456 lines
12 KiB
Markdown
456 lines
12 KiB
Markdown
# Go Micro [![License](https://img.shields.io/:license-apache-blue.svg)](https://opensource.org/licenses/Apache-2.0) [![GoDoc](https://godoc.org/github.com/micro/go-micro?status.svg)](https://godoc.org/github.com/micro/go-micro) [![Travis CI](https://api.travis-ci.org/micro/go-micro.svg?branch=master)](https://travis-ci.org/micro/go-micro) [![Go Report Card](https://goreportcard.com/badge/micro/go-micro)](https://goreportcard.com/report/github.com/micro/go-micro)
|
|
|
|
Go Micro is a pluggable RPC framework for distributed systems development.
|
|
|
|
The **micro** philosophy is sane defaults with a pluggable architecture. We provide defaults to get you started quickly but everything can be easily swapped out. It comes with built in support for {json,proto}-rpc encoding, consul or multicast dns for service discovery, http for communication and random hashed client side load balancing.
|
|
|
|
Plugins are available at [github.com/micro/go-plugins](https://github.com/micro/go-plugins).
|
|
|
|
Follow us on [Twitter](https://twitter.com/microhq) or join the [Slack](http://slack.micro.mu/) community.
|
|
|
|
## Features
|
|
|
|
Go Micro abstracts away the details of distributed systems. Here are the main features.
|
|
|
|
- **Service Discovery** - Automatic service registration and name resolution
|
|
- **Load Balancing** - Client side load balancing built on discovery
|
|
- **Sync Comms** - RPC based communication with support for bidirectional streaming
|
|
- **Async Comms** - Native PubSub messaging built in for event driven architectures
|
|
- **Message Encoding** - Dynamic encoding based on content-type with protobuf and json out of the box
|
|
|
|
Go Micro supports both the Service and Function programming models. Read on to learn more.
|
|
|
|
## Docs
|
|
|
|
For more detailed information on the architecture, installation and use of go-micro checkout the [docs](https://micro.mu/docs).
|
|
|
|
## Learn By Example
|
|
|
|
An example service can be found in [**examples/service**](https://github.com/micro/examples/tree/master/service) and function in [**examples/function**](https://github.com/micro/examples/tree/master/function).
|
|
|
|
The [**examples**](https://github.com/micro/examples) directory contains examples for using things such as middleware/wrappers, selector filters, pub/sub, grpc, plugins and much more. For the complete greeter example look at [**examples/greeter**](https://github.com/micro/examples/tree/master/greeter). Other examples can be found throughout the GitHub repository.
|
|
|
|
Watch the [Golang UK Conf 2016](https://www.youtube.com/watch?v=xspaDovwk34) video for a high level overview.
|
|
|
|
## Getting started
|
|
|
|
- [Install Protobuf](#install-protobuf)
|
|
- [Service Discovery](#service-discovery)
|
|
- [Writing a Service](#writing-a-service)
|
|
- [Writing a Function](#writing-a-function)
|
|
- [Publish & Subscribe](#publish--subscribe)
|
|
- [Plugins](#plugins)
|
|
- [Wrappers](#wrappers)
|
|
|
|
## Install Protobuf
|
|
|
|
Protobuf is required for code generation
|
|
|
|
You'll need to install:
|
|
|
|
- [protoc-gen-micro](https://github.com/micro/protoc-gen-micro)
|
|
|
|
## Service Discovery
|
|
|
|
Service discovery is used to resolve service names to addresses.
|
|
|
|
### Consul
|
|
|
|
[Consul](https://www.consul.io/) is used as the default service discovery system.
|
|
|
|
Discovery is pluggable. Find plugins for etcd, kubernetes, zookeeper and more in the [micro/go-plugins](https://github.com/micro/go-plugins) repo.
|
|
|
|
[Install guide](https://www.consul.io/intro/getting-started/install.html)
|
|
|
|
### Multicast DNS
|
|
|
|
[Multicast DNS](https://en.wikipedia.org/wiki/Multicast_DNS) is a built in service discovery plugin for a zero dependency configuration.
