Tomcat OutOfMemoryError Java heap space Arrays.copyOf

Question

We have an servlet that uploads files from customers and stores them on our server. Every few weeks the servlet fails with the following error:

java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOf(Arrays.java:2882)
    at java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.java:100)
    at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:390)
    at java.lang.StringBuffer.append(StringBuffer.java:224)
    at java.util.logging.SimpleFormatter.format(SimpleFormatter.java:74)
    at org.apache.juli.FileHandler.publish(FileHandler.java:129)
    at java.util.logging.Logger.log(Logger.java:458)
    at java.util.logging.Logger.doLog(Logger.java:480)
    at java.util.logging.Logger.logp(Logger.java:680)
    at org.apache.juli.logging.DirectJDKLog.log(DirectJDKLog.java:167)
    at org.apache.juli.logging.DirectJDKLog.error(DirectJDKLog.java:135)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:274)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:525)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
    at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
    at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
    at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:769)
    at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:698)
    at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:891)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
    at java.lang.Thread.run(Thread.java:619)

Tomcat is running with -Xmx256M. I'm not sure how to debug this memory leak - could it be something to do with the java.util.logger filling up?

Answer 1

You've probably got something that holds on to some object references and never lets go. It's not that the logger is filling up memory, but the logger probably runs most frequently and is therefore the first thing to notice if you do fill up your heap.

Answer 2

There probably isn't a memory leak; my guess is that someone tries to write a huge log message. Check the log settings.

Also check how much memory Tomcat uses on the manager page and how much is free. Depending on your web app, 256MB might not be enough.

One last explanation could be a denial of service attack or an attempt to trigger a Java bug to hack your server.