << maxKey
<< " does not belong to shard " << shardingState.getShardName();
warning() << *errMsg << endl;
return false;
}
//
// Validate the range starts and ends at chunks and has no holes, error if not valid
//
BSONObj firstDocMin = ( *chunksToMerge.begin() )->getMin();
BSONObj firstDocMax = ( *chunksToMerge.begin() )->getMax();
// minKey is inclusive
bool minKeyInRange = rangeContains( firstDocMin, firstDocMax, minKey );
if ( !minKeyInRange ) {
*errMsg = stream() << "could not merge chunks, collection " << nss.ns()
<< " range starting at " << minKey
<< " does not belong to shard " << shardingState.getShardName();
warning() << *errMsg << endl;
return false;
}
BSONObj lastDocMin = ( *chunksToMerge.rbegin() )->getMin();
BSONObj lastDocMax = ( *chunksToMerge.rbegin() )->getMax();
// maxKey is exclusive
bool maxKeyInRange = lastDocMin.woCompare( maxKey ) < 0 &&
lastDocMax.woCompare( maxKey ) >= 0;
if ( !maxKeyInRange ) {
*errMsg = stream() << "could not merge chunks, collection " << nss.ns()
<< " range ending at " << maxKey
<< " does not belong to shard " << shardingState.getShardName();
warning() << *errMsg << endl;
return false;
}
bool validRangeStartKey = firstDocMin.woCompare( minKey ) == 0;
bool validRangeEndKey = lastDocMax.woCompare( maxKey ) == 0;
if ( !validRangeStartKey || !validRangeEndKey ) {
*errMsg = stream() << "could not merge chunks, collection " << nss.ns()
<< " does not contain a chunk "
<< ( !validRangeStartKey ? "starting at " + minKey.toString() : "" )
<< ( !validRangeStartKey && !validRangeEndKey ? " or " : "" )
<< ( !validRangeEndKey ? "ending at " + maxKey.toString() : "" );
warning() << *errMsg << endl;
return false;
}
if ( chunksToMerge.size() == 1 ) {
*errMsg = stream() << "could not merge chunks, collection " << nss.ns()
<< " already contains chunk for " << rangeToString( minKey, maxKey );
warning() << *errMsg << endl;
return false;
}
bool holeInRange = false;
// Look for hole in range
ChunkType* prevChunk = *chunksToMerge.begin();
ChunkType* nextChunk = NULL;
for ( OwnedPointerVector<ChunkType>::const_iterator it = chunksToMerge.begin();
it != chunksToMerge.end(); ++it ) {
if ( it == chunksToMerge.begin() ) continue;
nextChunk = *it;
if ( prevChunk->getMax().woCompare( nextChunk->getMin() ) != 0 ) {
holeInRange = true;
break;
}
prevChunk = nextChunk;
}
if ( holeInRange ) {
dassert( NULL != nextChunk );
*errMsg = stream() << "could not merge chunks, collection " << nss.ns()
<< " has a hole in the range " << rangeToString( minKey, maxKey )
<< " at " << rangeToString( prevChunk->getMax(),
nextChunk->getMin() );
warning() << *errMsg << endl;
return false;
}
//
// Run apply ops command
//
BSONObj applyOpsCmd = buildApplyOpsCmd( chunksToMerge,
shardVersion,
mergeVersion );
bool ok;
BSONObj result;
try {
ScopedDbConnection conn( configLoc, 30.0 );
ok = conn->runCommand( "config", applyOpsCmd, result );
if ( !ok ) *errMsg = result.toString();
conn.done();
}
catch( const DBException& ex ) {
ok = false;
*errMsg = ex.toString();
}
if ( !ok ) {
*errMsg = stream() << "could not merge chunks for " << nss.ns()
<< ", writing to config failed" << causedBy( errMsg );
warning() << *errMsg << endl;
return false;
}
//
// Install merged chunk metadata
//
{
Lock::DBLock writeLk(txn->lockState(), nss.db(), newlm::MODE_X);
shardingState.mergeChunks(txn, nss.ns(), minKey, maxKey, mergeVersion);
}
//
// Log change
//
BSONObj mergeLogEntry = buildMergeLogEntry( chunksToMerge,
shardVersion,
mergeVersion );
configServer.logChange( "merge", nss.ns(), mergeLogEntry );
return true;
}
