Dublin Server Clustering

Question

Hi

What will be the approach to load balanced clustering of servers under Dublin? Will workflow execution occur on multiple servers? I expect a workflow instance domain is limited to a single server but will new instances of the same workflow type (pattern) instantiate on other servers to scale?

Thanks

Greg

Answer 1

Greg,

You are right that the a workflow instance will execute on a single server and that new instance will instantiate on other servers in the farm.

Dublin will allow you to use any load-balancing mechanism and Dublin will start the new instances. If there are messages for an already created instance the persistence provider in Dublin will make sure that the correct instance is loaded from the DB.

Hope this helps,
George

Answer 2

Hi Following on from Gregs question just wondering what will happen in a scenario where the workflow has started and is in process.  It has been persisted but then the server it was executing on becomes unavailable for a period of time.

If the execution is limited to a single server does this mean the instance can not continue until the server becomes available again?

Answer 3

Execution is not limited to a single server in the typical scenario - usually workflows are not affinitized to any perticular server or host.

In the scenario you describe above, if the WF has been persisted and another message arrives for it, then the WF will be re-loaded to the server that the message arrived at.

If the WF was running and the server crashes for some reason, then the instance restart service will be able to bring the instance back up on another machine in the farm.