In gRPC a client application can directly call methods on a server application on a different machine as if it was a local object, making it easier for you to create distributed applications and services. As in many RPC systems, gRPC is based around the idea of defining a service, specifying the methods that can be called remotely with their parameters and return types. On the server side, the server implements this interface and runs a gRPC server to handle client calls. On the client side, the client has a stub (referred to as just a client in some languages) that provides the same methods as the server.
gRPC clients and servers can run and talk to each other in a variety of environments – from servers inside Google to your own desktop – and can be written in any of gRPC’s supported languages. So, for example, you can easily create a gRPC server in Java with clients in Go, Python, or Ruby. In addition, the latest Google APIs will have gRPC versions of their interfaces, letting you easily build Google functionality into your applications.
Working with Protocol Buffers
By default gRPC uses protocol buffers, Google’s mature open source mechanism for serializing structured data (although it can be used with other data formats such as JSON).
gRPC is used in last mile of computing in mobile and web client since it can generate libraries for iOS and Android and uses standards based HTTP/2 as transport allowing it to easily traverse proxies and firewalls. There is also work underway to develop a JS library for use in browsers. Beyond that, it is ideal as a microservices interconnect, not just because the core protocol is very efficient but also because the framework has pluggable authentication, load balancing etc. Google itself is also transitioning to use it to connect microservices.