Vertica修改最大并发连接数

本文地址：http://blog.csdn.net/kongxx/article/details/7176961

最近在对Vertica做压力测试的时候，发现当并发请求数达到50+的时候就会出现下面的异常

com.vertica.util.PSQLException: FATAL: New session rejected due to limit, already 55 sessions active
	at com.vertica.core.v3.ConnectionFactoryImpl.readStartupMessages(Unknown Source)
	at com.vertica.core.v3.ConnectionFactoryImpl.openConnectionImpl(Unknown Source)
	at com.vertica.core.ConnectionFactory.openConnection(Unknown Source)
	at com.vertica.jdbc2.AbstractJdbc2Connection.<init>(Unknown Source)
	at com.vertica.jdbc3.AbstractJdbc3Connection.<init>(Unknown Source)
	at com.vertica.jdbc3g.Jdbc3gConnection.<init>(Unknown Source)
	at com.vertica.Driver.makeConnection(Unknown Source)
	at com.vertica.Driver.connect(Unknown Source)
	at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
	at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582)
	at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:1181)
	at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:106)
	at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
	at DBUtil.getConnection(DBUtil.java:64)
	at DBQueryPerformanceTest.query(DBQueryPerformanceTest.java:46)
	at DBQueryPerformanceTest.access$000(DBQueryPerformanceTest.java:14)
	at DBQueryPerformanceTest$1.execute(DBQueryPerformanceTest.java:40)
	at DBPerformanceTest.runIt(DBPerformanceTest.java:97)
	at DBPerformanceTest$1.run(DBPerformanceTest.java:51)
	at java.lang.Thread.run(Thread.java:619)
com.vertica.util.PSQLException: The connection attempt failed.
	at com.vertica.core.v3.ConnectionFactoryImpl.openConnectionImpl(Unknown Source)
	at com.vertica.core.ConnectionFactory.openConnection(Unknown Source)
	at com.vertica.jdbc2.AbstractJdbc2Connection.<init>(Unknown Source)
	at com.vertica.jdbc3.AbstractJdbc3Connection.<init>(Unknown Source)
	at com.vertica.jdbc3g.Jdbc3gConnection.<init>(Unknown Source)
	at com.vertica.Driver.makeConnection(Unknown Source)
	at com.vertica.Driver.connect(Unknown Source)
	at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
	at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582)
	at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:1181)
	at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:106)
	at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
	at DBUtil.getConnection(DBUtil.java:64)
	at DBQueryPerformanceTest.query(DBQueryPerformanceTest.java:46)
	at DBQueryPerformanceTest.access$000(DBQueryPerformanceTest.java:14)
	at DBQueryPerformanceTest$1.execute(DBQueryPerformanceTest.java:40)
	at DBPerformanceTest.runIt(DBPerformanceTest.java:97)
	at DBPerformanceTest$1.run(DBPerformanceTest.java:51)
	at java.lang.Thread.run(Thread.java:619)
Caused by: java.net.SocketException: Connection reset
	at java.net.SocketInputStream.read(SocketInputStream.java:168)
	at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
	at java.io.BufferedInputStream.read(BufferedInputStream.java:237)
	at com.vertica.core.PGStream.ReceiveChar(Unknown Source)
	at com.vertica.core.v3.ConnectionFactoryImpl.doAuthentication(Unknown Source)
	... 19 more

出现这个问题是由于Vertica中指定了MaxClientSessions参数，此时可以通过下面的SQL来修改此值

SELECT SET_CONFIG_PARAMETER ('MaxClientSessions', 250);