Changing number of partitions for a reliable actor service

Question

When I create a new Service Fabric actor the underlying (auto generated) actor service is configured to use 10 partitions.

I'm wondering how much I need to care about this value?

In particular, I wonder whether the Actor Runtime has support for changing the number of partitions of an actor service on a running cluster.

The Partition Service Fabric reliable services topic says:

In rare cases, you may end up needing more partitions than you have initially chosen. As you cannot change the partition count after the fact, you would need to apply some advanced partition approaches, such as creating a new service instance of the same service type. You would also need to implement some client-side logic that routes the requests to the correct service instance, based on client-side knowledge that your client code must maintain.

However, due to the nature of Actors and that they are managed by the Actor Runtime I'm tempted to believe that it would indeed be possible to do this. -- That the Actor Runtime would be able to take care of all the heavylifting required to re-partition actor instances.

Is that at all possible?

Answer 1

The number of partitions in a running service cannot be changed. This is true of Actors as well as Reliable Services. Typically, you would want to pick a large number of partitions (more than the number of nodes) up front and then scale out the number of nodes in the cluster instead of trying to repartition your data on the fly. Take a look at Abhishek and Matthew's comments in the discussion here for some ideas on how to estimate how many partitions you might need.