Version selector strategy

When several versions of the same grain interface exist in the cluster and a new activation needs to be created, Orleans chooses a compatible version according to the strategy defined in GrainVersioningOptions.DefaultVersionSelectorStrategy.

Orleans supports the following strategies out of the box:

All compatible versions (default)

Using this strategy, Orleans chooses the version of the new activation randomly from all compatible versions.

For example, if you have two versions of a given grain interface, V1 and V2:

• V2 is backward compatible with V1.
• In the cluster, 2 silos support V2, and 8 support V1.
• The request was made from a V1 client/silo.

In this case, there's a 20% chance the new activation will be V2 and an 80% chance it will be V1.

Latest version

Using this strategy, the version of the new activation is always the latest compatible version. For example, if you have two versions of a given grain interface, V1 and V2 (where V2 is backward or fully compatible with V1), then all new activations will be V2.

Minimum version

Using this strategy, the version of the new activation is always the requested version or the minimum compatible version. For example, if you have two versions of a given grain interface, V2 and V3, both fully compatible:

• If the request was made from a V1 client/silo, the new activation will be V2.
• If the request was made from a V3 client/silo, the new activation will also be V2.