|
|
|
|
Pass `--registry=mdns` to any command or the enviroment variable `MICRO_REGISTRY=mdns`
|
|
|
|
```
|
|
MICRO_REGISTRY=mdns go run main.go
|
|
```
|
|
|
|
## Writing a service
|
|
|
|
This is a simple greeter RPC service example
|
|
|
|
Find this example at [examples/service](https://github.com/micro/examples/tree/master/service).
|
|
|
|
### Create service proto
|
|
|
|
One of the key requirements of microservices is strongly defined interfaces. Micro uses protobuf to achieve this.
|
|
|
|
Here we define the Greeter handler with the method Hello. It takes a HelloRequest and HelloResponse both with one string arguments.
|
|
|
|
```proto
|
|
syntax = "proto3";
|
|
|
|
service Greeter {
|
|
rpc Hello(HelloRequest) returns (HelloResponse) {}
|
|
}
|
|
|
|
message HelloRequest {
|
|
string name = 1;
|
|
}
|
|
|
|
message HelloResponse {
|
|
string greeting = 2;
|
|
}
|
|
```
|
|
|
|
### Generate the proto
|
|
|
|
After writing the proto definition we must compile it using protoc with the micro plugin.
|
|
|
|
```shell
|
|
protoc --proto_path=$GOPATH/src:. --micro_out=. --go_out=. path/to/greeter.proto
|
|
```
|
|
|
|
### Write the service
|
|
|
|
Below is the code for the greeter service.
|
|
|
|
It does the following:
|
|
|
|
1. Implements the interface defined for the Greeter handler
|
|
2. Initialises a micro.Service
|
|
3. Registers the Greeter handler
|
|
4. Runs the service
|
|
|
|
```go
|
|
package main
|
|
|
|
import (
|
|
"context"
|
|
"fmt"
|
|
|
|
micro "github.com/micro/go-micro"
|
|
proto "github.com/micro/examples/service/proto"
|
|
)
|
|
|
|
type Greeter struct{}
|
|
|
|
func (g *Greeter) Hello(ctx context.Context, req *proto.HelloRequest, rsp *proto.HelloResponse) error {
|
|
rsp.Greeting = "Hello " + req.Name
|
|
return nil
|
|
}
|
|
|
|
func main() {
|
|
// Create a new service. Optionally include some options here.
|
|
service := micro.NewService(
|
|
micro.Name("greeter"),
|
|
)
|
|
|
|
// Init will parse the command line flags.
|
|
service.Init()
|
|
|
|
// Register handler
|
|
proto.RegisterGreeterHandler(service.Server(), new(Greeter))
|
|
|
|
// Run the server
|
|
if err := service.Run(); err != nil {
|
|
fmt.Println(err)
|
|
}
|
|
}
|
|
```
|
|
|
|
### Run service
|
|
```
|
|
go run examples/service/main.go
|
|
```
|
|
|
|
Output
|
|
```
|
|
2016/03/14 10:59:14 Listening on [::]:50137
|
|
2016/03/14 10:59:14 Broker Listening on [::]:50138
|
|
2016/03/14 10:59:14 Registering node: greeter-ca62b017-e9d3-11e5-9bbb-68a86d0d36b6
|
|
```
|
|
|
|
### Define a client
|
|
|
|
Below is the client code to query the greeter service.
|
|
|
|
The generated proto includes a greeter client to reduce boilerplate code.
|
|
|
|
```go
|
|
package main
|
|
|
|
import (
|
|
"context"
|
|
"fmt"
|
|
|
|
micro "github.com/micro/go-micro"
|
|
proto "github.com/micro/examples/service/proto"
|
|
)
|
|
|
|
|
|
func main() {
|
|
// Create a new service. Optionally include some options here.
