mongodb连接池参数备忘

• connectionsPerHost：每个主机的连接数
• threadsAllowedToBlockForConnectionMultiplier：线程队列数，它以上面 connectionsPerHost值相乘的结果就是线程队列最大值。如果连接线程排满了队列就会抛出“Out of semaphores to get db”错误。
• maxWaitTime:最大等待连接的线程阻塞时间
• connectTimeout：连接超时的毫秒。0是默认和无限
• socketTimeout：socket超时。0是默认和无限
• autoConnectRetry：这个控制是否在一个连接时，系统会自动重试

MongoOptions opt = mongo.getMongoOptions();
opt.connectionsPerHost = 10 ; //poolsize
opt.threadsAllowedToBlockForConnectionMultiplier = 10 ;
//其他参数类似

Field Summary

boolean	autoConnectRetry             If true, the driver will keep trying to connect to the same server in case that the socket cannot be established.
int	connectionsPerHost             The maximum number of connections allowed per host for this Mongo instance.
int	connectTimeout             The connection timeout in milliseconds.
DBDecoderFactory	dbDecoderFactory             Override the DBCallback factory.
DBEncoderFactory	dbEncoderFactory             Override the encoding factory.
String	description             The description for Mongo  instances created with these options.
boolean	fsync             The "fsync" value of the global WriteConcern.
boolean	j             The "j" value of the global WriteConcern.
long	maxAutoConnectRetryTime             The maximum amount of time in MS to spend retrying to open connection to the same server.
int	maxWaitTime             The maximum wait time in ms that a thread may wait for a connection to become available.
boolean	safe             If true  the driver will use a WriteConcern of WriteConcern.SAFE for all operations.
boolean	slaveOk             Deprecated.  Replaced in MongoDB 2.0/Java Driver 2.7 with ReadPreference.SECONDARY
SocketFactory	socketFactory             sets the socket factory for creating sockets to mongod Default is SocketFactory.getDefault()
boolean	socketKeepAlive             This flag controls the socket keep alive feature that keeps a connection alive through firewalls Socket.setKeepAlive(boolean)  Default is false.
int	socketTimeout             The socket timeout in milliseconds It is used for I/O socket read and write operations Socket.setSoTimeout(int)  Default is 0 and means no timeout.
int	threadsAllowedToBlockForConnectionMultiplier             this multiplier, multiplied with the connectionsPerHost setting, gives the maximum number of threads that may be waiting for a connection to become available from the pool.
int	w             The "w" value of the global WriteConcern.
int	wtimeout             The "wtimeout" value of the global WriteConcern.