akka-grpc

Support for building streaming gRPC servers and clients on top of Akka Streams.

This library is meant to be used as a building block in projects using the Akka toolkit.

Documentation

Akka gRPC reference documentation

Project Status

This library is ready to be used in production, but API's and build system plugins are still expected to be improved and may change.

The API on both sides (Client and Server) is a simple Akka Streams-based one. We plan to also provide a 'power user' API for each of these (#191, #179).

The client side is currently implemented on top of io.grpc:grpc-netty-shaded, we plan to replace this by io.grpc:grpc-core and Akka HTTP.

As for performance, we are currently relying on the JVM TLS implementation, which is sufficient for many use cases, but is planned to be replaced with conscrypt or netty-tcnative.

General overview

gRPC is a schema-first RPC framework, where your protocol is declared in a protobuf definition, and requests and responses will be streamed over an HTTP/2 connection.

Based on a protobuf service definition, akka-grpc can generate:

Model classes (using plain protoc for Java or scalapb for Scala)
The API (as an interface for Java or a trait for Scala), expressed in Akka Streams Sources
On the server side, code to create an Akka HTTP route based on your implementation of the API
On the client side, a client for the API.

Project structure

The project is split up in a number of subprojects:

codegen: code generation shared among plugins
runtime: run-time utilities used by the generated code
sbt-plugin: the sbt plugin
scalapb-protoc-plugin: the scalapb Scala model code generation packaged as a protoc plugin, to be used from gradle
interop-tests: test interoperability between the Akka implementation and the implementation from io.gpc:grpc-interop-testing, based on gRPC's original testset. These tests are duplicated as more faithful 'scripted' tests under the sbt-project module.

Additionally, 'plugin-tester-java' and 'plugin-tester-scala' contain an example project in Java and Scala respectively, with both sbt and Gradle configurations.

Compatibility & support

This project does not yet have to obey the rule of staying binary compatible between releases that is common for Akka libraries. Breaking API changes may be introduced without notice as we refine and simplify based on your feedback.

If used with JDK 8 you must add an ALPN agent.