I have seen instances of a HashMap whose entries got circularly linked, I assume, due to updates which where not thread safe. Any thread using a get() on such a HashMap will spin forever chasing its tail.
Cheers, Larry > -----Original Message----- > From: Leon Rosenberg [mailto:[EMAIL PROTECTED] > Sent: Tuesday, September 06, 2005 8:31 AM > To: tomcat-user@jakarta.apache.org > Subject: Tomcat/JVM hangs in session.getAttribute / HashMap.get() > > Hi, > > This is quite ugly but we are running out of ideas. > > We are currently experiencing stange behaviour of tomcat (or the VM). > > Our tomcat hangs (not reproduceable, but probably on parallel > requests to similar methods) in session.getAttibute(): > > We checked the source code of the HashMap, StandardSession > and StandardSessionFacade but couldn't find any synchronized methods. > The manager shows the 4 threads hanging since 4000000 millis > (more than an hour). > > we created a stacktrace with kill - QUIT, here the threads are: > > > "http-8580-Processor3" daemon prio=1 tid=0x7cdf11d0 > nid=0x3269 runnable [7d7fe000..7d7ff8bc] > at java.util.HashMap.get(HashMap.java:325) > at > org.apache.catalina.session.StandardSession.getAttribute(Stand > ardSession.java:975) > at > org.apache.catalina.session.StandardSessionFacade.getAttribute > (StandardSessionFacade.java:109) > at > de.friendscout.datingr4.shared.presentation.action.BaseAction. > getUserId(BaseAction.java:653) > at > de.friendscout.datingr4.onlinearea.presentation.action.BaseOnl > ineAreaAction.getSettings(BaseOnlineAreaAction.java:89) > at > de.friendscout.datingr4.onlinearea.presentation.action.GetOnli > neUsersAction.doExecute(GetOnlineUsersAction.java:49) > > > "http-8580-Processor1" daemon prio=1 tid=0x7d3fa078 > nid=0x3269 runnable [7ce7f000..7ce7f8bc] > at java.util.HashMap.get(HashMap.java:325) > at > org.apache.catalina.session.StandardSession.getAttribute(Stand > ardSession.java:975) > at > org.apache.catalina.session.StandardSessionFacade.getAttribute > (StandardSessionFacade.java:109) > at > de.friendscout.datingr4.shared.presentation.action.BaseAction. > getUserId(BaseAction.java:653) > at > de.friendscout.datingr4.onlinearea.presentation.action.ShowFil > tersAction.doExecute(ShowFiltersAction.java:42) > at > de.friendscout.datingr4.shared.presentation.action.BaseAction. > execute(BaseAction.java:316) > > > > "http-8580-Processor24" daemon prio=1 tid=0x7d430200 > nid=0x3269 runnable [7e77f000..7e77f8bc] > at java.util.HashMap.get(HashMap.java:325) > at > org.apache.catalina.session.StandardSession.getAttribute(Stand > ardSession.java:975) > at > org.apache.catalina.session.StandardSessionFacade.getAttribute > (StandardSessionFacade.java:109) > at > de.friendscout.datingr4.shared.presentation.util.RealmUtility. > initRealm(RealmUtility.java:66) > at > de.friendscout.datingr4.shared.presentation.util.RealmUtility. > initRealm(RealmUtility.java:61) > at > de.friendscout.datingr4.shared.presentation.controller.Control > lerServlet.doGet(ControllerServlet.java:139) > > > My Java knowledge isn't sufficent to explain how something can hang in > HashMap.get() since its not synchronized. Neither are the > .getAttribute() methods of the StandardSession or > StandardSessionFacade. > > We are using jdk 1.4.2_08-b03, tomcat 5.0.25, struts 1.1, > jacorb 2.2 (night build) on linux/debian/sarge - 3.1 stable. > > any ideas? anybody? > > regards > Leon > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
