Question

我们刚刚从dbcp迁移到tomcat jdbc连接池。我们在加载时尝试了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)

请注意：

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

哪些连接不忙？忙碌的数字在此之后继续下降，但我们仍然无法建立联系。

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"/>

env：ubuntu和tomcat 6. db - mysql

Answer 1

看一下ConnectionPool.java的来源，您似乎在borrowConnection()方法中点击了此代码段：

        //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;
            }
        }

因此，根据此，您的连接是 Null 。

在行上检索con的值：

PooledConnection con = idle.poll();

如果您跟踪代码，您会看到idle（取决于您的配置，但默认情况下）FairBlockingQueue。您可以查看提示的实现。

通常，您必须关闭ResultSet，Statements和Connections，并且已使用的连接应正确释放回池中。不正确这样做可能导致连接从未被关闭=＆gt;永远不再可用于重用（连接池“泄漏”）。

我建议你构建一些关于池状态的详细日志记录并监视它以隔离问题。

Apache的一些准则，用于防止数据库连接池泄漏：

removeAbandoned="true"

已删除并回收废弃的数据库连接

removeAbandonedTimeout="60"

设置数据库连接在被视为放弃之前处于空闲状态的秒数

logAbandoned="true"

记录放弃数据库连接资源的代码的堆栈跟踪。请记住，“记录已放弃的Connections会增加每个连接借用的开销，因为必须生成堆栈跟踪。”

我仍然认为稍微增加maxWait值（1200,1500,1700 - 只是实验，从用户的角度来看，响应时间没有差别）将清除那些罕见的情况，在这些情况下你仍然会遇到问题

Answer 2

“哪些连接不忙？”

听起来他们已被删除，并且出于某种原因，您的连接池并未尝试重新连接它们。

将此添加到您要连接的网址：

autoReconnect=true

将此属性添加到资源中会导致死连接自动重新连接。

validationQuery="SELECT 1"

此外，这应该允许您查看被删除的连接：

logAbandoned="true"

堆栈溢出有多个类似的问题。

Tomcat connection pooling,idle connections,and connection creation JDBC Connection pool not reopening Connections in tomcat

然而，也可能是你没有完全释放连接，这是他们死亡的原因。 JDBC MySql connection pooling practices to avoid exhausted connection pool

Answer 3

似乎是池中的错误，size变量递增，然后尝试创建连接，但如果创建失败......我们的size值很大，而且池中没有实际连接 - 可怕：

    //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

缺少tomcat jdbc连接池中的连接

3 个答案: