From 01b11041750af9d9f50c8b069334c95bb9f9537f Mon Sep 17 00:00:00 2001
From: Armon Dadgar <armon.dadgar@gmail.com>
Date: Fri, 7 Feb 2014 11:58:24 -0800
Subject: [PATCH] agent: adding ability to pause syncing

---
 command/agent/local.go | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/command/agent/local.go b/command/agent/local.go
index f4d3b9a96f..f7a0d376df 100644
--- a/command/agent/local.go
+++ b/command/agent/local.go
@@ -6,6 +6,7 @@ import (
 	"log"
 	"reflect"
 	"sync"
+	"sync/atomic"
 	"time"
 )
 
@@ -24,6 +25,10 @@ type syncStatus struct {
 // and checks. We used it to perform anti-entropy with the
 // catalog representation
 type localState struct {
+	// paused is used to check if we are paused. Must be the first
+	// element due to a go bug.
+	paused int32
+
 	sync.Mutex
 	logger *log.Logger
 
@@ -66,6 +71,23 @@ func (l *localState) changeMade() {
 	}
 }
 
+// Pause is used to pause state syncronization, this can be
+// used to make batch changes
+func (l *localState) Pause() {
+	atomic.StoreInt32(&l.paused, 1)
+}
+
+// Unpause is used to resume state syncronization
+func (l *localState) Unpause() {
+	atomic.StoreInt32(&l.paused, 0)
+	l.changeMade()
+}
+
+// isPaused is used to check if we are paused
+func (l *localState) isPaused() bool {
+	return atomic.LoadInt32(&l.paused) == 1
+}
+
 // AddService is used to add a service entry to the local state.
 // This entry is persistent and the agent will make a best effort to
 // ensure it is registered
@@ -200,6 +222,10 @@ SYNC:
 		case <-aeTimer:
 			goto SYNC
 		case <-l.triggerCh:
+			// Skip the sync if we are paused
+			if l.isPaused() {
+				continue
+			}
 			if err := l.syncChanges(); err != nil {
 				l.logger.Printf("[ERR] agent: failed to sync changes: %v", err)
 			}