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Blog 05/06/2012

Troubleshoot JVM crashes of WebLogic: CompilerThread problem

Tiny technicians fixing a small error

Somehow our WebLogic server running Enterprise Manager 11g sometimes dies and is restarted by NodeManager. The restart is of course very nice, but I’d rather see the WebLogic server keeps on running.

First thing to do is investigate the WebLogic server logfiles and the JVM logfiles

cd $ORACLE_HOME/../..//gc_inst/user_projects/domains/GCDomain/servers/EMGC_OMS1/logs/
 WLS logs: EMGC_OMS1.log*
 JVM logs: EMGC_OMS1.out*

The WLS serverlogs don’t show any clues to what has happened, but the JVM standard out (stdout) actually has logged a core dump.

# A fatal error has been detected by the Java Runtime Environment:
 #  SIGSEGV (0xb) at pc=0x00007fea60a26a8a, pid=6442, tid=1100994880
 # JRE version: 6.0_18-b07
 # Java VM: Java HotSpot(TM) 64-Bit Server VM (16.0-b13 mixed mode linux-amd64 )
 # Problematic frame:
 # V  [libjvm.so+0x248a8a]
 # An error report file with more information is saved as:
 # /u01/app/oracle/product/gc_inst/user_projects/domains/GCDomain/hs_err_pid6442.log
 # If you would like to submit a bug report, please visit:
 #   http://java.sun.com/webapps/bugreport/crash.jsp
 /u01/app/oracle/product/gc_inst/user_projects/domains/GCDomain/bin/startWebLogic.sh: line 193:  6442 Aborted                 (core dumped) ${JAVA_HOME}/bin/java ${JAVA_VM} ${MEM_ARGS} -Dweblogic.Name=${SERVER_NAME} -Djava.security.policy=${WL_HOME}/server/lib/weblogic.policy ${JAVA_OPTIONS} ${PROXY_SETTINGS} ${SERVER_CLASS}
 <Jun 5, 2012 10:33:53 AM> <FINEST> <NodeManager> <Waiting for the process to die: 6392>
 <Jun 5, 2012 10:33:53 AM> <INFO> <NodeManager> <Server failed so attempting to restart (restart count = 1)>

Let’s look into logfile: /u01/app/oracle/product/gc_inst/user_projects/domains/GCDomain/hs_err_pid6442.log.

There are actually three more of these hs_err logfiles and the same number of linux coredumps. Examining the hs_err logfile shows us some relevant information to pin-point the root cause. I’ve trimmed the output to make it more readable for this specific case.  The clues to follow:

  1. Thread section: SIGSEGV on CompilerThread. The compiler is giving us throubles.
  2. Compile task: oracle.sysman.emo.perf.metric.rt.DbAshRollupMetric._getData. This is the class being compiled when compiler choked.
  3. Process section: All threads in _thread_blocked state and Compiler Thread in _thread_in_native state.
---------------  T H R E A D  ---------------
Current thread (0x00007fea16e59800):  JavaThread "CompilerThread0" daemon [_thread_in_native, id=6468, stack(0x00000000418fd000,0x00000000419fe000)]

siginfo:si_signo=SIGSEGV: si_errno=0, si_code=1 (SEGV_MAPERR), si_addr=0x0000000000000000
Current CompileTask:
C2:188% !   oracle.sysman.emo.perf.metric.rt.DbAshRollupMetric._getData(ZLjava/util/Date;Ljava/lang/Object;J)Loracle/sysman/emSDK/emd/dtd/MetricResult; @ 165 (1478 bytes)
---------------  P R O C E S S  ---------------

