topic Re: Transaction Deadlock in Alfresco Archive

Transaction Deadlock

flavio_donze — Tue, 09 Apr 2013 14:56:50 GMT

I get the following exception wenn I run two workflows at the same time.com.microsoft.sqlserver.jdbc.SQLServerException: Transaction (Process ID 55) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction. at com.microsoft.sqlserver.j

Re: Transaction Deadlock

trademak — Tue, 09 Apr 2013 15:10:03 GMT

Hi Flavio,

For your use case, using the async attribute would make much more sense then introducing this receive task.
Could you try and test it with the async="true" attribute?

Best regards,

Re: Transaction Deadlock

flavio_donze — Wed, 10 Apr 2013 08:46:53 GMT

Hi trademak

Thanks for your quick reply!

The async="true" does solve the transaction problem and I can remove the hack!

The problem that I got now is the exception handling.
The workflow that causes the deadlocks does not have any user interaction, it consists of a bunch of serviceTasks.
Before adding the async="true", in case one of the serviceTasks threw an exception it was caught by the client and displayed in a message box.
Using the async="true", the client does not get notified if something went wrong, since the workflow is running asynchronous on the server.
I would like to catch the exception in the workflow and maybe create a user task or send a mail.

I studied the Activiti User Guide, but I can't find anything that fits, e.g. a listener or "catch" task.

Any idea how I can accomplish this?

greets and thanks
Flavio

Re: Transaction Deadlock

ronald_van_kuij — Wed, 10 Apr 2013 09:42:33 GMT

It is better to post new questions in new topics with a specific subject. That way they are easier to find for others with a similar issue.

Re: Transaction Deadlock

flavio_donze — Fri, 12 Apr 2013 11:52:55 GMT

Done that: http://forums.activiti.org/en/viewtopic.php?f=6&t=6349

Re: Transaction Deadlock

flavio_donze — Tue, 16 Apr 2013 08:43:48 GMT

I created a little test to reproduce this deadlock issue.

I tried to upload an attachment, but it does not seem to work "Could not upload attachment to ./files/387_8192b0846287b030284985893c1b7563.".

So here the code:

SimpleCommit.bpmn20.xml


<?xml version="1.0" encoding="UTF-8"?>

<definitions id="definitions"
             xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL"
             xmlns:activiti="http://activiti.org/bpmn"
             targetNamespace="http://www.activiti.org/bpmn2.0">

 <process id="SimpleCommit" isExecutable="true">
  <startEvent id="start"/>

  <sequenceFlow id="startToWait" sourceRef="start" targetRef="wait"/>
  <receiveTask id="wait" name="wait"/>
  <sequenceFlow id="waitToSleepTask" sourceRef="wait" targetRef="sleepTask"/>

  <serviceTask id="sleepTask" activiti:class="com.softmodeler.workflow.SleepTask">
  </serviceTask>

  <sequenceFlow id="sleepTaskToEnd" sourceRef="sleepTask" targetRef="end"/>

  <endEvent id="end"/>
 </process>

</definitions>

SleepTask.java


package com.softmodeler.workflow;

import org.activiti.engine.delegate.DelegateExecution;
import org.activiti.engine.delegate.JavaDelegate;

/**
 * @author created by Author: fdo, last update by $Author: $
 * @version $Revision: $, $Date: $
 */
public class SleepTask implements JavaDelegate {

 @Override
 public void execute(DelegateExecution execution) throws Exception {
  Thread.sleep(5000);
 }

}

Excecution Code


 public void startTest() {
  try {
   Thread thread1 = new Thread(new Runnable() {
    @Override
    public void run() {
     try {
      System.out.println("start 1");
      start("testuser1", "SimpleCommit");
      System.out.println("end 1");
     } catch (ServerException e) {
      e.printStackTrace();
     }
    }
   });
   thread1.start();
   Thread thread2 = new Thread(new Runnable() {
    @Override
    public void run() {
     try {
      System.out.println("start 2");
      start("testuser2", "SimpleCommit");
      System.out.println("end 2");
     } catch (ServerException e) {
      e.printStackTrace();
     }
    }
   });
   thread2.start();
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 @Transactional(propagation = Propagation.REQUIRED, rollbackFor = Exception.class)
 protected String start(String initiator, String processKey) throws ServerException {
  String processInstanceId = null;
  try {
   identiyService.setAuthenticatedUserId(initiator);
   ProcessInstance instance = runtimeService.startProcessInstanceByKey(processKey);
   processInstanceId = instance.getId();
  } catch (Throwable e) {
   throw ServerUtil.createServerException(e);
  } finally {
   identiyService.setAuthenticatedUserId(null);
  }

  Execution execution = runtimeService.createExecutionQuery().processInstanceId(processInstanceId).activityId("wait") //$NON-NLS-1$
    .singleResult();
  if (execution != null) {
   // remove current user otherwise subprocesses are also listed (remove as well)
   identiyService.setAuthenticatedUserId(null);
   runtimeService.signal(execution.getId());
  }

  return processInstanceId;
 }

Maybe this can be added as a test?
greets
Flavio

Re: Transaction Deadlock

jbarrez — Tue, 16 Apr 2013 11:25:16 GMT

Does this happen on every database or only on sql server?

Re: Transaction Deadlock

flavio_donze — Wed, 17 Apr 2013 07:17:45 GMT

Right now I'm using MSSQL 2008 R2.

I will try to setup a postgresql environment.

Re: Transaction Deadlock

ronald_van_kuij — Wed, 17 Apr 2013 09:03:49 GMT

Might be related to an interesting mssql 'feature', lock escalation

http://www.sqlhacks.com/FAQs/Lock-Escalation

Re: Transaction Deadlock

flavio_donze — Fri, 19 Apr 2013 12:39:43 GMT

I tested it with postgresql and there was no deadlock.

I will have a lock at the lock-escalation, thanks for the hint Ronald.