Add proxy mode.

error/error.go

@@ -51,6 +51,10 @@ const (
 
 	EcodeWatcherCleared    = 400
 	EcodeEventIndexCleared = 401
+	EcodeProxyInternal = 402
+	EcodeInvalidActiveSize = 403
+	EcodeInvalidPromoteDelay = 404
+	EcodePromoteError = 405
 )
 
 func init() {
@@ -86,6 +90,9 @@ func init() {
 	// etcd related errors
 	errors[EcodeWatcherCleared] = "watcher is cleared due to etcd recovery"
 	errors[EcodeEventIndexCleared] = "The event in requested index is outdated and cleared"
+	errors[EcodeProxyInternal] = "Proxy Internal Error"
+	errors[EcodeInvalidActiveSize] = "Invalid active size"
+	errors[EcodeInvalidPromoteDelay] = "Proxy promote delay"
 
 }