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Why gRPC

  • Today's trend is to build micro services. For these services to communicate with each other we need APIs.
  • Standard approach is to build REST APIs. But it comes with a lot of problems. Like:

    • You need to think about the endpoint.
    • You need to think about how to invoke the API and how to handle errors.
    • You need to have a retry mechanism in case of failures.
    • You need to think about efficiency, latency, interoperability etc,
    • You need to think about logging, authentication etc.
    • Now if there are multiple micro services all these need be done for all the micro services.
  • gRPC aims to solve all the above problems by abstracting it from us and standardising the communication between services.

What is RPC

  • An RPC is a Remote Procedure Call.
  • It is designed to make a network call look just like a function call. It does this by abstracting all the complexities like serialisation, deserialisation and transport.
  • In your CLIENT code, it looks like you're just calling a function directly on the SERVER.

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  • RPC is not a new concept but in gRPC it has been implemented cleanly and solves a lot of problems.

  • There are different RPC implementations but the most famous is gRPC.


  • In RPC data is serialised/deserialised. Stub is responsible for serialisation and deserialisation.
  • In the example given below Golang's struct is first serialised to be sent over network and then deserialised to be converted to Java's class. All this is done by stub.
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    • So in short a stub converts methods, request types, and response types into a form used by the RPC system.
Stub is the main reason why RPCs appear to be like local function calls.
  • gRPC uses protobuf format to define stubs. The extension of the file is .proto
  • .proto file is also known as stub interface definition.
  • Stub generator generates the code for us.

Communication in RPC

  • RPC can use any layer 3 protocol TCP or UDP.
  • RPC can also happen over HTTP.
  • For example gRPC uses HTTP 2 for its transport layer.
  • You can also write your own RPC implementation and use websockets for communication.

What is serialisation and deserialisation

  • Data serialisation is the process of converting an object into a stream of bytes to more easily save or transmit it.
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  • Serialisation and deserialisation work together to transform/recreate data objects to/from a portable format.
  • The verbs Marshal and Unmarshal are synonymous with serialise and deserialise
  • Serialising takes complex data and lists it in a sequential manner. This is what pickle (python library for writing to files) does under the hood.

Serialisation formats

  • Some serialisation formats are:
    • JSON: serialised to plain text. In JavaScript, for example, you can serialise an object to a JSON string by calling the function JSON.stringify().
    • Protobuf: serialised to binary.
    • XML
JSON vs Protobuf
  • Like JSON Protobuf is also a message format.
  • JSON is great when you have small volume of message exchange where as protobuf is great when you have a high volume of message exchange.
  • Protobuf is something you would use if performance really matters.

What is gRPC

  • It is a free and open source framework developed by google. It is now a part of CNCF (Cloud Native Computing Foundation) like Kubernetes and Prometheus.
  • At a high level, it allows you to define REQUEST and RESPONSE for RPC (Remote Procedure Calls) and handles all the rest for you.
  • On top of it, it's modern, fast and efficient, build on top of HTTP/2 (implementation is abstracted from us), low latency, supports streaming, language independent, and makes it super easy to plug in authentication, load balancing, logging and monitoring.
  • It is best for building micro services.
  • At the core of gRPC, you need to define the messages and services using Protocol Buffers
  • The rest of the gRPC code will be generated for you and you'll have to provide an implementation for it.
  • One .proto file works for over 12 programming languages (server and client), and allows you to use a framework that scales to millions of RPC per seconds.
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Last updated: 2022-05-17