tomcat jdbc 连接池中缺少连接

Posted 2023-02-24

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【中文标题】tomcat jdbc 连接池中缺少连接【英文标题】：Missing connections in tomcat jdbc connection pool 【发布时间】：2012-07-12 03:41:43 【问题描述】：

我们刚刚从 dbcp 迁移到 tomcat jdbc 连接池。我们尝试加载系统并收到以下异常：

java.sql.SQLException: [IA1856] Timeout: Pool empty. Unable to fetch a connection in 1 seconds, none available[size:125; busy:90; idle:0; lastwait:1000].
        at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:632)
        at org.apache.tomcat.jdbc.pool.ConnectionPool.getConnection(ConnectionPool.java:174)
        at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:124)
        at com.inneractive.model.mappings.BasicPersistenceEntityMapping.getConnection(BasicPersistenceEntityMapping.java:233)
        at com.inneractive.model.mappings.BasicPersistenceEntityMapping.callWithConnection(BasicPersistenceEntityMapping.java:243)
        at com.inneractive.model.mappings.PersistenceEntityMapping.get(PersistenceEntityMapping.java:194)
        at com.inneractive.model.data.client.ClientUtils.GetClientByExamples(ClientUtils.java:353)
        at com.inneractive.client.ExternalAdRingsClientStart.getClientInfoByRequestParametersOrInsert(ExternalAdRingsClientStart.java:1329)
        at com.inneractive.client.ExternalAdRingsClientStart.newClientSession(ExternalAdRingsClientStart.java:245)
        at com.inneractive.simpleM2M.web.SimpleM2MProtocolBean.generateCampaign(SimpleM2MProtocolBean.java:235)
        at com.inneractive.simpleM2M.web.SimpleM2MProtocolBean.generateCampaign(SimpleM2MProtocolBean.java:219)
        at com.inneractive.simpleM2M.web.AdsServlet.doGet(AdsServlet.java:175)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:555)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:396)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:662)

注意这一点：

[size:125; busy:90; idle:0; lastwait:1000]

不忙的连接在哪里？在这之后忙碌的号码一直在下降，但我们仍然没有设法获得任何联系。

有什么想法吗？

配置：

<Resource auth="Container" driverClassName="com.mysql.jdbc.Driver"
                factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" loginTimeout="10000"
                maxActive="35" maxIdle="35" maxWait="1000" name="jdbc/mysql"
                password="-----" testOnBorrow="true" testOnReturn="false" type="javax.sql.DataSource"
                url="jdbc:mysql://localhost:3306/my_db?elideSetAutoCommits=true&amp;useDynamicCharsetInfo=false&amp;rewriteBatchedStatements=true&amp;useLocalSessionState=true&amp;useLocalTransactionState=true&amp;alwaysSendSetIsolation=false&amp;cacheServerConfiguration=true&amp;noAccessToProcedureBodies=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"
                username="root" validationQuery="SELECT 1"/>

环境：ubuntu 和 tomcat 6.db - mysql

【问题讨论】：

您是否尝试增加连接池大小？如果增加尺寸会怎样？我无法增加连接数，因为我有多个服务器，而且我处于数据库的上限。但是，我认为这将发生在更大的数量上.. 我们可以猜测，或者您可以发布您的配置。 @ChristopherSchultz 这听起来像是 JDBC/Tomcat 错误，配置中的什么可能导致这样的事情？也许它没有释放回池的连接。尝试监控 mysql 端的连接，使用链接：devdaily.com/blog/post/mysql/… 还将你的 maxWait 增加到至少 10000（默认值是 30000，可能是有原因的） 【参考方案1】：

似乎是池中的一个错误，size变量递增，然后尝试创建连接，但是如果创建失败......我们有 size 值很大并且池中没有实际连接 - 太糟糕了：

    //if we get here, see if we need to create one
    //this is not 100% accurate since it doesn't use a shared
    //atomic variable - a connection can become idle while we are creating
    //a new connection
    if (size.get() < getPoolProperties().getMaxActive()) 
        //atomic duplicate check
        if (size.addAndGet(1) > getPoolProperties().getMaxActive()) 
            //if we got here, two threads passed through the first if
            size.decrementAndGet();
         else 
            //create a connection, we're below the limit
            return createConnection(now, con, username, password);
        
     //end if

【讨论】：

如果创建失败，size 在 createConnection() 中递减，所以它似乎正确，但是我怀疑某些竞争条件会导致 size 的错误值因为我得到了PoolExhaustedException 和size=10, busy=0, idle=0（池是空的，所以它应该尝试创建一个新连接而不是等待一个空闲的连接，但它认为它不是空的，因为大小值）。【参考方案2】：

看一下ConnectionPool.java的来源，你似乎在borrowConnection()方法中打了这段代码sn-p：

        //we didn't get a connection, lets see if we timed out
        if (con == null) 
            if ((System.currentTimeMillis() - now) >= maxWait) 
                throw new SQLException("[" + Thread.currentThread().getName()+"] " +
                    "Timeout: Pool empty. Unable to fetch a connection in " + (maxWait / 1000) +
                    " seconds, none available["+busy.size()+" in use].");
             else 
                //no timeout, lets try again
                continue;

所以根据这个，你的连接是Null。

取到con的值就行了：