328 lines
12 KiB
Markdown
328 lines
12 KiB
Markdown
# Go Micro [](https://opensource.org/licenses/Apache-2.0) [](https://godoc.org/github.com/micro/go-micro) [](https://travis-ci.org/micro/go-micro) [](https://goreportcard.com/report/github.com/micro/go-micro)
|
|
|
|
Go Micro is a pluggable RPC framework for **microservices**. It is part of the [Micro](https://github.com/micro/micro) toolkit.
|
|
|
|
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.
|
|
|
|
Everything in go-micro is **pluggable**. You can find and contribute to plugins at [github.com/micro/go-plugins](https://github.com/micro/go-plugins).
|
|
|
|
Follow us on Twitter at [@MicroHQ](https://twitter.com/microhq), join the [Slack](https://micro-services.slack.com) community [here](http://slack.micro.mu/) or
|
|
check out the [Mailing List](https://groups.google.com/forum/#!forum/microhq).
|
|
|
|
## Features
|
|
|
|
Go Micro abstracts way the details of distributed systems. Here are the main features.
|
|
|
|
- **Service Discovery** - Applications are automatically registered with service discovery so they can find each other.
|
|
- **Load Balancing** - Smart client side load balancing is used to balance requests between instances of a service.
|
|
- **Synchronous Communication** - Request-response is provided as a bidirectional streaming transport layer.
|
|
- **Asynchronous Communication** - Microservices should promote an event driven architecture. Publish and Subscribe semantics are built in.
|
|
- **Message Encoding** - Micro services can encode requests in a number of encoding formats and seamlessly decode based on the Content-Type header.
|
|
- **RPC Client/Server** - The client and server leverage the above features and provide a clean simple interface for building microservices.
|
|
|
|
## 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). The [**examples**](https://github.com/micro/examples) directory contains many more examples for using things such as middleware/wrappers, selector filters, pub/sub and code generation.
|
|
|
|
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.
|
|
|
|
Check out the blog post to learn how to write go-micro services [https://micro.mu/blog/2016/03/28/go-micro.html](https://micro.mu/blog/2016/03/28/go-micro.html) or watch the talk from the [Golang UK Conf 2016](https://www.youtube.com/watch?v=xspaDovwk34).
|
|
|
|
## Getting Started
|
|
|
|
This is a quick getting started guide with the greeter service example.
|
|
|
|
### Prerequisites: Service Discovery
|
|
|
|
There's just one prerequisite. We need a service discovery system to resolve service names to their address.
|
|
The default discovery mechanism used in go-micro is Consul. Discovery is however pluggable so you can used
|
|
etcd, kubernetes, zookeeper, etc. Plugins can be found in [micro/go-plugins](https://github.com/micro/go-plugins).
|
|
|
|
### Multicast DNS
|
|
|
|
We can use multicast DNS with the built in MDNS registry for a zero dependency configuration.
|
|
|
|
Just pass `--registry=mdns` to any command
|
|
```
|
|
$ go run main.go --registry=mdns
|
|
```
|
|
|
|
### Consul
|
|
|
|
Alternatively we can use the default discovery system which is Consul.
|
|
|
|
**Mac OS**
|
|
```
|
|
brew install consul
|
|
consul agent -dev
|
|
```
|
|
|
|
**Docker**
|
|
```
|
|
docker run consul
|
|
```
|
|
|
|
[Further installation instructions](https://www.consul.io/intro/getting-started/install.html)
|
|
|
|
### Run Service
|
|
|
|
```
|
|
$ go get github.com/micro/examples/service && service
|
|
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
|
|
```
|
|
|
|
### Call Service
|
|
```
|
|
$ service --run_client
|
|
Hello John
|
|
```
|
|
|
|
## Writing a service
|
|
|
|
### Create service proto
|
|
|
|
One of the key requirements of microservices is strongly defined interfaces so we utilised protobuf to define the handler and request/response.
|
|
Here's a definition for the Greeter handler with the method Hello which takes a HelloRequest and HelloResponse both with one string arguments.
|
|
|
|
`go-micro/examples/service/proto/greeter.proto`:
|
|
|
|
```proto
|
|
syntax = "proto3";
|
|
|
|
service Greeter {
|
|
rpc Hello(HelloRequest) returns (HelloResponse) {}
|
|
}
|
|
|
|
message HelloRequest {
|
|
string name = 1;
|
|
}
|
|
|
|
message HelloResponse {
|
|
string greeting = 2;
|
|
}
|
|
```
|
|
|
|
### Install protobuf
|
|
|
|
We use a protobuf plugin for code generation. This is completely optional. Look at [examples/server](https://github.com/micro/examples/blob/master/server/main.go)
|
|
and [examples/client](https://github.com/micro/examples/blob/master/client/main.go) for examples without code generation.
