From b6c6b1327711c5acfa9ae2cf37fba59a8940ebe3 Mon Sep 17 00:00:00 2001
From: Asim Aslam <asim@aslam.me>
Date: Mon, 9 Sep 2019 19:09:28 -0700
Subject: [PATCH] Support plugin loading

---
 plugin/default.go  | 122 +++++++++++++++++++++++++++++++++++++++++++++
 plugin/plugin.go   |  29 +++++++++++
 plugin/template.go |  20 ++++++++
 3 files changed, 171 insertions(+)
 create mode 100644 plugin/default.go
 create mode 100644 plugin/plugin.go
 create mode 100644 plugin/template.go

diff --git a/plugin/default.go b/plugin/default.go
new file mode 100644
index 00000000..d9d01ec0
--- /dev/null
+++ b/plugin/default.go
@@ -0,0 +1,122 @@
+// Package plugin provides the ability to load plugins
+package plugin
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	pg "plugin"
+	"strings"
+	"text/template"
+
+	"github.com/micro/go-micro/broker"
+	"github.com/micro/go-micro/client"
+	"github.com/micro/go-micro/client/selector"
+	"github.com/micro/go-micro/config/cmd"
+	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/server"
+	"github.com/micro/go-micro/transport"
+)
+
+type plugin struct{}
+
+// Init sets up the plugin
+func (p *plugin) Init(c *Config) error {
+	switch c.Type {
+	case "broker":
+		pg, ok := c.NewFunc.(func(...broker.Option) broker.Broker)
+		if !ok {
+			return fmt.Errorf("Invalid plugin %s", c.Name)
+		}
+		cmd.DefaultBrokers[c.Name] = pg
+	case "client":
+		pg, ok := c.NewFunc.(func(...client.Option) client.Client)
+		if !ok {
+			return fmt.Errorf("Invalid plugin %s", c.Name)
+		}
+		cmd.DefaultClients[c.Name] = pg
+	case "registry":
+		pg, ok := c.NewFunc.(func(...registry.Option) registry.Registry)
+		if !ok {
+			return fmt.Errorf("Invalid plugin %s", c.Name)
+		}
+		cmd.DefaultRegistries[c.Name] = pg
+
+	case "selector":
+		pg, ok := c.NewFunc.(func(...selector.Option) selector.Selector)
+		if !ok {
+			return fmt.Errorf("Invalid plugin %s", c.Name)
+		}
+		cmd.DefaultSelectors[c.Name] = pg
+	case "server":
+		pg, ok := c.NewFunc.(func(...server.Option) server.Server)
+		if !ok {
+			return fmt.Errorf("Invalid plugin %s", c.Name)
+		}
+		cmd.DefaultServers[c.Name] = pg
+	case "transport":
+		pg, ok := c.NewFunc.(func(...transport.Option) transport.Transport)
+		if !ok {
+			return fmt.Errorf("Invalid plugin %s", c.Name)
+		}
+		cmd.DefaultTransports[c.Name] = pg
+	}
+	return fmt.Errorf("Unknown plugin type: %s for %s", c.Type, c.Name)
+}
+
+// Load loads a plugin created with `go build -buildmode=plugin`
+func (p *plugin) Load(path string) (*Config, error) {
+	plugin, err := pg.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	s, err := plugin.Lookup("Plugin")
+	if err != nil {
+		return nil, err
+	}
+	pl, ok := s.(*Config)
+	if !ok {
+		return nil, errors.New("could not cast Plugin object")
+	}
+	return pl, nil
+}
+
+// Generate creates a go file at the specified path.
+// You must use `go build -buildmode=plugin`to build it.
+func (p *plugin) Generate(path string, c *Config) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	t, err := template.New(c.Name).Parse(tmpl)
+	if err != nil {
+		return err
+	}
+	return t.Execute(f, c)
+}
+
+// Build generates a dso plugin using the go command `go build -buildmode=plugin`
+func (p *plugin) Build(path string, c *Config) error {
+	path = strings.TrimSuffix(path, ".so")
+
+	// create go file in tmp path
+	temp := os.TempDir()
+	base := filepath.Base(path)
+	goFile := filepath.Join(temp, base+".go")
+
+	// generate .go file
+	if err := p.Generate(goFile, c); err != nil {
+		return err
+	}
+	// remove .go file
+	defer os.Remove(goFile)
+
+	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil && !os.IsExist(err) {
+		return fmt.Errorf("Failed to create dir %s: %v", filepath.Dir(path), err)
+	}
+	cmd := exec.Command("go", "build", "-buildmode=plugin", "-o", path+".so", goFile)
+	return cmd.Run()
+}
diff --git a/plugin/plugin.go b/plugin/plugin.go
new file mode 100644
index 00000000..68291a36
--- /dev/null
+++ b/plugin/plugin.go
@@ -0,0 +1,29 @@
+// Package plugin provides the ability to load plugins
+package plugin
+
+// Plugin is a plugin loaded from a file
+type Plugin interface {
+	// Initialise a plugin with the config
+	Init(c *Config) error
+	// Load loads a .so plugin at the given path
+	Load(path string) (*Config, error)
+	// Build a .so plugin with config at the path specified
+	Build(path string, c *Config) error
+}
+
+// Config is the plugin config
+type Config struct {
+	// Name of the plugin e.g rabbitmq
+	Name string
+	// Type of the plugin e.g broker
+	Type string
+	// Path specifies the import path
+	Path string
+	// NewFunc creates an instance of the plugin
+	NewFunc interface{}
+}
+
+// NewPlugin creates a new plugin interface
+func NewPlugin() Plugin {
+	return &plugin{}
+}
diff --git a/plugin/template.go b/plugin/template.go
new file mode 100644
index 00000000..dd559bfa
--- /dev/null
+++ b/plugin/template.go
@@ -0,0 +1,20 @@
+package plugin
+
+var (
+	tmpl = `
+package main
+
+import (
+	"github.com/micro/go-micro/plugin"
+
+	"{{.Path}}"
+)
+
+var Plugin = plugin.Config{
+	Name: "{{.Name}}",
+	Type: "{{.Type}}",
+	Path: "{{.Path}}",
+	NewFunc: {{.Name}}.{{.NewFunc}},
+}
+`
+)