topic Re: Boundary Timer event - couldn't instantiate class in Alfresco Archive

Boundary Timer event - couldn't instantiate class

satramalin — Wed, 16 Jul 2014 16:34:34 GMT

We have a scenario where we have a service task(Polling task) which polls a mailbox at constant intervals. We have to enable the polling through timers.We tried the following scenarios and ended up with 'Couldn't instantiate class' error.- We have the service task and then an user task with a bounda

Re: Boundary Timer event - couldn't instantiate class

martin_grofcik — Thu, 17 Jul 2014 07:48:04 GMT

Hi,

What was the reason for 'Couldn't instantiate class' error?

I would use cycleTimer or multiinstance task for this case .

Regards
Martin

Re: Boundary Timer event - couldn't instantiate class

satramalin — Thu, 24 Jul 2014 20:59:00 GMT

Hi Martin,
Thanks for the response. We found the issue. It was because of 2 process engines running on same database and both process engines were picking up the timers randomly. Say, Appln A picked the timer for Appln B and executed it. Is there any way to prevent this in a common database?

Re: Boundary Timer event - couldn't instantiate class

frederikherema1 — Fri, 25 Jul 2014 08:00:08 GMT

You can only use one node that executes jobs (disable job executor on second engine). This way, only one instance will pick up the jobs. This requires the job-executor engine to have all needed classes on the class path.

However, your question raises a red flag in my head. The same can happen when executing a process, not by the job-executor (eg. completing a task on engine 1 when it needs classes, present on engine 2). Either use 2 different databases or make your service-logic smart enough to only use processes that are guaranteed to work on the engine instance the API-call is done to…

Re: Boundary Timer event - couldn't instantiate class

satramalin — Fri, 25 Jul 2014 21:29:42 GMT

Thanks for your response. Please let me understand this issue. Now we have a plan of running 4 different applications with Activiti workflow on different application servers to use common Activiti tables in a shared database. Is your question (the same can happen when executing a process, not by the job-executor?) related to this scenario? In this case, if I understand correctly Appln A may consume not just the timers for Appln B but also the tasks. Please let me understand the risk in this architecture?

Re: Boundary Timer event - couldn't instantiate class

frederikherema1 — Tue, 29 Jul 2014 08:05:00 GMT

Timers are all stored in the ACT_RU_JOB table, to ensure no jobs are lost when the JVM goes down, for example. Any job-executor in any engine can lock/aquire a job from that table and start executing it.

So if you have 4 different apps running against the same database, jobs for app A could be execute on B, C or D's engine and visa-versa. Having this architecture is bound to get you in trouble (not only job-related). Any specific need to have all data in the same tables? If you want to have it all in the same schema/database, you can always use a table name prefix for each of the apps (eg. job table will be APP1_ACT_RU_JOB for app 1).

The prefix can be configured in the processEngineConfiguration, but table creation needs to be done manually, as the db-scripts we have contain the non-prefixed version. It's a matter of doing a search/replace on all the db-create-scripts…