topic Re: Setting a custom IdGenerator in Alfresco Archive

Setting a custom IdGenerator

marcus1 — Thu, 15 Sep 2011 09:44:04 GMT

Activiti allows the user to configure a custom IdGenerator in ProcessEngineConfigurationImpl. This is useful for me since I want to use the adapted DbIdGenerator from http://jira.codehaus.org/browse/ACT-789. As I understand it these changes have not been applied to the Trunk since Tom felt it needed

Re: Setting a custom IdGenerator

jbarrez — Thu, 15 Sep 2011 13:43:15 GMT

Afaik, the custom id generator was added to trunk, just not enabled by default.

Re: Setting a custom IdGenerator

marcus1 — Thu, 15 Sep 2011 21:07:46 GMT

I only see two implementations of IdGenerator in Trunk: the default DbIdGenerator and StrongUuidGenerator. StrongUuidGenerator does not need a CommandExecutor.

Re: Setting a custom IdGenerator

ronald_van_kuij — Thu, 15 Sep 2011 22:34:41 GMT

The second one is the 'new' one…

Re: Setting a custom IdGenerator

marcus1 — Fri, 16 Sep 2011 07:13:44 GMT

I realize that StrongUuidGenerator is newer than DbIdGenerator

We experienced the same concurrency issues as described in this thread: http://forums.activiti.org/en/viewtopic.php?f=6&t=1521

The patch posted by Tom Baeyens in that thread (last post) seems to have fixed this issue for us. However, to be able to configure it (or any other custom IdGenerator which needs a CommandExecutor for i.e. database access), the changes I described are needed (AFAIK).

Re: Setting a custom IdGenerator

ronald_van_kuij — Fri, 16 Sep 2011 07:45:54 GMT

wasn't the concurrency issue caused by using a db id generator that needed db access? So wouldn't introducing a new/custom db id generator that requires this as wel have the same issues? Unless a separate connection is used for this… But then that is needed and not the command executor. Or do I mis something?

Re: Setting a custom IdGenerator

marcus1 — Fri, 16 Sep 2011 07:56:03 GMT

As I understand it the db connection was part of the problem, but that seems to have been solved in the adapted DbIdGenerator.

The generator uses a commandExecutorTxRequiresNew, and thus a separate connection (AFAIK):

if (idGenerator instanceof CommandExecutorAware) {
((CommandExecutorAware) idGenerator).setCommandExecutor(commandExecutorTxRequiresNew);
}

Re: Setting a custom IdGenerator

ronald_van_kuij — Fri, 16 Sep 2011 08:08:52 GMT

Sorry, I meant separate connection pool… The issue was that if all connections are busy doing functional db stuff, there is no connection anymore to retrieve a new id. But I could be wrong that that is solved by the change. If so, the need for the uuid db generator was superfluous.

Re: Setting a custom IdGenerator

marcus1 — Mon, 19 Sep 2011 14:34:24 GMT

Hmm… I'm now wondering why I haven't simply been using the StrongUuidGenerator… It seems to work fine after some quick tests.