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

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.