initial support for plugins

backends/config.go

@@ -14,6 +14,7 @@ import (
 	"github.com/HeavyHorst/remco/backends/etcd"
 	"github.com/HeavyHorst/remco/backends/file"
 	"github.com/HeavyHorst/remco/backends/mock"
+	"github.com/HeavyHorst/remco/backends/plugin"
 	"github.com/HeavyHorst/remco/backends/redis"
 	"github.com/HeavyHorst/remco/backends/vault"
 	"github.com/HeavyHorst/remco/backends/zookeeper"
@@ -29,6 +30,7 @@ type Config struct {
 	Redis     *redis.Config
 	Zookeeper *zookeeper.Config
 	Mock      *mock.Config
+	Plugin    []plugin.Plugin
 }
 
 func (c *Config) GetBackends() []template.BackendConfig {

backends/plugin/plugin.go

@@ -0,0 +1,89 @@
+/*
+ * This file is part of remco.
+ * © 2016 The Remco Authors
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+package plugin
+
+import (
+	"context"
+	"net/rpc"
+	"net/rpc/jsonrpc"
+	"os"
+	"path"
+
+	"github.com/HeavyHorst/easyKV"
+	berr "github.com/HeavyHorst/remco/backends/error"
+	"github.com/HeavyHorst/remco/log"
+	"github.com/HeavyHorst/remco/template"
+	"github.com/Sirupsen/logrus"
+	"github.com/natefinch/pie"
+)
+
+type plug struct {
+	client *rpc.Client
+}
+
+// Plugin represents the config for a plugin.
+type Plugin struct {
+	// the path to the plugin executable
+	Path   string
+	Config map[string]interface{}
+	template.Backend
+}
+
+// Connect creates the connection to the plugin and sends the config map to the same.
+func (p *Plugin) Connect() (template.Backend, error) {
+	if p == nil {
+		return template.Backend{}, berr.ErrNilConfig
+	}
+
+	p.Backend.Name = path.Base(p.Path)
+
+	client, err := pie.StartProviderCodec(jsonrpc.NewClientCodec, os.Stderr, p.Path)
+	if err != nil {
+		return p.Backend, err
+	}
+
+	if p.Backend.Watch {
+		log.WithFields(logrus.Fields{
+			"backend": p.Backend.Name,
+		}).Warn("Watch is not supported, using interval instead")
+		p.Backend.Watch = false
+	}
+
+	plugin := &plug{client}
+	if err := plugin.Init(p.Config); err != nil {
+		return p.Backend, err
+	}
+
+	p.Backend.ReadWatcher = plugin
+	return p.Backend, nil
+}
+
+// Init sends the config map to the plugin
+// the plugin can then run some initialization tasks
+func (p *plug) Init(config map[string]interface{}) error {
+	var result bool
+	return p.client.Call("Plugin.Init", config, &result)
+}
+
+// GetValues queries the plugin for keys
+func (p *plug) GetValues(keys []string) (result map[string]string, err error) {
+	err = p.client.Call("Plugin.GetValues", keys, &result)
+	return result, err
+}
+
+// Close closes the client connection
+func (p *plug) Close() {
+	p.client.Call("Plugin.Close", nil, nil)
+	p.client.Close()
+}
+
+// WatchPrefix is not supported for now
+func (p *plug) WatchPrefix(prefix string, ctx context.Context, opts ...easyKV.WatchOption) (uint64, error) {
+	return 0, easyKV.ErrWatchNotSupported
+}

config/config.go

@@ -140,10 +140,15 @@ func (c *Configuration) configureLogger() {
 
 func (r *Resource) Init(ctx context.Context, reapLock *sync.RWMutex) (*template.Resource, error) {
 	var backendList []template.Backend
+	backendConfigs := r.Backend.GetBackends()
+
+	for _, v := range r.Backend.Plugin {
+		backendConfigs = append(backendConfigs, &v)
+	}
 
 	// try to connect to all backends
 	// connection to all backends must succeed to continue
-	for _, config := range r.Backend.GetBackends() {
+	for _, config := range backendConfigs {
 	retryloop:
 		for {
 			select {