Migrating to AKKA 2.6 Typed

I'm starting to migrate a few projects to AKKA 2.6 from AKKA 2.*. The idea is to start using the new (and looks like now more mature) Akka Typed.

So I will use this repo to try the migration in a small project before to go ahead with the others.

So the current state of this project covers:

• Akka gRPC
• Akka Classic + Typed
• Akka Event Sourcing
• Akka Persistence

Parts that took more time:

• Move from Akka Classic to Akka Typed.
• Integration of Akka gRPC and Akka Typed.

Services description

Remind that the idea of this service is not to implement something cool but something to prove how to migrate and the differences between Classic and Typed style.

So the functionality is really simple. It is a Counter service. It is going to keep the counter in the service along with the number of events created. The client will stimulate the counter.

So this is the list of services to expose:

• Inc will increment the counter the X times and increment one time the events counter.
• Incs like Inc service but in a streaming way.
• Get will return the counter and the number of events generated.

The definition is in the submodule protobuf-api

Design

The project is organized on the way to be able to compare Classic and Typed implementation. To do it, I implemented both cases and I used the suffix *Classic and *Typed in all files.

Running

From the project root:

sbt clean universal:packageZipTarball

Inside of every target/universal submodule you will find a tgz file with all necessary to run the app.

Server side

The server is using typesafe config configuration system, so it is possible to override all configuration:

• server.style = classic or typed. Default typed
• server.interface = interface binding. Default 0.0.0.0 so listening from everywhere.
• server.port = Port listening. Default 8080

Running setting, for example, the server interface to listen:

bin/server -Dserver.interface=localhost

Client side

The implementation is using the Akka gRPC like the server, so it is using typesafe config configuration system.

• akka.grpc.client.example.api.CounterService.host = Server host. Default locahost
• akka.grpc.client.example.api.CounterService.port = Server port. Default 8080

Three different behaviors depending on the number of parameters:

• No parameters: Return the counter and the number of events generated.
• One parameter: Increment the counter X times.
• Two parameters: Execute the previous one as a stream, calling the service one time every value in the range.

Increment 10 with defaults

bin/client 10

Example:

In on terminal, execute the server:

$ bin/server
[2019-11-16 17:14:23,252] [INFO] [akka.event.slf4j.Slf4jLogger] [CounterServer-akka.actor.default-dispatcher-6] [] - Slf4jLogger started
[2019-11-16 17:14:23,366] [WARN] [akka.persistence.Persistence] [CounterServer-akka.actor.default-dispatcher-9] [Persistence(akka://CounterServer)] - No default snapshot store configured! To configure a default snapshot-store plugin set the `akka.persistence.snapshot-store.plugin` key. For details see 'reference.conf'
Counter server typed online at http://0:0:0:0:0:0:0:0:8080/

In other terminal, execute the client:

$ bin/client
Current state: Accumulator [0] / Events executed [0].

$ bin/client 10
Successfully incremented.

$ bin/client
Current state: Accumulator [10] / Events executed [1].

$ bin/client 5 10
Incremented Done()
Incremented Done()
Incremented Done()
Incremented Done()
Incremented Done()
Incremented Done()
Incremented range [Range 5 to 10].

$ bin/client
Current state: Accumulator [55] / Events executed [7].

Future

In the future, I will use this project to do add:

• Clustering
• Sharding