gRPC (gRPC Remote Procedure Call) - CLIENT

High-performance, open-source Remote Procedure Call (RPC) framework originally developed by Google.
It allows an application to directly call a method on a server application located on a different machine as if it were a local object,
making it a popular choice for microservices architectures. https://grpc.io/

How gRPC Works

• Protocol Buffers (Protobuf):
  Instead of text-based formats like JSON, gRPC uses Protobuf (a binary serialization format) to define the API and serialize structured data.
  Payload sizes significantly smaller and parsing much faster. https://protobuf.dev/
• HTTP/2 Transport:
  Uses HTTP/2. Enabling multiplexing (multiple requests on a single connection), header compression, and full bidirectional streaming.
• Contract-First Development:
  
  • Define the API structure, methods, and data types in a .proto file.
  • gRPC compiler automatically generates strongly-typed client and server code. supported languages

GET WEATHER Via gRPC

• This is a C# API WeatherApi - client (with this static HTML page at the root)
• Hosted on Azure at: grpc-weather-client-hhfmhrbhemavfte3.uksouth-01.azurewebsites.net (Windows OS)
• The WeatherApi - client endpoint calls a WeatherService - server via gRPC
• WeatherService - server hosted at: https://container-app-weather.thankfultree-2d5a04b9.uksouth.azurecontainerapps.io/ (in a Container App)
• Both WeatherApi - client and WeatherService - server built & deployed from AzureDevOps at: https://dev.azure.com/jones-steve/GprcWeather/_build
• Both WeatherApi - client and WeatherService - server in a repo at : https://github.com/wizzard262/weather-via-grpc
• The WeatherService - server calls the FREE (no auth, key, tokens, signup) weather API https://open-meteo.com/
  with a path like https://api.open-meteo.com/v1/forecast?latitude=53.41&longitude=-2.15¤t=temperature_2m,weather_code
  Note: This returns 2 data items we will use:
  • Current temperature: temperature_2m
  • Weather Code: weather_code
    (Note: this number corresponds to a lookup. Go to: https://open-meteo.com/en/docs#weathervariables and search for:" WMO Weather interpretation codes")
• The WeatherService - server responds to the WeatherApi - client via gRPC
• The WeatherApi - client deserializes the gRPC message and displays the weather result (see form below)
• Note: The returned JSON data also includes the raw_protobuf for reference.
• The proto contract weather.proto is used by both the client and the server
  It auto-generates C# code (or whatever other supported language the service might be written in)
  It defines:
  • Proto Schema Language version: syntax = "proto3";
  • Data contract: WeatherRequest and WeatherResponse define the exact fields, types, and field numbers used for exchanging data between client and server.
  • Service contract: WeatherService with its GetWeather RPC defines the API interface:
    • Method name GetWeather
    • Request type WeatherRequest
    • Response type WeatherResponse
  • Wire contract: The field numbers (= 1, = 2) and types (double, string) define the binary Protobuf wire format, ensuring compatibility across languages and versions.

Protobuf Hex Deserializer

Paste the raw_protobuf value from "GetWeather" (see above) to see the hexadecimal (i.e. binary) Protobuf message deserialized into the WeatherResponse

Draw.io Diagram

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