topic Re: Multi server environment in Alfresco Archive

Multi server environment

einszwo — Mon, 27 Apr 2015 08:28:59 GMT

Hi everyone,I have a question about using activiti in an environment where my application is deployed redundant on more than one server to ensure availability for the users. All applications pointing on the same database ( So only one db exists). My embedded process engine of course is part of the a

Re: Multi server environment

martin_grofcik — Mon, 27 Apr 2015 13:35:23 GMT

Hi Markus,

I want to know how activiti is able to handle this.

yes.

If the next task (Service Task) throws an exception on server B is Server A able to execute it again?

I assume that service task is asynchronous and jobexecutor is running on both instances A,B. (all code is available on A,B). then the answer is yes.

I hope this managed automatically by the process engine?

Yes, but you have to understand what is part of the transaction and what is not. (read doc)

Is this possible with activiti?

Yes. Read more bout wait states and transaction management in activiti source.

Regards
Martin

Re: Multi server environment

einszwo — Tue, 28 Apr 2015 10:23:37 GMT

Ok I read the documentation again and I think I understand the concepts.
Let me outline it:

I have an infrastructure with Server A and Server B with an embedded process engine pointing on the same database.

I have a simple process model (no parallel execution) with two Service Tasks (Service Task 1 and Service Task 2) which are configured with activiti:async="true" and activiti:exclusive="true".

I use the new Async executor.

When a process instance of the process model starts on server A, it is locked in DB and Service Task 1 ist executed. After execution the transaction ist committed an the process instance is unlocked.
In the next step maybe Server A or B tries to execute Service Task 2. Which one is not specified. For example it could be Server B which than locks the process instance again executes the task, commits the transaction and unlocks the process instance.

Than the process instance is finished.

If an exception occurs when executing a Service Task, the process instance will be unlocked and the job will be retried after configured time? (by some Server??? Or by the same server??)

Do I unterstand it the concepts right?

Re: Multi server environment

jbarrez — Tue, 28 Apr 2015 19:12:00 GMT

Yes, that is correct.

The time to wait is set in the config file of the server, and indeed can be different from server to server (if you really would want that).