In order to be able to better use the advantages of the Java alternative Kotlin such as expressiveness, security and support for writing asynchronous code with coroutines for its internal gRPC infrastructure especially for Android and cloud development, Google implemented the implementation gRPC Kotlin built – and released as open source in April 2020. Now the RPC framework has reached the first major version and is being launched with revised documentation, numerous bug fixes and expanded platform support.

Version 1.0 of gRPC Kotlin not only benefits from Kotlin’s coroutines for reactive input / output when creating data transmission objects and the services surrounding them, but also uses the Flow API to process streams with reactive input / output. In order to optimize the generated code for Android clients in particular, gRPC Kotlin uses the lite mode of gRPC Java: It enables Protobuf compilers to generate smaller, more powerful classes. The artifact grpc-kotlin-stub-lite depends on the associated grpc-protobuf-lite from. The generated Kotlin stub client can be used in the same way as on the JVM.

It also works without a JVM The Lite mode also allows the use of GraalVM Native Image, so that developers can create applications that compiled from Ahead-of-time (AOT) without a JVM native images run out. This enables smaller applications to be built that require less memory and are therefore also suitable for environments with limited resources. An example project shows how a native client application can be created with an only 14 MByte executable that, according to Google, starts in a split second, Kontakt records to the server, makes a request and processes the response.

The gRPC (google / general-purpose Remote Procedure Call) developed by Google is an open source framework for calling up functions in distributed computer systems and is primarily used by developers for communication between microservices. It uses the HTTP / 2 protocol for bidirectional streaming and protocol buffers as Interface Definition Language (IDL) or as the underlying message exchange format.

gRPC is primarily aimed at web and Android applications, but works in principle cross-platform and is available for a number of programming languages ​​- including Java, C ++, Go, Python and Ruby. The gRPC released as Open Source by Google 2015 has since proven itself as an “incubating project” at the Cloud Native Computing Foundation (CNCF).

Google sees the advantages of gRPC Kotlin not only on the client side, but also uses the RPC Framework also for backend services. With gRPC Kotlin, these applications should be particularly easy to package and make available in containerized form wherever Docker containers or JVM apps can be run – for example in Kubernetes clusters. However, Google is also targeting its own serverless computing service called Cloud Run, which was officially launched a year ago and promises a fully managed infrastructure for application operations.

Further information on version 1.0 of gRPC Kotlin can be found in the blog post about the publication of the major release as well as on the GitHub pages of the project.

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