readme.md

readme

This example builds on top of Solution 3 by introducing IPersistentState to grains. The goal for this example is to demonstrate how to persist grain's state into a storage provider, in this case DynamoDB.

how it works

• state is injected as IPersistentState<HelloWorldState> where HelloWorldState is a simple serializable POCO.
• state is not loaded at grain construction time, but before OnActivateAsync is called.
• ISiloBuilder is configured with DynamoDB properties. In my case, I have the following:
  • AWS_SECRET_ACCESS_KEY
  • AWS_SESSION_TOKEN
  • AWS_ACCESS_KEY_ID values set as my environment variables, so the silo configuration gets reduced to this:

    siloBuilder.AddDynamoDBGrainStorage(
      name: "helloWorldStore",
      configureOptions: options =>
      {
          options.UseJson = true;
          options.Service = "us-west-2";
      });

• AddDynamoDBGrainStorage defaults the table to be OrleansGrainState if the value is not provided.

More on grain persistence here: https://dotnet.github.io/orleans/docs/grains/grain_persistence/index.html

running the code

The code can be ran using the same type of scripts as the previous examples. Upon calling the grain, it greets the caller and displays the current time persisting it at the same to its state which in turn gets saved to DynamoDB.

Here is how the saved state looks like when saved from:

• grain identified by 0:

  

  {
    "GrainReference": "_GrainReference=000000000000000000000000000000000300000002293d31",
    "GrainType": "Grains.HelloWorld,Grains.helloWorldState",
    "ETag": 3,
    "StringState": "{\"$id\":\"1\",\"$type\":\"Grains.HelloWorldState, Grains\",\"GreetingTimeUtc\":\"2021-02-19T00:01:44.128848Z\"}"
  }

• grain identified by 1:

  {
   "GrainReference": "_GrainReference=000000000000000000000000000000010300000002293d31",
   "GrainType": "Grains.HelloWorld,Grains.helloWorldState",
   "ETag": 0,
   "StringState": "{\"$id\":\"1\",\"$type\":\"Grains.HelloWorldState, Grains\",\"GreetingTimeUtc\":\"2021-02-19T09:34:15.2662484Z\"}"
  }

• grain identified by 2:

  {
    "GrainReference": "_GrainReference=000000000000000000000000000000020300000002293d31",
    "GrainType": "Grains.HelloWorld,Grains.helloWorldState",
    "ETag": 0,
    "StringState": "{\"$id\":\"1\",\"$type\":\"Grains.HelloWorldState, Grains\",\"GreetingTimeUtc\":\"2021-02-19T00:09:41.28897Z\"}"
  }

I called three different grains from the client (grain ids 0, 1 and 2) and this is how my DynamoDB table looks like: