osdconfig lib update

code refactoring and simplification.

Signed-off-by: Saurabh Deoras <[email protected]>

osdconfig/README.md

@@ -0,0 +1,59 @@
+# osdconfig
+osdconfig is a library to work with distributed configuration parameters. It defines an interface and provides an
+implementation against KVDB backend.
+
+General purpose of this package is as follows:
+* Allow users to register their callback functions on updates to backend
+* Allow users to set/get config parameters
+
+# installation
+osdconfig is written in go (golang). It can be installed using go get
+```bash
+$ go get github.com/libopenstorage/openstorage/osdconfig/...
+```
+
+# example
+Create an instance of kvdb
+```go
+kv, err := kvdb.New(mem.Name, "", []string{}, nil, nil)
+if err != nil {
+    logrus.Fatal(err)
+}
+```
+
+Create an instance of osdconfig manager
+```go
+manager, err := osdconfig.NewManager(kv)
+if err != nil {
+	// do something
+}
+defer manager.Close()
+```
+
+Define a function literal that can be registered to watch for changes
+```go
+f := func(config *osdconfig.Config) error {
+	// do something with config (say print)
+	fmt.Println(config)
+	return nil
+}
+```
+
+Register this function literal to watch on kvdb changes
+```go
+if err := manager.WatchCluster("watcher", f); err != nil {
+	// do something
+}
+```
+
+Update cluster config on kvdb
+```go
+conf := new(osdconfig.ClusterConfig)
+conf.ClusterID = "myID"
+if err := manager.SetClusterConf(conf); err != nil {
+	// do something
+	return
+}
+```
+
+once updates are pushed to backend (kvdb in this implementation), callback function is called