Java Threads: ( => current thread )
  0x00007fea16e5b000 JavaThread "Low Memory Detector" daemon [_thread_blocked, id=6470, stack(0x00000000410d3000,0x00000000411d4000)]
  0x00007fea164ef800 JavaThread "CompilerThread1" daemon [_thread_blocked, id=6469, stack(0x00000000420d5000,0x00000000421d6000)]
=>0x00007fea16e59800 JavaThread "CompilerThread0" daemon [_thread_in_native, id=6468, stack(0x00000000418fd000,0x00000000419fe000)]
  0x00007fea16eb1800 JavaThread "MultiThreadedHttpConnectionManager cleanup" daemon [_thread_blocked, id=6467, stack(0x00000000417fc000,0x00000000418fd000)]
  0x00007fea16e51000 JavaThread "AD Thread Pool-Global1" daemon [_thread_blocked, id=6466, stack(0x0000000041ad6000,0x0000000041bd7000)]
  0x00007fea16e4f000 JavaThread "AD Thread Pool-Global0" daemon [_thread_blocked, id=6465, stack(0x0000000040616000,0x0000000040717000)]
  0x00007fea16df5000 JavaThread "AD Thread-Metric Reporter0" daemon [_thread_blocked, id=6464, stack(0x0000000040252000,0x0000000040353000)]
  0x00007fea16df4800 JavaThread "AD Thread-Config Poller" daemon [_thread_blocked, id=6463, stack(0x00000000416fb000,0x00000000417fc000)]
  0x00000000412a4000 JavaThread "Thread-0" daemon [_thread_blocked, id=6454, stack(0x000000004010a000,0x000000004020b000)]
  0x00000000412b6000 JavaThread "Signal Dispatcher" daemon [_thread_blocked, id=6451, stack(0x000000004050b000,0x000000004060c000)]
  0x0000000041297800 JavaThread "Finalizer" daemon [_thread_blocked, id=6450, stack(0x0000000040800000,0x0000000040901000)]
  0x0000000041290000 JavaThread "Reference Handler" daemon [_thread_blocked, id=6449, stack(0x0000000041ea9000,0x0000000041faa000)]
  0x0000000041208800 JavaThread "main" [_thread_blocked, id=6443, stack(0x0000000041c95000,0x0000000041d96000)]

Scanning through the other hs_err.log files I actually see that all crashes were caused when compiling the same class!

cd /u01/app/oracle/product/gc_inst/user_projects/domains/GCDomain
grep 'C2:' hc_err_*.log
hs_err_pid17546.log:C2:175% !   oracle.sysman.emo.perf.metric.rt.DbAshRollupMetric._getData(ZLjava/util/Date;Ljava/lang/Object;J)Loracle/sysman/emSDK/emd/dtd/MetricResult; @ 165 (1478 bytes)
hs_err_pid25557.log:C2:187% !   oracle.sysman.emo.perf.metric.rt.DbAshRollupMetric._getData(ZLjava/util/Date;Ljava/lang/Object;J)Loracle/sysman/emSDK/emd/dtd/MetricResult; @ 165 (1478 bytes)
hs_err_pid6013.log:C2:198% !   oracle.sysman.emo.perf.metric.rt.DbAshRollupMetric._getData(ZLjava/util/Date;Ljava/lang/Object;J)Loracle/sysman/emSDK/emd/dtd/MetricResult; @ 165 (1478 bytes)
hs_err_pid6442.log:C2:188% !   oracle.sysman.emo.perf.metric.rt.DbAshRollupMetric._getData(ZLjava/util/Date;Ljava/lang/Object;J)Loracle/sysman/emSDK/emd/dtd/MetricResult; @ 165 (1478 bytes)

MOS note 1009131.1 describes what is happening when a compiler crash occurs. The JVM is compiling classes into native code (instead of doing interpreted execution). We actually have three options to work around this problem.

  1. use -client instead of -server (which is default in jdk 1.6);
  2. use -Xint to disable native compilation completely (for the whole JVM);
  3. use .hotspot_compiler file to selectively prevent classes from being compiled to native code.

As we have determined which class is giving is problems, we can implement option 3. We have to place the .hotspot_compiler file in the working directory of the JVM. We can determine the working directory by executing the following java utility.

/u01/app/oracle/product/jdk/bin/jinfo <PID of JVM>|grep user.dir
Attaching to process ID 3069, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 16.0-b13
user.dir = /u01/app/oracle/product/gc_inst/user_projects/domains/GCDomain

Now we create the .hotspot_compiler file in the user.dir with the following contents:

exclude oracle/sysman/emo/perf/metric/rt/DbAshRollupMetric._getData

Now we can restart the JVM and check wether the configuration is succesful. The fastest way to restart the Weblogic JVM of Enterprise Manager is by issuing a SIGKILL. Nodemanager will kick in and restart the Weblogic server.
Checking standard out (EMGC_OMS1.out) of the Weblogic JVM will show that we succeeded.

starting weblogic with Java version:
CompilerOracle: exclude oracle/sysman/emo/perf/metric/rt/DbAshRollupMetric._getData
java version "1.6.0_18"
Java(TM) SE Runtime Environment (build 1.6.0_18-b07)
Java HotSpot(TM) 64-Bit Server VM (build 16.0-b13, mixed mode)
Starting WLS with line:

Hope this helps…


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