java - hibernate - 频繁查询时出错

Question

我使用服务器 Tomcat + HttpServlet + hibernate。我测试了服务器性能，为此，我创建了一个应用程序来模拟 500 个客户端的操作，每个客户端都定期向服务器重复 HTTP 请求。

当请求连接 = 900 (+-100) 时，我开始出现 hibernate 错误

24.04.2013 12:27:20 org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 0, SQLState: 08001
24.04.2013 12:27:23 org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
org.hibernate.exception.JDBCConnectionException: Could not open connection
    at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:131)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:304)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:169)
    at org.hibernate.engine.jdbc.internal.proxy.ConnectionProxyHandler.extractPhysicalConnection(ConnectionProxyHandler.java:82)
    at org.hibernate.engine.jdbc.internal.proxy.ConnectionProxyHandler.continueInvocation(ConnectionProxyHandler.java:138)
    at org.hibernate.engine.jdbc.internal.proxy.AbstractProxyHandler.invoke(AbstractProxyHandler.java:81)
    at $Proxy24.prepareStatement(Unknown Source)
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$5.doPrepare(StatementPreparerImpl.java:147)
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:166)
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.prepareQueryStatement(StatementPreparerImpl.java:145)
    at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1711)
    at org.hibernate.loader.Loader.doQuery(Loader.java:828)
    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:289)
    at org.hibernate.loader.Loader.doList(Loader.java:2438)
    at org.hibernate.loader.Loader.doList(Loader.java:2424)
    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2254)
    at org.hibernate.loader.Loader.list(Loader.java:2249)
    at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:470)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:355)
    at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:195)
    at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1248)
    at org.hibernate.internal.QueryImpl.list(QueryImpl.java:101)
    at org.hibernate.internal.AbstractQueryImpl.uniqueResult(AbstractQueryImpl.java:890)
    at actions.player.LoginAction.perform(LoginAction.java:20)
    at action.Action.performAction(Action.java:66)
    at servlets.RequestHandlerServlet.service(RequestHandlerServlet.java:34)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: org.postgresql.util.PSQLException:
org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:136)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:64)
    at org.postgresql.jdbc2.AbstractJdbc2Connection.<init>(AbstractJdbc2Connection.java:123)
    at org.postgresql.jdbc3.AbstractJdbc3Connection.<init>(AbstractJdbc3Connection.java:28)
    at org.postgresql.jdbc3g.AbstractJdbc3gConnection.<init>(AbstractJdbc3gConnection.java:20)
    at org.postgresql.jdbc4.AbstractJdbc4Connection.<init>(AbstractJdbc4Connection.java:30)
    at org.postgresql.jdbc4.Jdbc4Connection.<init>(Jdbc4Connection.java:22)
    at org.postgresql.Driver.makeConnection(Driver.java:391)
    at org.postgresql.Driver.connect(Driver.java:265)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl.getConnection(DriverManagerConnectionProviderImpl.java:193)
    at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:281)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:297)
    ... 41 more
Caused by: java.net.ConnectException: Connection refused: connect
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(Unknown Source)
    at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.SocksSocketImpl.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at org.postgresql.core.PGStream.<init>(PGStream.java:60)
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:74)
    ... 54 more
org.hibernate.exception.JDBCConnectionException: Could not open connection
    at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:131)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:304)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:169)
    at org.hibernate.engine.jdbc.internal.proxy.ConnectionProxyHandler.extractPhysicalConnection(ConnectionProxyHandler.java:82)

请帮忙，任何想法...

Answer 1

具体问题是:

Caused by: java.net.ConnectException: Connection refused: connect

这表明，当 PgJDBC 尝试打开到 PostgreSQL 服务器的 TCP/IP 套接字时，连接被拒绝了。

当 PostgreSQL 服务器过载时，这不会发生；相反，它会接受连接足够长的时间来回复错误，提及“太多连接”或“max_connections”。当我针对 Pg 9.3-HEAD 使用 psql 进行测试时，我得到:

FATAL:  sorry, too many clients already

同样，如果身份验证有问题，PostgreSQL 将接受连接，回复错误消息并关闭连接，如:

FATAL:  no pg_hba.conf entry for host "[local]", user "craig", database "postgres"

或:

FATAL:  password authentication failed for user "craig"

您看到的是操作系统或网络堆栈中的较低级别问题。它发生在 PostgreSQL 有机会接受连接之前。由于您没有提到您的操作系统，无论 Pg 服务器是本地的还是远程的应用程序服务器，或者几乎任何其他东西，都很难进一步提供帮助。我将从以下方面开始:

• 检查 PostgreSQL 日志中有关 accept() 的错误或任何其他看起来异常的错误
• 调查操作系统中的任何 TCP/IP 连接限制和最大打开文件限制
• 确保我没有使用任何类型的狡猾的第 3 方软件防火墙或“互联网安全”套件

此外，您应该研究使用连接池 - 应用内连接池或外部池(如 PgPool-II)，使您可以将 max_connections 减少到有效水平。 PostgreSQL 将在更少 连接的情况下执行更好；理想的数量取决于工作负载和硬件。参见 PostgreSQL wiki: Number of database connections .