plugins

Plugins

The micro toolkit supports plugins for the binary itself. These are separate from go-micro plugins.

Plugins can be used to add flags, commands and middleware handlers. An example would be authentication, logging, tracing, etc. Existing plugins can be found in go-plugins/micro.

A simple example

Here's a simple example of a plugin that adds a flag and then prints the value

The plugin

Create a plugin.go file in the top level dir

package main

import (
	"log"
	"github.com/micro/cli"
	"github.com/micro/micro/plugin"
)

func init() {
	plugin.Register(plugin.NewPlugin(
		plugin.WithName("example"),
		plugin.WithFlag(cli.StringFlag{
			Name:   "example_flag",
			Usage:  "This is an example plugin flag",
			EnvVar: "EXAMPLE_FLAG",
			Value: "avalue",
		}),
		plugin.WithInit(func(ctx *cli.Context) error {
			log.Println("Got value for example_flag", ctx.String("example_flag"))
			return nil
		}),
	))
}

Build with plugin

Simply build micro with the plugin

go build -o micro ./main.go ./plugin.go

Go-Micro Plugins

Plugins can be added to go-micro in the following ways. By doing so they'll be available to set via command line args or environment variables.

Import Plugins

import (
	"github.com/micro/go-micro/cmd"
	_ "github.com/micro/go-plugins/broker/rabbitmq"
	_ "github.com/micro/go-plugins/registry/kubernetes"
	_ "github.com/micro/go-plugins/transport/nats"
)

func main() {
	// Parse CLI flags
	cmd.Init()
}

The same is achieved when calling service.Init

import (
	"github.com/micro/go-micro"
	_ "github.com/micro/go-plugins/broker/rabbitmq"
	_ "github.com/micro/go-plugins/registry/kubernetes"
	_ "github.com/micro/go-plugins/transport/nats"
)

func main() {
	service := micro.NewService(
		// Set service name
		micro.Name("my.service"),
	)

	// Parse CLI flags
	service.Init()
}

Use via CLI Flags

Activate via a command line flag

go run service.go --broker=rabbitmq --registry=kubernetes --transport=nats

Use Plugins Directly

CLI Flags provide a simple way to initialise plugins but you can do the same yourself.

import (
	"github.com/micro/go-micro"
	"github.com/micro/go-plugins/registry/kubernetes"
)

func main() {
	registry := kubernetes.NewRegistry() //a default to using env vars for master API

	service := micro.NewService(
		// Set service name
		micro.Name("my.service"),
		// Set service registry
		micro.Registry(registry),
	)
}

Build Pattern

You may want to swap out plugins using automation or add plugins to the micro toolkit. An easy way to do this is by maintaining a separate file for plugin imports and including it during the build.

Create file plugins.go

package main

import (
	_ "github.com/micro/go-plugins/broker/rabbitmq"
	_ "github.com/micro/go-plugins/registry/kubernetes"
	_ "github.com/micro/go-plugins/transport/nats"
)

Build with plugins.go

go build -o service main.go plugins.go

Run with plugins

service --broker=rabbitmq --registry=kubernetes --transport=nats