gRPC From Python To Python

Click into the numbered directories for all the details and code.

The goal here is to write some code using gRPC, Python and Golang.

Overview of gRPC

resource: Below are some quick take aways from gRPC Docs on gRPC Concepts.

Service

• gRPC defines a service. This service could be written in Python. gRPC makes the Python methods available to be called by either C++, Java (incl. support for Android), Objective-C (for iOS), Python, Ruby, Go, C# and Node.js
• gRPC uses protocol buffers as the IDL (Interface Development Language)

Defining the API

• .proto file is used to define a service. Once a proto file is compiled it'll generate server and client side code. Using the generated code:
  • The server implements the methods declared by the service.
  • The client has access to call the same methods as the service.
• gRPC is both synchronous and asyncronous.
• gRPC is written on top of HTTP/2

RPC request cycle

• Unary RPC
  • client sends one message and receives a single response from the server.
• Streaming
  • Server Streaming
    • client sends one message and receives a stream of messages from the server.
  • Client Streaming
    • client sends a stream of messages, waits and receives a single response from the server.
  • Bidirectional Streaming
    • client and server stream messages back and forth.
    • Neither have to wait for messages to complete before responding.
    • Client and server could both send messages asynchronously.
• Cancelling RPCs
  • Deadlines/Timeouts
    • could be set by both client and server.
  • Termination
    • the client and server make independent and local determinations of whether a call was successful.
• Metadata
  • each request comes with metadata information about the request success or failure.
  • list of key-value pairs
• Channels
  • connection to a gRPC server on a specified host and port
  • used when creating a client stub (or just “client” in some languages)

Architecture of gRPC

resource: Is gRPC the Future of Client-Server Communication?

1. Transport:
   • HTTP/2 is gRPC's transport.
2. Channel:
   • Client connection to a server
3. Stub:
   • generated by compiling the .proto file.
   • provides API methods as they're written