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How can i catch java.lang.OutOfMemoryError: Java heap space? I have server which the work some times and after that throw java.lang.OutOfMemoryError: Java heap space. But I can not faind place in code where it occurs. In logs not iformation where it occurs. We allocated 8 GB memory and error does not appear but server at some point in time it starts to occupy almost the entire memory. What tools will help me find the error?

I tried Visual JVM but it not helped. I can not faind code where memory leak

I can not emulate the situation when the server crashes

user5620472
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You can analyze the heap dump with some tool like JProfiler or VisualVM (there are many other tools and just mentioning two options here) to identify what kind of objects consume the most memory. This will give you an idea on the number of instances, memory consumption of different objects in you application. With that you will be able to figure out where the memory leak occurs.

Some tools like JProfiler lets you connect to a running JVM instance and track method call trees, locations of the code where a certain object is created etc, which will, combined with above details extracted from the heap dump, give you even more clues on where the memory leak occurs.

Rajeev Sampath
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java.lang.OutOfMemoryError: Java heap space

You must not catch it. The programmer is not required to do anything with these. In fact it is a bad idea to use a try-catch clause for Errors. Recovering from Error is not possible. The only solution to errors is to terminate the execution. Errors are related to environment in which application is running. Examples include OutOfMemoryError, StackOverflowError, etc.

Now if you are facing this error, It means its time to re-engineering your application.

  1. Check If you application closes all the resources gracefully, may in finally block or something like that.
  2. Check about the objects you are creating. Ask your self whether you really need any object to be created again and again, Can It be a singleton, What is the scope of that object- whether it is globally accesible, what is the life of that object.
  3. Try to minimize the scope of the object, I mean if its really important then make the object globally accessible.

To analyze the heap dump, you can excute the JVM with below parameters:

-XX:+HeapDumpOnOutOfMemoryError writes heap dump on OutOfMemoryError (recommended)

-XX:+HeapDumpOnCtrlBreak writes heap dump together with thread dump on CTRL+BREAK

There is a good article on it. You can see here. It may resolve your problem. You can also use jhat - Java Heap Analysis Tool, its comes in JDK bin directory.

pbajpai
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  • I have big server in production where some million users make some events and after 3-6 hours server crash. I can not emulate the situation when the server crashes. How can I check thousands of lines of code if I do not know where module is crash – user5620472 Jun 07 '16 at 04:56