Created
December 26, 2016 21:00
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JournaledGrain + SS
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| /* | |
| https://github.com/dotnet/orleans/blob/master/src/OrleansEventSourcing/JournaledGrainState.cs | |
| The example from Orleans repo uses existing providers to store the event stream as List<Event>. | |
| This is not needed when using StreamStone - instead of using existing providers and calling WriteStateAsync() you can read / write yourself | |
| */ | |
| // 1. Define class that will be used by StreamStone to represent event row | |
| public class EventEntity : TableEntity | |
| { | |
| public Guid Id { get; set; } | |
| public string Type { get; set; } | |
| public string Data { get; set; } | |
| public string Metadata { get; set; } | |
| public int Version { get; set; } // Azure doesn't support uint :-( | |
| } | |
| // 2. Grain using SS | |
| public class EventSourcedGrain<TState> : JournaledGrain<TState> | |
| where TState : JournaledGrainsState | |
| { | |
| public override async Task OnActivate() | |
| { | |
| try | |
| { | |
| StreamSlice<EventEntity> slice; | |
| var nextSliceStart = 1; | |
| do | |
| { | |
| slice = await Stream.ReadAsync<EventEntity>(this.Partition, nextSliceStart, sliceSize: 1); | |
| foreach (var eventData in slice.Events) | |
| { | |
| dynamic @event = JsonConvert.DeserializeObject(eventData.Data, Type.GetType(eventData.Type)); | |
| this.State.StateTransition(@event); // Make this method public | |
| this.Version++; | |
| } | |
| nextSliceStart = slice.HasEvents ? slice.Events.Last().Version + 1 : -1; | |
| } | |
| while (!slice.IsEndOfStream); | |
| } | |
| catch (StreamDoesNotExistException) | |
| { | |
| } | |
| await base.OnActivate(); | |
| } | |
| protected ovrride async Task WriteStateAsync() | |
| { | |
| var events = this.State.Events; | |
| await Stream.WriteAsync(this.Partition, this.Version, events); // Serialiaze events from State and write them using SS | |
| this.State.Clear(); // Clear internal List<Event> | |
| } | |
| } |
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