How to locate memory leaks in Tomcat logs

This article introduces how to troubleshoot memory leaks through Tomcat logs and related tools.

1. Memory monitoring and heap dump

First, use tools such as JVisualVM or jstat to monitor Tomcat's memory usage in real time, observe changes in heap memory, and determine whether there is a memory leak. Once a leak is suspected, use the jmap command to generate a heap dump file (heap.bin):

 jmap -dump:format=b,file=heap.bin<pid></pid>

in<pid></pid> is the Tomcat process ID.

2. Heap dump file analysis

Use the Eclipse Memory Analyzer Tool (MAT) or other tools to open the heap.bin file and analyze the cause of the memory leak. MAT can effectively identify leak points and display object reference relationships.

3. Log analysis

Check the Tomcat log file for errors or warning messages related to memory leaks. For example, Tomcat logs ThreadLocal leak warnings, such as:

 <code>org.apache.catalina.loader.WebappClassLoaderBase.checkThreadLocalMapForLeaks: The web application [ttt] created a ThreadLocal ...</code>

4. GC log analysis

Enable GC logs to analyze abnormal memory growth or frequent GC behavior. Enable GC logs with the following JVM parameters:

 -XX: PrintGCDetails -XX: PrintGCDateStamps -Xloggc:gc.log

Then use tools such as GCViewer or GCEasy to parse the gc.log file.

5. Code optimization and JVM parameter adjustment

According to the analysis results, check the parts of the code that may cause memory leaks, such as resource not being closed correctly, holding large object references for a long time, etc. If necessary, adjust the JVM memory parameters (-Xms, -Xmx) to optimize performance.

Through the above steps, you can systematically troubleshoot and resolve memory leaks in Tomcat.

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