topic Re: conflicts in database connections in JTA in Alfresco Archive

conflicts in database connections in JTA

tbee — Thu, 20 Sep 2012 12:43:48 GMT

I've got a setup where business model and Activiti are mixed into one engine. In order to facilitate transactional consistency, Bitronix JTA-XA is used to enabled distributed transactions. Configuration wise this works, however during the execution of a Activiti listener the connections have a confl

Re: conflicts in database connections in JTA

tbee — Thu, 20 Sep 2012 14:10:29 GMT

One more example, this is done within one JTA transaction:


2012-09-20 16:04:13,047 DEBUG #22433263[C18131420] activiti: [1] setString=27101 / java.lang.String / insert into ACT_RU_EXECUTION (ID_, …
…
2012-09-20 16:04:13,329 DEBUG #925089[C16330489] activiti: [1] setString=27101 / java.lang.String / select E.*         from ACT_RU_EXECUTION …

That last line returns null since it uses a different connection than the insert. The last line is the result of:


  List<ProcessInstance> lProcessInstances = lProcessEngine.getRuntimeService().createProcessInstanceQuery().processInstanceId(processInstanceId).list();

Can I configure Activiti (Hibernate) to use the same connection for read and write?

Re: conflicts in database connections in JTA

tbee — Thu, 20 Sep 2012 14:29:51 GMT

Confirmed! In non JTA mode Activiti uses one JDBC connection for all three statements (408, 432, 877). I'm filing a bug.

Re: conflicts in database connections in JTA

meyerd — Sun, 23 Sep 2012 05:59:34 GMT

Hi tbee,

when you do


ProcessEngines.getDefaultProcessEngine().getRuntimeService().setVariable( getWorkflowProcessInstance().getProcessInstanceId(), "validateOfferStage", Long.valueOf(System.currentTimeMillis()));

a new command is executed which opens a new mybatis session. In this session, a connection to the database is obtained. You write that you setup the environment with Bitronix yourself. Are you using a JTA aware datasource? When you are using an Java EE application server, the JCA database connector make sure that whenever you obtain a JDBC connection and already obtained one in the same JTA transaction, you get the same connection.

I would invite you to run you test in a Java EE application server like Jboss 7 or Glassfish 3 since there all of this is already setup correctly.

Read: http://jbossts.blogspot.de/2012/01/connecting-dots.html

Re: conflicts in database connections in JTA

tbee — Sun, 23 Sep 2012 06:14:53 GMT

In the Jira issue

https://jira.codehaus.org/browse/ACT-1385

Frederick Heremans says The default activiti behavior uses thread-local/datasource transaction management or a similar mechanism, which results in reusing the open connection from the 1st context. When using JTA for handling transactions however, a new transaction is created with a new connection.

So he confirms that there is a different connection management in normal vs JTA mode. Naturally my opinion is that there should not be; if code runs in normal mode, it should also in JTA. So the question is: why is there a different handling? Is there a good reason to do so? Why can't the connection in JTA mode be reused as well?

I'm using Postgres 9.1, the driver is JTA-XA compatible. I've made a work around for my current code (no idea what I will run into in the future) by attaching the ExeuctionDelegate and TaskDelegate to the current thread in the listeners, and use that further down in a custom setVariable.

Re: conflicts in database connections in JTA

meyerd — Sun, 23 Sep 2012 07:53:39 GMT

Hi tbee,

You need a JTA-transaction-aware datasource proxy. This has nothing to do with the database driver. You need a datasource that integrates with your transaction manager, such that you always use the same connection in the same transaciton.

Have you used this:
http://docs.codehaus.org/display/BTM/JdbcConfiguration2x
?

Make sure to set
shareTransactionConnections=true

Re: conflicts in database connections in JTA

meyerd — Sun, 23 Sep 2012 07:58:21 GMT

Frederick Heremans says The default activiti behavior uses thread-local/datasource transaction management or a similar mechanism, which results in reusing the open connection from the 1st context. When using JTA for handling transactions however, a new transaction is created with a new connection.

This is wrong BTW. You only get a new connection, if you open a new JTA transaction. the default behavior is that the 2nd context participates in the transaction opened by the first context. If you would open a new transaction for the second command, you would get a new connection.

Compare this to REQUIRED vs. REQUIRES_NEW in EJB.

Re: conflicts in database connections in JTA

tbee — Sun, 23 Sep 2012 08:09:01 GMT

That could very well be wrong, I do not know. The only point I think is relevant is that IMHO Activiti should behave identically in normal and JTA mode.

Re: conflicts in database connections in JTA

meyerd — Sun, 23 Sep 2012 08:14:43 GMT

The only point I think is relevant is that IMHO Activiti should behave identically in normal and JTA mode.

It does, if you setup JTA correctly! Just try it in Jboss or Glassfish.

Re: conflicts in database connections in JTA

tbee — Sun, 23 Sep 2012 08:43:49 GMT

I do not see how I could have made an error in setting my unit test environment up.
- I create a single DataSource in Bitronix
- I assign this DataSource to a JNDI name (using Glassfishes JNDI implementation)
- I tell Activiti to use JTA and specify the JNDI name

Where could I have made a mistake?

Tom

Re: conflicts in database connections in JTA

meyerd — Sun, 23 Sep 2012 08:59:05 GMT

I wrote earlier:

Make sure to set
shareTransactionConnections=true

In https://jira.codehaus.org/secure/attachment/61422/BitronixTrial.java
you are missing the shareTransactionConnections=true have you added this in the meantime?

Re: conflicts in database connections in JTA

tbee — Mon, 24 Sep 2012 08:11:12 GMT

BTW, the essence of this code is attached to the Jira issue, so it should be fairly easy to reproduce.

@meyerd: sorry, I had not seen your reply yet. I will test that tomorrow!

Re: conflicts in database connections in JTA

tbee — Tue, 25 Sep 2012 07:12:13 GMT

That option does not exist.

Invalid property 'shareTransactionConnections' of bean class [org.activiti.engine.impl.cfg.StandaloneProcessEngineConfiguration]: Bean property 'shareTransactionConnections' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?

Re: conflicts in database connections in JTA

meyerd — Tue, 25 Sep 2012 09:17:34 GMT

Hi tbee,

it is not a property in activiti but a property on the Bitronix PoolingDataSource

Re: conflicts in database connections in JTA

tbee — Tue, 25 Sep 2012 09:25:30 GMT

Sorry. No difference. It's still using a different connection.

Re: conflicts in database connections in JTA

tbee — Tue, 25 Sep 2012 09:29:57 GMT

Let me take that back. Too many file and configurations running around. It seems to work. More testing…

Re: conflicts in database connections in JTA

jbarrez — Wed, 26 Sep 2012 07:53:28 GMT

That's great news. Please report back if it works, so future generations can learn from it.

@Daniel: thanks, didn't knew about that property!

Re: conflicts in database connections in JTA

tbee — Wed, 26 Sep 2012 08:55:15 GMT

I didn't either 🙂

But so far so good. I'm planning a blog post about this next week.

Re: conflicts in database connections in JTA

jbarrez — Mon, 01 Oct 2012 11:30:57 GMT

Awesome. Keep us posted!

Re: conflicts in database connections in JTA

tbee — Tue, 02 Oct 2012 17:29:21 GMT

Here is the blog:
http://tbeernot.wordpress.com/2012/10/02/stand-alone-business-model-with-activiti-eclipselink-and-unit-tests-on-postgresql/