Publishing gRPC services over REST/HTTP with gRPC Gateway

In the previous post we’ve seen how to implement a gRPC service in Scala. While gRPC is a great way to implement remote services, many client/server interactions are still implemented using REST/HTTP nowadays.

So the question is: Is it possible to use gRPC to define and implement services and make them available over REST at the same time?

Well, it turns out it’s possible. The translation from protobuf to JSON format is quite straightforward. The only thing left is to define associated endpoints for each of the gRPC calls. Here again it can be easily done along with the gRPC definition using the HTTP annotations from Google.

This is exactly what GRPC-Gateway provides. While GRPC-Gateway is implemented in Go it can run along with any gRPC implementation as it only relies on the protobuf/gRPC definitions (.proto files). It then spawns up an HTTP proxy that translates and forwards REST (HTTP/JSON) calls to a gRPC server.

Fortunately ScalaPB‘s code generation makes it possible to implement the same functionalities in Scala. Continue reading “Publishing gRPC services over REST/HTTP with gRPC Gateway”

gRPC in Scala

As many might think, gRPC doesn’t stand for “google Remote Procedure Call” but is a recursive acronym meaning “gRPC Remote Procedure Call”. I don’t know if you buy it but the truth is that is was originally developed by Google and then open-sourced.

If you’ve been in the IT for a while RPC doesn’t necessarily bring back happy memories. On the JVM it all started with RMI in the 90s. RMI was inspired by CORBA and suffered from a lack of interoperability as both the client and the server had to be implemented in Java. RMI was also particularly slow as Java serialisation is not a very efficient protocol.

Later in the 2000s came XML based RPC with XML-RPC and especially SOAP. Both of these formats address the interoperability as it no longer matters how the client/server are implemented. They only need to speak XML. However XML is still not an efficient protocol and communications remain slow.

SOAP provides an interesting definition language (WSDL – Web Service Definition Language) that can be used to generate service implementations.

gRPC addresses all these drawbacks. By default, it uses protobuf (Protocol buffers) for the service definitions and as its serialisation mechanism, which allows it to interoperate with many different languages while providing an efficient serialisation protocol. gRPC also takes advantage of HTTP/2 to add streaming capabilities.

gRPC generates all the boilerplate code for you, so that you only have to implement the business logic inside your services. It supports a number of different languages out of the box: C++, Java (Netty), Python, Go, Ruby, C#, Javascript (Node.JS), Android, Objective-C and PHP.

Unfortunately Scala is not in the list! … but we have scalaPB (and sbt-protoc) to save the day! Continue reading “gRPC in Scala”

Kafka concepts and common patterns

Many people see Kafka as a messaging system but in reality it’s more than that. It’s a distributed streaming platform. While it can be used as a traditional messaging platform it also means that it’s more complex.

In this post we’ll introduce the main concepts present in Kafka and see how they can be used to build different application from the traditional publish/subscribe all the way up to streaming applications. Continue reading “Kafka concepts and common patterns”