v4 and MongoDB saga/statemachine persistence

[Nick Archibald]

Hi Guys

I am trying to get a Saga/statemachine working with MongoDB Persistence. I currently have it working where the initail event is persisted but I get the following exception when receiving other messages that should match to the initial one.

System.FormatException: Element '_id' does not match any field or property of class CmeConnect.LimeSurvey.Common.Sagas.States.HookBatchState.

   at MongoDB.Bson.Serialization.BsonClassMapSerializer`1.DeserializeClass(BsonDeserializationContext context)

   at MongoDB.Bson.Serialization.BsonClassMapSerializer`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)

   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)

   at MongoDB.Driver.Core.Operations.CursorBatchDeserializationHelper.DeserializeBatch[TDocument](RawBsonArray batch, IBsonSerializer`1 documentSerializer, MessageEncoderSettings messageEncoderSettings)

   at MongoDB.Driver.Core.Operations.FindCommandOperation`1.CreateCursorBatch(BsonDocument commandResult)

   at MongoDB.Driver.Core.Operations.FindCommandOperation`1.CreateCursor(IChannelSourceHandle channelSource, BsonDocument commandResult, Boolean slaveOk)

   at MongoDB.Driver.Core.Operations.FindCommandOperation`1.<ExecuteAsync>d__111.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

I think it might be with my correlation setup but it looks correct when comparing with the ShoppingCart example. Does the exception ring anyone's bell?

Is there a example anyone can link me that using MongoDB persistence for a sag?

Thanks

Nick

[Nick Archibald]

OK I worked this one out.

The exception is occurring because it can't serialize the '_id'  field into the class object I have. However the '_id' value should have been the CorrelationId. So to help the serializer out I added the [BsonElement("_id")] to the CorrelationId property. This tells the serialize to map the CorrelationId to the MongoDB's _id field. So what you see in MongoDB is no CorrelationId property on the document but the _id field is containing this value.

Maybe this might help someone or someone can tell me whether there is a better way.

[Chris Patterson]

This is what I use in the unit tests:

https://github.com/MassTransit/MassTransit/blob/develop/src/Persistence/MassTransit.MongoDbIntegration.Tests/Saga/Data/SimpleSaga.cs#L34

[BsonId]

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