|
|
service := micro.NewService(micro.Name("greeter.client"))
|
|
service.Init()
|
|
|
|
// Create new greeter client
|
|
greeter := proto.NewGreeterClient("greeter", service.Client())
|
|
|
|
// Call the greeter
|
|
rsp, err := greeter.Hello(context.TODO(), &proto.HelloRequest{Name: "John"})
|
|
if err != nil {
|
|
fmt.Println(err)
|
|
}
|
|
|
|
// Print response
|
|
fmt.Println(rsp.Greeting)
|
|
}
|
|
```
|
|
|
|
### Run the client
|
|
|
|
```shell
|
|
go run client.go
|
|
```
|
|
|
|
Output
|
|
```
|
|
Hello John
|
|
```
|
|
|
|
## Writing a Function
|
|
|
|
Go Micro includes the Function programming model.
|
|
|
|
A Function is a one time executing Service which exits after completing a request.
|
|
|
|
### Defining a Function
|
|
|
|
```go
|
|
package main
|
|
|
|
import (
|
|
"context"
|
|
|
|
proto "github.com/micro/examples/function/proto"
|
|
"github.com/micro/go-micro"
|
|
)
|
|
|
|
type Greeter struct{}
|
|
|
|
func (g *Greeter) Hello(ctx context.Context, req *proto.HelloRequest, rsp *proto.HelloResponse) error {
|
|
rsp.Greeting = "Hello " + req.Name
|
|
return nil
|
|
}
|
|
|
|
func main() {
|
|
// create a new function
|
|
fnc := micro.NewFunction(
|
|
micro.Name("greeter"),
|
|
)
|
|
|
|
// init the command line
|
|
fnc.Init()
|
|
|
|
// register a handler
|
|
fnc.Handle(new(Greeter))
|
|
|
|
// run the function
|
|
fnc.Run()
|
|
}
|
|
```
|
|
|
|
It's that simple.
|
|
|
|
## Publish & Subscribe
|
|
|
|
Go-micro has a built in message broker interface for event driven architectures.
|
|
|
|
PubSub operates on the same protobuf generated messages as RPC. They are encoded/decoded automatically and sent via the broker.
|
|
By default go-micro includes a point-to-point http broker but this can be swapped out via go-plugins.
|
|
|
|
### Publish
|
|
|
|
|
|
Create a new publisher with a `topic` name and service client
|
|
|
|
```
|
|
p := micro.NewPublisher("events", service.Client())
|
|
```
|
|
|
|
Publish a proto message
|
|
|
|
```
|
|
p.Publish(context.TODO(), &proto.Event{Name: "event"})
|
|
```
|
|
|
|
### Subscribe
|
|
|
|
Create a message handler. It's signature should be `func(context.Context, v interface{}) error`.
|
|
|
|
```
|
|
func ProcessEvent(ctx context.Context, event *proto.Event) error {
|
|
fmt.Printf("Got event %+v\n", event)
|
|
return nil
|
|
}
|
|
```
|
|
|
|
Register the message handler with a `topic`
|
|
|
|
```
|
|
micro.RegisterSubscriber("events", ProcessEvent)
|
|
```
|
|
|
|
## Plugins
|
|
|
|
By default go-micro only provides a few implementation of each interface at the core but it's completely pluggable. There's already dozens of plugins which are available at [github.com/micro/go-plugins](https://github.com/micro/go-plugins). Contributions are welcome!
|
|
|
|
### Build with plugins
|
|
|
|
If you want to integrate plugins simply link them in a separate file and rebuild
|
|
|
|
Create a plugins.go file
|
|
|
|
```go
|
|
import (
|
|
// etcd v3 registry
|
|
_ "github.com/micro/go-plugins/registry/etcdv3"
|
|
// nats transport
|
|
_ "github.com/micro/go-plugins/transport/nats"
|
|
// kafka broker
|
|
_ "github.com/micro/go-plugins/broker/kafka"
|
|
)
|
|
```
|
|
|
|
Build binary
|
|
|
|
```shell
|
|
// For local use
|
|
go build -i -o service ./main.go ./plugins.go
|
|
```
|
|
|
|
Flag usage of plugins
|
|
```shell
|
|
service --registry=etcdv3 --transport=nats --broker=kafka
|
|
```
|
|
|
|
### Plugin as option
|
|
|
|
Alternatively you can set the plugin as an option to a service
|
|
|
|
```go
|
|
|
|
import (
|
|
"github.com/micro/go-micro"
|
|
// etcd v3 registry
|
|
"github.com/micro/go-plugins/registry/etcdv3"
|
|
// nats transport
|
|
"github.com/micro/go-plugins/transport/nats"
|
|
// kafka broker
|
|
"github.com/micro/go-plugins/broker/kafka"
|
|
)
|
|
|
|
func main() {
|
|
registry := etcdv3.NewRegistry()
|
|
broker := kafka.NewBroker()
|
|
transport := nats.NewTransport()
|
|
|
|
service := micro.NewService(
|
|
micro.Name("greeter"),
|
|
micro.Registry(registry),
|
|
micro.Broker(broker),
|
|
micro.Transport(transport),
|
|
)
|
|
|
|
service.Init()
|
|
service.Run()
|
|
}
|
|
```
|
|
|
|
### Write plugins
|
|
|
|
Plugins are a concept built on Go's interface. Each package maintains a high level interface abstraction.
