Version selector strategy

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

Orleans out of the box supports the following strategies:

All compatible versions (default)

Using this strategy, the version of the new activation will be chosen randomly across all compatible versions.

For example, if we have 2 versions of a given grain interface, V1 and V2:

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

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

Latest version

Using this strategy, the version of the new activation will always be the latest compatible version. For example, if we have 2 versions of a given grain interface, V1 and V2 (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 will always be the requested or the minimum compatible version. For example, if we have 2 versions of a given grain interface, V2, V3, all fully compatibles:

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