6 Replies Latest reply on Sep 6, 2007 8:34 AM by vitamin c

    Write lock is not released

    St Ch Newbie

      Hi all,

      we have JBoss 4.0.2 , JBossCache 1.2.2 and Hibernate 3.1.
      Isolation level = repeatable read

      Ocasionay we observe a following in logs:
      1) thread x starts a transaction and obtains a write lock on resource A
      2) ~30 mins go by
      3) transaction in thread x fails to obtain a _read_ lock on resource A, since
      write lock is already held by thread x:


      [ReportDataTaskRunner-20521017-1] - Transaction failed due to exception
      org.hibernate.cache.CacheException: org.jboss.cache.lock.TimeoutException: read lock for Attribute#4558 could not be acquired by <zzz:4256>:162303 after 15000 ms. Locks: Read lock owners: []
      Write lock owner: Thread[ReportDataTaskRunner-20521017-1,5,jboss]
      , lock info: write owner=Thread[ReportDataTaskRunner-20521017-1,5,jboss] (activeReaders=0, activeWriter=Thread[ReportDataTaskRunner-20521017-1,5,jboss], waitingReaders=0, waitingWriters=0, waitingUpgrader=0)

      This lock stays forever.

      I'd appreciate any hints on this.

      Thanks in advance,
      Stas.

        • 1. Re: Write lock is not released
          Elias Ross Master

          What's the write thread doing? (Can you get a stack trace of your application at this time?)

          • 2. Re: Write lock is not released
            St Ch Newbie

             

            "genman" wrote:
            What's the write thread doing? (Can you get a stack trace of your application at this time?)


            Yep that's a good idea. However I do not have exact steps to reproduce this issue, and we observe it only ocassionaly in production. I'll try to reproduce it and get the stack trace.

            Thank you,
            Stas.

            • 3. Re: Write lock is not released
              St Ch Newbie

               

              "genman" wrote:
              What's the write thread doing? (Can you get a stack trace of your application at this time?)


              Meanwhile, any other ideas?

              • 4. Re: Write lock is not released
                Manik Surtani Master

                It looks like the current WL holder and the RL requestor are not the same:

                ... could not be acquired by <zzz:4256>:162303 ...
                


                and

                ... Write lock owner: Thread[ReportDataTaskRunner-20521017-1,5,jboss] ...
                


                A thread dump would be very helpful.

                In addition, what transaction manager (if any) have you configured for JBoss Cache (the TransactionManagerLookup attribute in your JBoss Cache cfg xml)?

                • 5. Re: Write lock is not released
                  St Ch Newbie

                   

                  "manik.surtani@jboss.com" wrote:
                  It looks like the current WL holder and the RL requestor are not the same:

                  ... could not be acquired by <zzz:4256>:162303 ...
                  


                  and

                  ... Write lock owner: Thread[ReportDataTaskRunner-20521017-1,5,jboss] ...
                  




                  A thread dump would be very helpful.

                  In addition, what transaction manager (if any) have you configured for JBoss Cache (the TransactionManagerLookup attribute in your JBoss Cache cfg xml)?


                  Oh, I see first time thread acquired WL without GlobalTransaction but then it tries to get a RL having one.

                  As for TransactionManagerLookup - we have TransactionManagerLookupClass attribute set to org.jboss.cache.JBossTransactionManagerLookup

                  Thank you,
                  Stas.

                  • 6. Re: Write lock is not released
                    vitamin c Newbie

                     

                    "manik.surtani@jboss.com" wrote:

                    It looks like the current WL holder and the RL requestor are not the same:
                    ... could not be acquired by <zzz:4256>:162303 ...
                    

                    and
                    ... Write lock owner: Thread[ReportDataTaskRunner-20521017-1,5,jboss] ...
                    


                    Is it OK that RL requestor thread uses a GlobalTransaction, whereas WL owner thread doesn't?

                    Here's the code, where a GlobalTransaction is assigned to a thread requesting a lock (either RL or WL):
                    package org.jboss.cache.interceptors;
                    ...
                    public class LockInterceptor extends Interceptor {
                    ...
                     public Object invoke(MethodCall m) throws Throwable {
                    ...
                     GlobalTransaction gtx=null;
                    ...
                     if(tx_mgr != null && (tx=tx_mgr.getTransaction()) != null && isValid(tx)) { // ACTIVE or PREPARING
                     if(!transactions.contains(tx)) {
                     gtx=cache.getCurrentTransaction(tx);
                     if(gtx == null)
                     throw new Exception("failed to get global transaction");
                    ...
                     else {
                     gtx=cache.getTransactionTable().get(tx);
                     }
                    ...
                    

                    Assuming that transaction manager presents, it is still unclear will a thread receive a non-null gtx, since cache.getTransactionTable().get(tx) doesn't check for null return value. According to metastaz's observations a thread may or may not receive a gtx, which looks like a bug, doesn't it?

                    Thanks,
                    Alexey