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Go Micro 
Go Micro is a pluggable RPC framework for microservices. It is part of the 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.
Follow us on Twitter or join the Slack community.
Features
Go Micro abstracts away the details of distributed systems. Here are the main features.
- Service Discovery - Automatic registration and name resolution with service discovery
- Load Balancing - Smart client side load balancing of services built on discovery
- Synchronous Comms - RPC based communication with support for bidirectional streaming
- Asynchronous Comms - PubSub interface built in for event driven architectures
- Message Encoding - Dynamic encoding based on content-type with protobuf and json out of the box
- Service Interface - All features are packaged in a simple high level interface for developing microservices
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.
Learn By Example
An example service can be found in examples/service and function in examples/function.
The 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. Other examples can be found throughout the GitHub repository.
Watch the Golang UK Conf 2016 video for a high level overview.
Getting Started
This is a quick getting started guide with the greeter service example.
Prereq: Service Discovery
Service discovery is required to resolve services to their addresses.
The default discovery plugin is consul. Discovery is however pluggable so you can use etcd, kubernetes, zookeeper, etc. Plugins are in micro/go-plugins.
Multicast DNS
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
go run main.go --registry=mdns
Consul
Here's a quick start for the default service discovery system consul.
On Mac OS
brew install consul
consul agent -dev
Further installation instructions
Run Service
go get github.com/micro/examples/service && service
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
Call Service
service --run_client
Output
Hello John
Writing a service
This is a simple greeter RPC service example
Find this example at examples/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.
syntax = "proto3";
service Greeter {
rpc Hello(HelloRequest) returns (HelloResponse) {}
}
message HelloRequest {
string name = 1;
}
message HelloResponse {
string greeting = 2;
}
Install protobuf
Install protobuf
Now install the micro fork of protoc-gen-go. The protobuf compiler for Go.
go get github.com/micro/protobuf/{proto,protoc-gen-go}
Generate the proto
After writing the proto definition we must compile it using protoc with the micro plugin.
protoc -I$GOPATH/src --go_out=plugins=micro:$GOPATH/src \
$GOPATH/src/github.com/micro/examples/service/proto/greeter.proto
Write the service
Below is the code for the greeter service.
It does the following:
- Implements the interface defined for the Greeter handler
- Initialises a micro.Service
- Registers the Greeter handler
- Runs the service
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"),
)
// 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.
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
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
package main
import (
proto "github.com/micro/examples/function/proto"
"github.com/micro/go-micro"
"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 function
fnc := micro.NewFunction(
micro.Name("go.micro.fnc.greeter"),
)
// init the command line
fnc.Init()
// register a handler
fnc.Handle(new(Greeter))
// run the function
fnc.Run()
}
It's that simple.
How it works
Go Micro is a framework that addresses the fundamental requirements for writing 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. 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
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
// For local use
go build -i -o service ./main.go ./plugins.go
Flag usage of plugins
service --registry=etcdv3 --transport=nats --broker=kafka
Other Languages
Check out ja-micro to write services in Java
Sponsors
Open source development of Micro is sponsored by Sixt
