Service fabric actor state and list

问题

Is it recommended to have a list in Service fabric actor? I am trying to keep User favorites in a User Actor. What is best approach for this scenario?

回答1:

Yes, as long as you treat the list as immutable.

The state manager retrieval methods return a reference to an object in local memory. Modifying this object in local memory alone does not cause it to be saved durably. When an object is retrieved from the state manager and modified, it must be reinserted into the state manager to be saved durably.

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The UserInfo type below demonstrates how to define an immutable type taking advantage of aforementioned recommendations.

[DataContract]
// If you don’t seal, you must ensure that any derived classes are also immutable
public sealed class UserInfo {
   private static readonly IEnumerable<ItemId> NoBids = ImmutableList<ItemId>.Empty;

   public UserInfo(String email, IEnumerable<ItemId> itemsBidding = null) {
      Email = email;
      ItemsBidding = (itemsBidding == null) ? NoBids : itemsBidding.ToImmutableList();
   }

   [OnDeserialized]
   private void OnDeserialized(StreamingContext context) {
      // Convert the deserialized collection to an immutable collection
      ItemsBidding = ItemsBidding.ToImmutableList();
   }

   [DataMember]
   public readonly String Email;

   // Ideally, this would be a readonly field but it can't be because OnDeserialized
   // has to set it. So instead, the getter is public and the setter is private.
   [DataMember]
   public IEnumerable<ItemId> ItemsBidding { get; private set; }

   // Since each UserInfo object is immutable, we add a new ItemId to the ItemsBidding
   // collection by creating a new immutable UserInfo object with the added ItemId.
   public UserInfo AddItemBidding(ItemId itemId) {
      return new UserInfo(Email, ((ImmutableList<ItemId>)ItemsBidding).Add(itemId));
   }
}

more info: 1 and 2

来源：https://stackoverflow.com/questions/46414438/service-fabric-actor-state-and-list