ActiveMQ消息队列过多导致客户端连接失败

一、异常描述

jvm 1    | Exception in thread "ActiveMQ BrokerService[localhost] Task-997" java.lang.OutOfMemoryError: unable to create new native thread
jvm 1    |      at java.lang.Thread.start0(Native Method)
jvm 1    |      at java.lang.Thread.start(Unknown Source)
jvm 1    |      at org.apache.activemq.thread.DedicatedTaskRunner.<init>(DedicatedTaskRunner.java:51)
jvm 1    |      at org.apache.activemq.thread.TaskRunnerFactory.createTaskRunner(TaskRunnerFactory.java:140)
jvm 1    |      at org.apache.activemq.broker.TransportConnection.start(TransportConnection.java:1067)
jvm 1    |      at org.apache.activemq.broker.TransportConnector$1$1.run(TransportConnector.java:218)
jvm 1    |      at java.lang.Thread.run(Unknown Source)

或

jvm 1    | ERROR | Could not accept connection  : org.apache.activemq.transport.tcp.ExceededMaximumConnectionsException: Exceeded the maximum number of allowed
client connections. See the 'maximumConnections' property on the TCP transport configuration URI in the ActiveMQ configuration file (e.g., activemq.xml)

二、问题排查

消息队列堆积太多，导致jvm内存不足，浏览器访问mq后台管理页面发现有很多无用的消息队列

三、解决方式

配置自动清除无用的消息队列，打开activemq.xml文件（\apache-activemq-5.14.3\conf\activemq.xml），broker节点添加schedulePeriodForDestinationPurge="10000"
broker节点下的destinationPolicy添加以下红色参数：

<destinationPolicy>
            <policyMap>
              <policyEntries>
                <policyEntry topic=">" gcInactiveDestinations="true" inactiveTimoutBeforeGC="30000">
                  <pendingMessageLimitStrategy>
                    <constantPendingMessageLimitStrategy limit="1000"/>
                  </pendingMessageLimitStrategy>
                </policyEntry>
              </policyEntries>
            </policyMap>
</destinationPolicy>

参数含义：
schedulePeriodForDestinationPurge：10000 每十秒检查一次，默认为0，此功能关闭
gcInactiveDestinations： true 删除掉不活动队列，默认为false
inactiveTimoutBeforeGC：30000 不活动30秒后删除，默认为60秒

配置后，重启mq服务器即可