Java root cause java.lang.OutOfMemoryError error [duplicate]

This question already has answers here: Closed 12 years ago.

I am new to Java and given the task to fix a bug and the issue is as follows. It would be really great if you give suggestions/ideas what is this issue and how can I fix this.:

HTTP Status 500 - 

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type Exception report

message 

description The server encountered an internal error () that prevented it from fulfilling this request.

exception 

org.apache.jasper.JasperException
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:453)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:375)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspSe开发者_JS百科rvlet.java:314)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:368)


root cause 

javax.servlet.ServletException
    org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:858)
    org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:791)
    org.apache.jsp.CustMaint.Jsp.ProfProfileDetails_jsp._jspService(ProfProfileDetails_jsp.java:4016)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:368)


root cause 

java.lang.OutOfMemoryError


note The full stack trace of the root cause is available in the Apache Tomcat/5.5.17 logs.


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Apache Tomcat/5.5.17

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Here's what the Tomcat guys have to say:

An Out Of Memory can be thrown by several causes:

• A servlet trying to load a several GBytes file into memory will surely kill the server. These kind of errors must be considered a simple bug in our program.

• To compensate for the data your servlet tries to load, you increase the heap size so that there is no room to create the stack size for the threads that need to be created. The memory required by each thread will vary by OS but can be as high as 2M by default and in some OS's (like Debian Sarge) is not reducible with the -Xss parameter. 1 Rule of Thumb, use no more than 1G for heap space in a 32-bit web application.

• Deep recursive algorithms can also lead to Out Of Memory problems. In this case, the only fixes are increasing the thread stack size (-Xss), or refactoring the algorithms to reduce the depth, or the local data size per call.

• A webapp that uses lots of libraries with many dependencies, or a server maintaining lots of webapps could exhauste the JVM PermGen space. This space is where the VM stores the classes and methods data. In those cases, the fix is to increase this size. The Sun VM has the flag -XX:MaxPermSize that allows to set its size (the default value is 64M)

• Hard references to classes can prevent the garbage collector from reclaiming the memory allocated for them when a ClassLoader is discarded. This will occur on JSP recompilations, and webapps reloads. If these operations are common in a webapp having these kinds of problems, it will be a matter of time, until the PermGen space gets full and an Out Of Memory is thrown.

Source: Tomcat Wiki: OutOfMemory

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Well... who really caused the out of memory error?

If you ate 8 slices of pizza and you are full, is it the last slice that caused the out of stomach error?

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Use Java Heap Analysis Tool (JHAT) with Eclipse MAT http://www.eclipse.org/mat/ to analyse what's going on inside JVM. What is eating how much memory. See the profile and then see the code causing that.

You can also use JConsole, it's dead easy to set it up. And you can see stuffs 'live'. TPTP is also a good option, unfortunately, I find it hard to configure.

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This kind of problem is not easy to nail down based on just the stacktrace. It at least boils down to that you've either a memory leak in your application (the code is keeping (unnecessarily) too much objects for an (unnecessarily) long time in memory), or the server simply doesn't have enough memory in order to be able to run your webapp (simply because it is designed that way to require many memory).

To detect and fix memory leaks, use a Java profiler. If you don't have any memory leaks, i.e. the memory usage is stable but the code just really need that much memory, then simply give the server more memory to work with. The profiler is however still useful to spot memory holes in your webapp and optimize code accordingly.

If you're using Eclipse, use TPTP profiler or if you're using Netbeans, use builtin VisualVM profiler. Or when you're using standalone VisualVM, check this blog how to monitor Tomcat with it.