This sample shows a client/server scenario using saga persistence.
Prerequisites
This sample uses a DynamoDB local instance by default. See the AWS guidance on deploying DynamoDB local.
Alternatively with Docker installed locally, execute the following command in the solution directory:
docker-compose up -d
the data is only kept in memory and will be gone when the container is removed.
Projects
Client
- Sends the
StartOrdermessage toServer. - Receives and handles the
OrderCompletedevent.
Server projects
- Receive the
StartOrdermessage and initiate anOrderSaga. OrderSagarequests a timeout with an instance ofCompleteOrderwith the saga data.OrderSagapublishes anOrderCompletedevent when theCompleteOrdertimeout fires.
SharedMessages
Contains the shared message contracts used by all endpoints.
Persistence config
Configure the endpoint to use DynamoDB Persistence.
var amazonDynamoDbClient = new AmazonDynamoDBClient(
new BasicAWSCredentials("localdb", "localdb"),
new AmazonDynamoDBConfig
{
ServiceURL = "http://localhost:8000"
});
var endpointConfiguration = new EndpointConfiguration("Samples.DynamoDB.Simple.Server");
var persistence = endpointConfiguration.UsePersistence<DynamoPersistence>();
persistence.DynamoClient(amazonDynamoDbClient);
persistence.UseSharedTable(new TableConfiguration
{
TableName = "Samples.DynamoDB.Simple"
});
Order saga data
public class OrderSagaData :
ContainSagaData
{
public Guid OrderId { get; set; }
public string OrderDescription { get; set; }
}
Order saga
public class OrderSaga :
Saga<OrderSagaData>,
IAmStartedByMessages<StartOrder>,
IHandleTimeouts<CompleteOrder>
{
static ILog log = LogManager.GetLogger<OrderSaga>();
protected override void ConfigureHowToFindSaga(SagaPropertyMapper<OrderSagaData> mapper)
{
mapper.MapSaga(saga => saga.OrderId).ToMessage<StartOrder>(msg => msg.OrderId);
}
public Task Handle(StartOrder message, IMessageHandlerContext context)
{
var orderDescription = $"The saga for order {message.OrderId}";
Data.OrderDescription = orderDescription;
log.Info($"Received StartOrder message {Data.OrderId}. Starting Saga");
var shipOrder = new ShipOrder
{
OrderId = message.OrderId
};
log.Info("Order will complete in 5 seconds");
var timeoutData = new CompleteOrder
{
OrderDescription = orderDescription,
};
return Task.WhenAll(
context.SendLocal(shipOrder),
RequestTimeout(context, TimeSpan.FromSeconds(5), timeoutData)
);
}
public Task Timeout(CompleteOrder state, IMessageHandlerContext context)
{
log.Info($"Saga with OrderId {Data.OrderId} completed");
MarkAsComplete();
var orderCompleted = new OrderCompleted
{
OrderId = Data.OrderId
};
return context.Publish(orderCompleted);
}
}