我负责ActiveMQ服务，本周一队列消费者的系统反馈他们无法正常监听到消息了，从MQ Console上看到该队列A的消息确实堆积了，Number Of Pending Messages 不断增加，本地开启消费者以及他们系统本地开启消费者都能正常监听到消息，但是线上就是不行，他们服务重启后问题依然无法解决，找不到解决的办法，我就考虑升级下AMQ版本，原版本为5.8.0（可从MQ Console中看到）。
从网上下载到最新版本：5.15.9，上传到服务器上后，修改了conf目录下activemq.xml的TCP端口号（生产者推送和消费者监听的端口）以及jetty.xml中的控制台端口号后，重启服务，提示PID已创建，但是ps查看进程，却找不到该进程信息，并且telnet本TCP端口，也不通，查看data目录下的activemq.log，发现文件修改时间还是3月份。
找不到更多提示信息，只好硬下头皮（shell水平有待提高）去读下bin目录下的启动脚本：activemq，看到有Detect the location of the java binary，突然想起来MQ是依赖JDK的，而服务器还是JDK1.6，新版本MQ可能不兼容，搜索下发现确认5.15.9版本需要JDK1.8。网上查找AMQ指定JDK目录，在bin目录下env文件中最后一段信息中发现是使用：JAVACMD="auto"自动去服务器上查找，通过which java查看（/usr/bin/java）
The server is indeed JDK1.6. After installing JDK1.8, modify the JAVACMD in the env file and assign it to /aaa/jdk1.8.0_144/bin/java under the JDK. Restarting the service will still not work. . .
Did the configuration not take effect, increase the output in the startup script activemq in the bin directory: echo $ JAVACMD, and found that it is still / usr / bin / java, strangely, the JAVACMD configuration item does not take effect, is the specified JDK directory not correct, just change the directory /aaa/jdk1.8.0_144/bin, restarting the service will still not work, but. . . The JAVACMD directory echoed is /aaa/jdk1.8.0_144/bin. Go to the /aaa/jdk1.8.0_144 and /aaa/jdk1.8.0_144/bin directories to view. The user who logged in the java file does not have x executable permissions , Without considering why there is no permission, first increase the permissions by chmod, and then adjust JAVACMD to /aaa/jdk1.8.0_144/bin/java, start, the service finally starts normally, and the console can also be viewed normally.