|
|
|
|
```shell
|
|
go get github.com/micro/protobuf/{proto,protoc-gen-go}
|
|
```
|
|
|
|
There's still a need for proto compiler to generate Go stub code from our proto file. You can either use the micro fork above or the official repo `github.com/golang/protobuf`.
|
|
|
|
### Compile the proto
|
|
|
|
```shell
|
|
protoc -I$GOPATH/src --go_out=plugins=micro:$GOPATH/src \
|
|
$GOPATH/src/github.com/micro/examples/service/proto/greeter.proto
|
|
```
|
|
|
|
### Define the service
|
|
|
|
Below is the code sample for the Greeter service. It basically implements the interface defined above for the Greeter handler,
|
|
initialises the service, registers the handler and then runs itself. Simple as that.
|
|
|
|
`go-micro/examples/service/main.go`:
|
|
|
|
```go
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
|
|
micro "github.com/micro/go-micro"
|
|
proto "github.com/micro/examples/service/proto"
|
|
"golang.org/x/net/context"
|
|
)
|
|
|
|
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"),
|
|
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)
|
|
}
|
|
}
|
|
```
|
|
|
|
### Run service
|
|
```
|
|
go run examples/service/main.go
|
|
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. Notice we're using the code generated client interface `proto.NewGreeterClient`.
|
|
This reduces the amount of boiler plate code we need to write. The greeter client can be reused throughout the code if need be.
|
|
|
|
`client.go`
|
|
|
|
```go
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
|
|
micro "github.com/micro/go-micro"
|
|
proto "github.com/micro/examples/service/proto"
|
|
"golang.org/x/net/context"
|
|
)
|
|
|
|
|
|
func main() {
|
|
// Create a new service. Optionally include some options here.
|
|
service := micro.NewService(micro.Name("greeter.client"))
|
|
|
|
// 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
|
|
Hello John
|
|
```
|
|
|
|
## How does it work?
|
|
|
|
<p align="center">
|
|
<img src="go-micro.png" />
|
|
</p>
|
|
|
|
Go Micro is a framework that addresses the fundamental requirements to write microservices.
|
|
|
|
Let's dig into the core components.
|
|
|
|
### Registry
|
|
|
|
The registry provides a service discovery mechanism to resolve names to addresses. It can be backed by consul, etcd, zookeeper, dns, gossip, etc.
|
|
Services should register using the registry on startup and deregister on shutdown. Services can optionally provide an expiry TTL and reregister
|
|
on an interval to ensure liveness and that the service is cleaned up if it dies.
|
|
|
|
### Selector
|
|
|
|
The selector is a load balancing abstraction which builds on the registry. It allows services to be "filtered" using filter functions and "selected"
|
|
using a choice of algorithms such as random, roundrobin, leastconn, etc. The selector is leveraged by the Client when making requests. The client
|
|
will use the selector rather than the registry as it provides that built in mechanism of load balancing.
|
|
|
|
### Transport
|
|
|
|
The transport is the interface for synchronous request/response communication between services. It's akin to the golang net package but provides
|
|
a higher level abstraction which allows us to switch out communication mechanisms e.g http, rabbitmq, websockets, NATS. The transport also
|
|
supports bidirectional streaming. This is powerful for client side push to the server.
|
|
|
|
### Broker
|
|
|
|
The broker provides an interface to a message broker for asynchronous pub/sub communication. This is one of the fundamental requirements of an event
|
|
driven architecture and microservices. By default we use an inbox style point to point HTTP system to minimise the number of dependencies required
|
|
to get started. However there are many message broker implementations available in go-plugins e.g RabbitMQ, NATS, NSQ, Google Cloud Pub Sub.
|
|
|
|
### Codec
|
|
|
|
The codec is used for encoding and decoding messages before transporting them across the wire. This could be json, protobuf, bson, msgpack, etc.
|
|
Where this differs from most other codecs is that we actually support the RPC format here as well. So we have JSON-RPC, PROTO-RPC, BSON-RPC, etc.
|
|
It separates encoding from the client/server and provides a powerful method for integrating other systems such as gRPC, Vanadium, etc.
|
|
|
|
### Server
|
|
|
|
The server is the building block for writing a service. Here you can name your service, register request handlers, add middeware, etc. The service
|
|
builds on the above packages to provide a unified interface for serving requests. The built in server is an RPC system. In the future there maybe
|
|
other implementations. The server also allows you to define multiple codecs to serve different encoded messages.
|
|
|
|
### Client
|
|
|
|
The client provides an interface to make requests to services. Again like the server, it builds on the other packages to provide a unified interface
|
|
for finding services by name using the registry, load balancing using the selector, making synchronous requests with the transport and asynchronous
|
|
messaging using the broker.
|
|
|
|
|
|
The above components are combined at the top-level of micro as a **Service**.
|
|
|
|
## 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
|
|
```
|
|
|
|
## 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>
|