Troubleshooting Tomcat using Catalina log

We can get the catalina logs in $CATALINA_HOME/logs
Here we'll have a catalina.out
We can see some huge info in that log file. If we want to what exactly happens since the start of tomcat then we need to log that into a new file.
By default we have log rotation enabled on this logs.
For now let us stop tomcat and nullify the catalina.out file and then start tomcat to have some new info in the catalina.out

# service tomcat stop
# cd $CATALINA_HOME/logs
# :> catalina.out (or) cat /dev/null > catalina.out
# ll catalina.out
-rw-r----- 1 root root 0 Feb 18 16:19 catalina.out

# service tomcat start
# ll catalina.out
-rw-r----- 1 root root 17341 Feb 18 16:21 catalina.out

We can see the log being written after the start of tomcat.
Now we can notice the instance giving some information about the starting of tomcat, about the configuration for the startup, path of the servlet instance for which the log is responsible for, when the instance and the webapplications have started.
Also as we are not hosting any production applications on it we don't have any other information logged continuously to it as there is no running transaction on it.
And the last line in this log at this moment tells us how much time the tomcat instance has took to startup.
We can see how the issues can be logged in this log file.
As we previously configured another tomcat instance with some different port numbers let us change the config file of the first instance to use the connector port as 8010

Let us stop the tomcat instance, do the above change, start the second instance and then start the first instance.

 # cd $CATALINA_HOME
 # ./bin/catalina.sh stop
 # :> logs/catalina.out
 # vi conf/server.xml

Change port 8009 with 8010 and save the config file

 # cd $CATALINA_HOME2
 # ./bin/catalina.sh start
 # ps -ef | grep catalina | grep -v grep
 # cd $CATALINA_HOME
 # ./bin/catalina.sh start
 # ps -ef | grep catalina | grep -v grep

We can see 2 tomcat instances running, let us check the catalina.out log for the errors. We will see the following error in the log.

 18-Feb-2017 16:39:33.802 SEVERE [main] org.apache.catalina.core.StandardService.initInternal Failed to initialize connector [Connector
 [AJP/1.3-8010]]
 org.apache.catalina.LifecycleException: Failed to initialize component [Connector[AJP/1.3-8010]]
   at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:112)
   at org.apache.catalina.core.StandardService.initInternal(StandardService.java:549)
   at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:107)
   at org.apache.catalina.core.StandardServer.initInternal(StandardServer.java:875)
   at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:107)
   at org.apache.catalina.startup.Catalina.load(Catalina.java:606)
   at org.apache.catalina.startup.Catalina.load(Catalina.java:629)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:498)
   at org.apache.catalina.startup.Bootstrap.load(Bootstrap.java:311)
   at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:494)
 Caused by: org.apache.catalina.LifecycleException: Protocol handler initialization failed
   at org.apache.catalina.connector.Connector.initInternal(Connector.java:970)
   at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:107)
   ... 12 more
 Caused by: java.net.BindException: Address already in use
   at sun.nio.ch.Net.bind0(Native Method)
   at sun.nio.ch.Net.bind(Net.java:433)
   at sun.nio.ch.Net.bind(Net.java:425)
   at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
   at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
   at org.apache.tomcat.util.net.NioEndpoint.bind(NioEndpoint.java:210)
   at org.apache.tomcat.util.net.AbstractEndpoint.init(AbstractEndpoint.java:972)
   at org.apache.tomcat.util.net.AbstractJsseEndpoint.init(AbstractJsseEndpoint.java:237)
   at org.apache.coyote.AbstractProtocol.init(AbstractProtocol.java:558)
   at org.apache.catalina.connector.Connector.initInternal(Connector.java:968)
   ... 13 more

Here we need to see the below lines

 org.apache.catalina.core.StandardService.initInternal Failed to initialize connector [Connector
     [AJP/1.3-8010]]
 Caused by: java.net.BindException: Address already in use

This tells us that the application is failed to initialize the AJP Connector Port on 8010 as it is addressed already in use
Now to fix this let us stop tomcat and change the port back to 8009 in the $CATALINA_HOME/conf/server.xml
After this start both the instances and can notice that we don't have any issues in either of the instance

Managing tomcat application

Tomcat is a servlet application which is ready to use after download. There is no need of installing this application. We can directly start or stop it from the bin directory. So in such case we should go to the bin directory in the CATALINA_HOME or else we need to use the startup script along with its absolute path. And the same is needed to shut it down. We can use the below script to manage the tomcat application and we neither need to go to the CATALINA_HOME nor to use the absolute path. All we need to do is to change the permissions to make it executable and copy that to /sbin and /etc/init.d/ directories. If we copy this into /etc/init.d/ then also we need to mention the absolute path but we can easily memorize it as we know all the startup scripts exists there. But if we copy that into /sbin then there is absolutely no need of mentioning the path of the file. We can use this like below: # tomcat start|stop|restart|status #!/bin/bash # Author : Arjun S...

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