重复启动Tomcat时，大概率出现Deploying web application direct

Posted 2020-11-17

由前一篇文章开始折腾supervisor，想玩玩tomcat异常退出后使用supervisor自动让tomcat重新启动，
随即丢了一个tomcat在服务器里面，本来就没有放任何项目，空跑在那边，只是tomcat有个界面就看看起没起来。
 
于是手动停止tomcat的进程触发supervisor自动拉起服务，应该是没有问题的，但是，来来回回启动了个两三次，突然发现，tomcat竟然起不来了！

随即查阅下日志：
 

[email protected] bin]# tail -f ../logs/catalina.out
19-Jun-2018 15:57:06.666 INFO [main] org.apache.coyote.AbstractProtocol.init Initializing ProtocolHandler ["ajp-nio-8009"]
19-Jun-2018 15:57:06.667 INFO [main] org.apache.tomcat.util.net.NioselectorPool.getSharedSelector Using a shared selector for servlet write/read
19-Jun-2018 15:57:06.667 INFO [main] org.apache.catalina.startup.Catalina.load Initialization processed in 535 ms
19-Jun-2018 15:57:06.684 INFO [main] org.apache.catalina.core.StandardService.startInternal Starting service Catalina
19-Jun-2018 15:57:06.684 INFO [main] org.apache.catalina.core.StandardEngine.startInternal Starting Servlet Engine: Apache Tomcat/8.1.15
19-Jun-2018 15:57:06.690 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory /opt/apache-tomcat-8.1.15-server/webapps/ROOT

 
卡在这个启动状态至少由10分钟才能完全启动起来，而且每次都这样。。。空跑都能这么操蛋？部署个项目还得了？难道要半小时？

网上查阅到有个大神写的文章，大意就是下面这句话：
 

The library used for random number generation in Sun‘s JVM relies on /dev/random by default for UNIX platforms. This can potentially block the Oracle WebLogic Communication Services process because on some operating systems /dev/random waits for a certain amount of "noise" to be generated on the host machine before returning a result. Although /dev/random is more secure, Oracle recommends using /dev/urandom if the default JVM configuration delays Oracle WebLogic Communication Services startup.

To determine if your operating system exhibits this behavior, try displaying a portion of the file from a shell prompt:

head -n 1 /dev/random
Open the $JAVA_HOME/jre/lib/security/java.security file in a text editor.

Change the line:

securerandom.source=file:/dev/random
to read:

securerandom.source=file:/dev/urandom
Save your change and exit the text editor.

 
就是linux提供随机数设备是/dev/random 和/dev/urandom，一般我们都只是都使用"/dev/random"，这个参数做随机数（因为每本操蛋的书都是这么写的！也没人说过为啥。）
 
两个有区别，urandom安全性没有random高，但random需要时间间隔生成随机数。jdk默认调用random。
 
所以根据上面的说法，修改配置文件：
 

find / -name securerandom.source

 
找到Java.security文件，在文件中找到securerandom.source这个设置项，将其改为：
 

securerandom.source=file:/dev/urandom

 
修改完毕后，重启tomcat，瞬间启动完毕。