Getting java heap space issues in Tomcat 7

Question

I am working on a Java EE web application, which consists of Struts, Spring and Hibernate. In that, I get the following exceptions repeatedly (at least once a day).

Exception 1 :

Exception in thread "Timer-0" java.lang.OutOfMemoryError: Java heap space
    at java.util.LinkedHashMap.createEntry(LinkedHashMap.java:424)
    at java.util.LinkedHashMap.addEntry(LinkedHashMap.java:406)
    at java.util.HashMap.put(HashMap.java:385)
    at sun.util.resources.OpenListResourceBundle.loadLookup(OpenListResourceBundle.java:118)
    at sun.util.resources.OpenListResourceBundle.loadLookupTablesIfNecessary(OpenListResourceBundle.java:97)
    at sun.util.resources.OpenListResourceBundle.handleGetObject(OpenListResourceBundle.java:58)
    at sun.util.resources.TimeZoneNamesBundle.handleGetObject(TimeZoneNamesBundle.java:59)
    at java.util.ResourceBundle.getObject(ResourceBundle.java:368)
    at java.util.ResourceBundle.getObject(ResourceBundle.java:371)
    at java.util.ResourceBundle.getStringArray(ResourceBundle.java:351)
    at sun.util.TimeZoneNameUtility.retrieveDisplayNames(TimeZoneNameUtility.java:100)
    at sun.util.TimeZoneNameUtility.retrieveDisplayNames(TimeZoneNameUtility.java:81)
    at java.util.TimeZone.getDisplayNames(TimeZone.java:399)
    at java.util.TimeZone.getDisplayName(TimeZone.java:350)
    at java.text.SimpleDateFormat.subFormat(SimpleDateFormat.java:1110)
    at java.text.SimpleDateFormat.format(SimpleDateFormat.java:899)
    at java.text.SimpleDateFormat.format(SimpleDateFormat.java:869)
    at java.text.DateFormat.format(DateFormat.java:316)
    at org.apache.log4j.helpers.PatternParser$DatePatternConverter.convert(PatternParser.java:443)
    at org.apache.log4j.helpers.PatternConverter.format(PatternConverter.java:65)
    at org.apache.log4j.PatternLayout.format(PatternLayout.java:506)
    at org.apache.log4j.WriterAppender.subAppend(WriterAppender.java:310)
    at org.apache.log4j.DailyRollingFileAppender.subAppend(DailyRollingFileAppender.java:369)
    at org.apache.log4j.WriterAppender.append(WriterAppender.java:162)
    at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
    at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:66)
    at org.apache.log4j.Category.callAppenders(Category.java:206)
    at org.apache.log4j.Category.forcedLog(Category.java:391)
    at org.apache.log4j.Category.log(Category.java:856)
    at com.mchange.v2.log.log4j.Log4jMLog$Log4jMLogger.log(Log4jMLog.java:161)
    at com.mchange.v2.log.log4j.Log4jMLog$Log4jMLogger.warning(Log4jMLog.java:221)
    at com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector.run(ThreadPoolAsynchronousRunner.java:624)

Exception 2 :

Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1" java.lang.OutOfMemoryError: GC overhead limit exceeded
    at java.util.HashMap.addEntry(HashMap.java:753)
    at java.util.HashMap.put(HashMap.java:385)
    at java.util.HashSet.add(HashSet.java:200)
    at com.mchange.v2.c3p0.util.ConnectionEventSupport.addConnectionEventListener(ConnectionEventSupport.java:39)
    at com.mchange.v2.c3p0.impl.NewPooledConnection.addConnectionEventListener(NewPooledConnection.java:237)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishResourceOnCheckin(C3P0PooledConnectionPool.java:292)
    at com.mchange.v2.resourcepool.BasicResourcePool.attemptRefurbishResourceOnCheckin(BasicResourcePool.java:1606)
    at com.mchange.v2.resourcepool.BasicResourcePool.access$200(BasicResourcePool.java:32)
    at com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask.run(BasicResourcePool.java:1228)
    at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#4" java.lang.OutOfMemoryError: GC overhead limit exceeded
Exception in thread "Task-Thread-for-com.mchange.v2.async.ThreadPerTaskAsynchronousRunner@6c8bb765" java.lang.OutOfMemoryError: GC overhead limit exceeded
Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#3" java.lang.OutOfMemoryError: GC overhead limit exceeded
Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2" java.lang.OutOfMemoryError: GC overhead limit exceeded
Exception in thread "Task-Thread-for-com.mchange.v2.async.ThreadPerTaskAsynchronousRunner@6c8bb765" java.lang.OutOfMemoryError: GC overhead limit exceeded
Exception in thread "Task-Thread-for-com.mchange.v2.async.ThreadPerTaskAsynchronousRunner@6c8bb765" java.lang.OutOfMemoryError: GC overhead limit exceeded
Exception in thread "Timer-0" java.lang.OutOfMemoryError: Java heap space
Exception in thread ""http-bio-8080"-exec-2" java.lang.OutOfMemoryError: Java heap space
Exception in thread ""http-bio-8443"-Acceptor-0" java.lang.OutOfMemoryError: Java heap space
Exception in thread ""http-bio-8080"-exec-3" java.lang.OutOfMemoryError: Java heap space
Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#4" java.lang.OutOfMemoryError: GC overhead limit exceeded

And this is my configuration :

-server -Xms2048m -Xmx2048m
-XX:NewSize=1024m -XX:MaxNewSize=1024m -XX:PermSize=512m
-XX:MaxPermSize=1024m -XX:+DisableExplicitGC"

Can anyone please point out that am I getting this exceptions because of this configurations or anything else ?

I know that there is some issue in my code but how can I predict out to find those issues ? I have tried Eclipse MAT to analyse memory dumps but didn't get any idea though.

I have already tried to increase memory for this but it didn't help much except just reducing the frequency of this exceptions.

Please help. Thanks in advance.

Answer 1

There are two options on why you're getting these exceptions. First your application may simply need this much memory. Second your application leaks memory. In either case MAT is a good tool to diagnose the issue. A good starting point are the dominator tree and the leak suspect report.