Greeting,

We are running our web application on tomcat6 in cloud server. Filesystem is ext3, disk total is 160Gb, 4 x CPU@2200Mhz. Memory is 4Gb.

Recently, the site hanging happened many times. The site is totally unresponsive in the hung state. I can only see a loading status in browser. As a result, we have to restart tomcat. Online users seemed not too high at hunging time. No special clues can be found in log file. We can still use command to communicate with mysql server. Can anyone provide me some clues to investigate?

I think there is something wrong with database connection or pool. If so, I also hope someone can provide me some suggestion on parameters of database pool configuration (c3p0).

Tools we are using: Lucene2.1.0, hibernate search3.2.0 , hibernate 3.5.0 and spring2.5 Database: mysql

I set max_connections in mysql to 300.

Datasource is configured as follows:

<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="driverClass" value="com.mysql.jdbc.Driver"/>
<property name="jdbcUrl" value="jdbc:mysql://localhost:3306/database_v3"/>
<property name="maxPoolSize" value="200"/>
<property name="minPoolSize" value="5"/>
<property name="acquireIncrement" value="5"/>
<property name="maxIdleTime" value="300"/>
<property name="maxStatements" value="100"/>
<property name="numHelperThreads" value="3"/>
<property name="breakAfterAcquireFailure" value="false"/>
<property name="testConnectionOnCheckout" value="false"/>
<property name="checkoutTimeout" value="2000"/>
<property name="acquireRetryDelay" value="1000"/>
<property name="acquireRetryAttempts" value="60"/>
<property name="idleConnectionTestPeriod" value="60"/>
<property name="properties">
<props>
<prop key="user">root</prop>
<prop key="password">password</prop>
</props>
</property>
</bean>

300 connections is a huge number (use something like 20). Nevertheless I doubt it is a hanging cause. Use remote debugger or profiler to check where the site hangs.

r,

The default of "max connection" in mysql is 100. I set maxPoolSize to 200 in c3p0 configuration. Considering a different service uses same mysql server, I increased "max connection" in mysql to 300.

Ian

r,

can you recommend a profiler tools for me?

thanks

I would first try to use built-in debugger. Just run tomcat in debug mode. Then connect to it and list all the threads. You should see where the main thread hanged-up. If this is really connection or pool related you will see that the thread hanged on connection opening.

This could, for example, happen if your application is not releasing connections after usage. You could also try to check MySQL monitoring tools to check if all possible pool connections are indeed busy when server hangs.