diff options
Diffstat (limited to 's/d_state.cpp')
| -rw-r--r-- | s/d_state.cpp | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/s/d_state.cpp b/s/d_state.cpp index 929d2a8..638d8c1 100644 --- a/s/d_state.cpp +++ b/s/d_state.cpp @@ -45,7 +45,8 @@ namespace mongo { // -----ShardingState START ---- ShardingState::ShardingState() - : _enabled(false) , _mutex( "ShardingState" ) { + : _enabled(false) , _mutex( "ShardingState" ), + _configServerTickets( 3 /* max number of concurrent config server refresh threads */ ) { } void ShardingState::enable( const string& server ) { @@ -183,7 +184,23 @@ namespace mongo { bool ShardingState::trySetVersion( const string& ns , ConfigVersion& version /* IN-OUT */ ) { - // fast path - requested version is at the same version as this chunk manager + // Currently this function is called after a getVersion(), which is the first "check", and the assumption here + // is that we don't do anything nearly as long as a remote query in a thread between then and now. + // Otherwise it may be worth adding an additional check without the _configServerMutex below, since then it + // would be likely that the version may have changed in the meantime without waiting for or fetching config results. + + // TODO: Mutex-per-namespace? + + LOG( 2 ) << "trying to set shard version of " << version.toString() << " for '" << ns << "'" << endl; + + _configServerTickets.waitForTicket(); + TicketHolderReleaser needTicketFrom( &_configServerTickets ); + + // fast path - double-check if requested version is at the same version as this chunk manager before verifying + // against config server + // + // This path will short-circuit the version set if another thread already managed to update the version in the + // meantime. First check is from getVersion(). // // cases: // + this shard updated the version for a migrate's commit (FROM side) @@ -191,12 +208,15 @@ namespace mongo { // + two clients reloaded // one triggered the 'slow path' (below) // when the second's request gets here, the version is already current + ConfigVersion storedVersion; { scoped_lock lk( _mutex ); ChunkManagersMap::const_iterator it = _chunks.find( ns ); - if ( it != _chunks.end() && it->second->getVersion() == version ) + if ( it != _chunks.end() && ( storedVersion = it->second->getVersion() ) == version ) return true; } + + LOG( 2 ) << "verifying cached version " << storedVersion.toString() << " and new version " << version.toString() << " for '" << ns << "'" << endl; // slow path - requested version is different than the current chunk manager's, if one exists, so must check for // newest version in the config server @@ -209,8 +229,10 @@ namespace mongo { // the secondary had no state (managers) at all, so every client request will fall here // + a stale client request a version that's not current anymore + // Can't lock default mutex while creating ShardChunkManager, b/c may have to create a new connection to myself const string c = (_configServer == _shardHost) ? "" /* local */ : _configServer; ShardChunkManagerPtr p( new ShardChunkManager( c , ns , _shardName ) ); + { scoped_lock lk( _mutex ); |