|
|
Simply implement the interface and pass it in as an option to the service.
|
|
|
|
The service discovery interface is called [Registry](https://godoc.org/github.com/micro/go-micro/registry#Registry).
|
|
Anything which implements this interface can be used as a registry. The same applies to the other packages.
|
|
|
|
```go
|
|
type Registry interface {
|
|
Register(*Service, ...RegisterOption) error
|
|
Deregister(*Service) error
|
|
GetService(string) ([]*Service, error)
|
|
ListServices() ([]*Service, error)
|
|
Watch() (Watcher, error)
|
|
String() string
|
|
}
|
|
```
|
|
|
|
Browse [go-plugins](https://github.com/micro/go-plugins) to get a better idea of implementation details.
|
|
|
|
## Wrappers
|
|
|
|
Go-micro includes the notion of middleware as wrappers. The client or handlers can be wrapped using the decorator pattern.
|
|
|
|
### Handler
|
|
|
|
Here's an example service handler wrapper which logs the incoming request
|
|
|
|
```go
|
|
// implements the server.HandlerWrapper
|
|
func logWrapper(fn server.HandlerFunc) server.HandlerFunc {
|
|
return func(ctx context.Context, req server.Request, rsp interface{}) error {
|
|
fmt.Printf("[%v] server request: %s", time.Now(), req.Method())
|
|
return fn(ctx, req, rsp)
|
|
}
|
|
}
|
|
```
|
|
|
|
It can be initialised when creating the service
|
|
|
|
```go
|
|
service := micro.NewService(
|
|
micro.Name("greeter"),
|
|
// wrap the handler
|
|
micro.WrapHandler(logWrapper),
|
|
)
|
|
```
|
|
|
|
### Client
|
|
|
|
Here's an example of a client wrapper which logs requests made
|
|
|
|
```go
|
|
type logWrapper struct {
|
|
client.Client
|
|
}
|
|
|
|
func (l *logWrapper) Call(ctx context.Context, req client.Request, rsp interface{}, opts ...client.CallOption) error {
|
|
fmt.Printf("[wrapper] client request to service: %s method: %s\n", req.Service(), req.Method())
|
|
return l.Client.Call(ctx, req, rsp)
|
|
}
|
|
|
|
// implements client.Wrapper as logWrapper
|
|
func logWrap(c client.Client) client.Client {
|
|
return &logWrapper{c}
|
|
}
|
|
```
|
|
|
|
It can be initialised when creating the service
|
|
|
|
```go
|
|
service := micro.NewService(
|
|
micro.Name("greeter"),
|
|
// wrap the client
|
|
micro.WrapClient(logWrap),
|
|
)
|
|
```
|
|
|
|
## Other Languages
|
|
|
|
Check out [ja-micro](https://github.com/Sixt/ja-micro) to write services in Java
|
|
|
|
## Sponsors
|
|
|
|
Open source development of Micro is sponsored by Sixt
|
|
|
|
<a href="https://micro.mu/blog/2016/04/25/announcing-sixt-sponsorship.html"><img src="https://micro.mu/sixt_logo.png" width=150px height="auto" /></a>
|