API gateway/proxy pattern for microservices deployed using Azure Service Fabric
This feature is build in for http endpoints, starting with release 5.0 of service fabric. The documentation is available at https://azure.microsoft.com/en-us/documentation/articles/service-fabric-reverseproxy/
The service registration/discoverability you need to do this is actually already there. There's a stateful system service called the Naming Service, which is basically a registrar of service instances and the endpoints they're listening on. So when you start up a service - either stateless or stateful - and open some listener on it, the address gets registered with the Naming Service.
Now the part you'd need to fill in is the "gateway" that users interact with. This doesn't have to be stateful because the Naming Service manages the stateful part. But you'd have to come up with an addressing scheme that works for you, and then it would just forward requests along to the right place. Basically something like this:
- Receive request.
- Use NS to find the service that can take the request.
- Forward the request to it and the response back to the user.
- If the service doesn't exist anymore, 404.
In general we don't like to dictate anything about how your services talk to each other, but we are thinking of ways to solve this problem for HTTP as a complete built-in solution.
We implemented a HTTP gateway service for this purpose as well. To make sure we can have one HTTP gateway for any internal protocol, we implemented the gateway for HTTP based internal services (like ASP.NET WebAPIs) using an ASP.NET 5 middleware. It routes requests from e.g /service to an internal Service Fabric address like fabric:/myapp/myservice by using the ServicePartitionClient and some retry logic from CommunicationClientFactoryBase.
We open-sourced this middleware and you can find it here: https://github.com/c3-ls/ServiceFabric-HttpServiceGateway
There's also some more documentation in the wiki of the project.