go-micro/README.md

# Go Micro [![Go.Dev reference](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white&style=flat-square)](https://pkg.go.dev/go-micro.dev/v5?tab=doc) [![Go Report Card](https://goreportcard.com/badge/github.com/go-micro/go-micro)](https://goreportcard.com/report/github.com/go-micro/go-micro)

Go Micro is a framework for distributed systems development.

## Overview

Go Micro provides the core requirements for distributed systems development including RPC and Event driven communication.
The Go Micro philosophy is sane defaults with a pluggable architecture. We provide defaults to get you started quickly
but everything can be easily swapped out.

## Features

Go Micro abstracts away the details of distributed systems. Here are the main features.

- **Authentication** - Auth is built in as a first class citizen. Authentication and authorization enable secure
  zero trust networking by providing every service an identity and certificates. This additionally includes rule
  based access control.

- **Dynamic Config** - Load and hot reload dynamic config from anywhere. The config interface provides a way to load application
  level config from any source such as env vars, file, etcd. You can merge the sources and even define fallbacks.

- **Data Storage** - A simple data store interface to read, write and delete records. It includes support for many storage backends
in the plugins repo. State and persistence becomes a core requirement beyond prototyping and Micro looks to build that into the framework.

- **Service Discovery** - Automatic service registration and name resolution. Service discovery is at the core of micro service
  development. When service A needs to speak to service B it needs the location of that service. The default discovery mechanism is
  multicast DNS (mdns), a zeroconf system.

- **Load Balancing** - Client side load balancing built on service discovery. Once we have the addresses of any number of instances
  of a service we now need a way to decide which node to route to. We use random hashed load balancing to provide even distribution
  across the services and retry a different node if there's a problem.

- **Message Encoding** - Dynamic message encoding based on content-type. The client and server will use codecs along with content-type
  to seamlessly encode and decode Go types for you. Any variety of messages could be encoded and sent from different clients. The client
  and server handle this by default. This includes protobuf and json by default.

- **RPC Client/Server** - RPC based request/response with support for bidirectional streaming. We provide an abstraction for synchronous
  communication. A request made to a service will be automatically resolved, load balanced, dialled and streamed.

- **Async Messaging** - PubSub is built in as a first class citizen for asynchronous communication and event driven architectures.
  Event notifications are a core pattern in micro service development. The default messaging system is a HTTP event message broker.

- **Pluggable Interfaces** - Go Micro makes use of Go interfaces for each distributed system abstraction. Because of this these interfaces
  are pluggable and allows Go Micro to be runtime agnostic. You can plugin any underlying technology.

## Getting Started

To make use of Go Micro import it 

```golang
import "go-micro.dev/v5"
```

Define a handler (protobuf is optionally supported - see [example](https://github.com/go-micro/examples/blob/main/helloworld/main.go)) 

```golang
type Request struct {
        Name string `json:"name"`
}

type Response struct {
        Message string `json:"message"`
}

type Helloworld struct{}

func (h *Helloworld) Greeting(ctx context.Context, req *Request, rsp *Response) error {
        rsp.Message = "Hello " + req.Name
        return nil
}
```

Create, initialise and run the service

```golang
// create a new service
service := micro.NewService(
    micro.Name("helloworld"),
    micro.Handle(new(Helloworld)),
)

// initialise flags
service.Init()

// start the service
service.Run()
```

Optionally set fixed address

```golang
service := micro.NewService(
    // set address
    micro.Address(":8080"),
)
```

Call it via curl

```
curl -XPOST \
     -H 'Content-Type: application/json' \
     -H 'Micro-Endpoint: Helloworld.Greeting' \
     -d '{"name": "alice"}' \
      http://localhost:8080
```