micro/README.md

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# Go Micro [![GoDoc](https://godoc.org/github.com/micro/go-micro?status.svg)](https://godoc.org/github.com/micro/go-micro) [![Travis CI](https://travis-ci.org/micro/go-micro.svg?branch=master)](https://travis-ci.org/micro/go-micro)
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Go Micro is a pluggable RPC based microservice library which provides the fundamental building blocks for writing distributed applications. It is part of the [Micro](https://github.com/micro/micro) toolchain. It supports Proto-RPC and JSON-RPC as the request/response protocol out of the box and defaults to Consul for discovery.
Every aspect of go-micro is pluggable.
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An example server can be found in examples/server.
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- [Mailing List](https://groups.google.com/forum/#!forum/micro-services)
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- [Slack](https://micro-services.slack.com) : [auto-invite](http://micro-invites.herokuapp.com/)
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## Features
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Feature | Package | Built-in Plugin | Description
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------- | ------- | --------- | -----------
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Discovery | [Registry](https://godoc.org/github.com/micro/go-micro/registry) | consul | A way of locating services to communicate with
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Client | [Client](https://godoc.org/github.com/micro/go-micro/client) | rpc | Used to make RPC requests to a service
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Codec | [Codec](https://godoc.org/github.com/micro/go-micro/codec) | proto,json | Encoding/Decoding handler for requests
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Balancer | [Selector](https://godoc.org/github.com/micro/go-micro/selector) | random | Service node filter and pool
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Server | [Server](https://godoc.org/github.com/micro/go-micro/server) | rpc | Listens and serves RPC requests
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Pub/Sub | [Broker](https://godoc.org/github.com/micro/go-micro/broker) | http | Publish and Subscribe to events
Transport | [Transport](https://godoc.org/github.com/micro/go-micro/transport) | http | Communication mechanism between services
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## Go Plugins
By default go-micro only provides a single implementation of each interface. Plugins can be found at [github.com/micro/go-plugins](https://github.com/micro/go-plugins). Contributions welcome!
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## Prerequisites
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Consul is the default discovery mechanism provided in go-micro. Discovery is however pluggable so you can used etcd, kubernetes, zookeeper, etc.
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### Install Consul
[https://www.consul.io/intro/getting-started/install.html](https://www.consul.io/intro/getting-started/install.html)
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## Getting Started
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### Run Consul
```
$ consul agent -server -bootstrap-expect 1 -data-dir /tmp/consul
```
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### Run Service
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```
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$ go run examples/service/main.go --logtostderr
I0102 00:22:26.413467 12018 rpc_server.go:297] Listening on [::]:62492
I0102 00:22:26.413803 12018 http_broker.go:115] Broker Listening on [::]:62493
I0102 00:22:26.414009 12018 rpc_server.go:212] Registering node: greeter-e6b2fc6f-b0e6-11e5-a42f-68a86d0d36b6
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```
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### Test Service
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```
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$ go run examples/service/main.go --client
Hello John
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```
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## Writing a service
### Create request/response proto
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`go-micro/examples/service/proto/greeter.proto`:
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```
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syntax = "proto3";
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service Greeter {
rpc Hello(HelloRequest) returns (HelloResponse) {}
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}
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message HelloRequest {
string name = 1;
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}
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message HelloResponse {
string greeting = 2;
}
```
### Install protobuf for code generation
We use a protobuf plugin for code generation. This is completely optional. Look at [examples/server](https://github.com/micro/go-micro/blob/master/examples/server/main.go)
and [examples/client](https://github.com/micro/go-micro/blob/master/examples/client/main.go) for examples without code generation.
```shell
go get github.com/micro/protobuf
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```
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Compile proto `protoc -I$GOPATH/src --go_out=plugins=micro:$GOPATH/src $GOPATH/src/github.com/micro/go-micro/examples/service/proto/greeter.proto`
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### Define the service
`go-micro/examples/service/main.go`:
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```go
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package main
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import (
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"fmt"
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micro "github.com/micro/go-micro"
proto "github.com/micro/go-micro/examples/service/proto"
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"golang.org/x/net/context"
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)
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type Greeter struct{}
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func (g *Greeter) Hello(ctx context.Context, req *proto.HelloRequest, rsp *proto.HelloResponse) error {
rsp.Greeting = "Hello " + req.Name
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return nil
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}
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func main() {
// Create a new service. Optionally include some options here.
service := micro.NewService(
micro.Name("greeter"),
micro.Version("latest"),
micro.Metadata(map[string]string{
"type": "helloworld",
}),
)
// Init will parse the command line flags. Any flags set will
// override the above settings. Options defined here will
// override anything set on the command line.
service.Init()
// Register handler
proto.RegisterGreeterHandler(service.Server(), new(Greeter))
// Run the server
if err := service.Run(); err != nil {
fmt.Println(err)
}
}
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```
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### Run service
```
go run examples/service/main.go --logtostderr
I0102 00:22:26.413467 12018 rpc_server.go:297] Listening on [::]:62492
I0102 00:22:26.413803 12018 http_broker.go:115] Broker Listening on [::]:62493
I0102 00:22:26.414009 12018 rpc_server.go:212] Registering node: greeter-e6b2fc6f-b0e6-11e5-a42f-68a86d0d36b6
```
### Define a client
`client.go`
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```go
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package main
import (
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"fmt"
micro "github.com/micro/go-micro"
proto "github.com/micro/go-micro/examples/service/proto"
"golang.org/x/net/context"
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)
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func main() {
// Create a new service. Optionally include some options here.
service := micro.NewService(micro.Name("greeter.client"))
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// Create new greeter client
greeter := proto.NewGreeterClient("greeter", service.Client())
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// Call the greeter
rsp, err := greeter.Hello(context.TODO(), &proto.HelloRequest{Name: "John"})
if err != nil {
fmt.Println(err)
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}
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// Print response
fmt.Println(rsp.Greeting)
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}
```
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### Run the client
```shell
go run client.go
Hello John
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```