Hi App Engine Team,
I see 100% error rate for a servlet in my application.
The function had been working well for months.
The lines of code that generate errors are as following:
List<Key<User>> memKeys = userDao.getUserKeys();
Map<Key<User>, User> mem = userDao.get(memKeys);
List<User> memList = new ArrayList<User>(mem.values());
Collections.sort(memList, comp);
Comparator<User> comp = new Comparator<User>()
{
@Override
public int compare(User user1, User user2)
{
int ret = user2.getGroupRank() - user1.getGroupRank();
if (ret == 0)
{
ret = ((user2.getRep() - user1.getRep()) >= 0 ? 1 : -1);
}
return ret;
}
};
The error is:
[27/Mar/2011:00:45:28 -0700] "POST /GM HTTP/1.1" 500 0 - "a.
2.3.0,gzip(gfe)" "pe-server2.appspot.com" ms=76 cpu_ms=140
api_cpu_ms=0 cpm_usd=0.003913
W 2011-03-27 00:45:28.770
/GM
java.lang.IllegalArgumentException: Comparison method violates its
general contract!
at java.util.TimSort.mergeLo(TimSort.java:747)
at java.util.TimSort.mergeAt(TimSort.java:483)
at java.util.TimSort.mergeCollapse(TimSort.java:408)
at java.util.TimSort.sort(TimSort.java:214)
at java.util.TimSort.sort(TimSort.java:173)
at java.util.Arrays.sort(Arrays.java:1347)
at java.util.Collections.sort(Collections.java:217)
at com.miracle.server.pe.GroupMember.doPost(GroupMember.java:46)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:
511)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1166)
at
com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:
97)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1157)
at
com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:
35)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1157)
at
com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:
43)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1157)
at
org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:
388)
at
org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:
216)
at
org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:
182)
at
org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:
765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:
418)
at
com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:
238)
at
org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:
152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:
542)
at org.mortbay.jetty.HttpConnection
$RequestHandler.headerComplete(HttpConnection.java:923)
at
com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:
76)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at
com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:
135)
at
com.google.apphosting.runtime.JavaRuntime.handleRequest(JavaRuntime.java:
261)
at com.google.apphosting.base.RuntimePb$EvaluationRuntime
$2.handleRequest(RuntimePb.java:9285)
at com.google.net.rpc.impl.RpcUtil.runRpcInApplication(RpcUtil.java:
437)
at com.google.net.rpc.impl.Server$RpcTask.runInContext(Server.java:
573)
at com.google.tracing.TraceContext$TraceContextRunnable
$1.run(TraceContext.java:448)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:
688)
at com.google.tracing.TraceContext
$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:
326)
at com.google.tracing.TraceContext
$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:
318)
at com.google.tracing.TraceContext
$TraceContextRunnable.run(TraceContext.java:446)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:
1110)
at java.util.concurrent.ThreadPoolExecutor
$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:636)
With some googling, I found that the error was related to JDK bugs.
I'm not using a sorted map or set which will possibly impose such
error:
"In particular the sorted set (or sorted map) will violate the general
contract for set (or map), which is defined in terms of equals." as in
http://download.oracle.com/javase/1.4.2/docs/api/java/util/Comparator.html
Is there anything I can do to fix the problem?
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