From f67217297c462d08c799a2da5b8c0ff908568ca1 Mon Sep 17 00:00:00 2001
From: Diptanu Choudhury <diptanuc@gmail.com>
Date: Tue, 29 Nov 2016 07:37:43 -0800
Subject: [PATCH] Ensuring allocs are not added multiple times to blocking
 queue

---
 client/client.go | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/client/client.go b/client/client.go
index 9a4e47d1b..329c21c20 100644
--- a/client/client.go
+++ b/client/client.go
@@ -1370,22 +1370,32 @@ func (c *Client) runAllocs(update *allocUpdates) {
 	for _, add := range diff.added {
 		// If the allocation is chained and the previous allocation hasn't
 		// terminated yet, then add the alloc to the blocked queue.
+		c.blockedAllocsLock.Lock()
 		ar, ok := c.getAllocRunners()[add.PreviousAllocation]
 		if ok && !ar.Alloc().Terminated() {
-			c.logger.Printf("[DEBUG] client: added alloc %q to blocked queue", add.ID)
-			c.blockedAllocsLock.Lock()
-			c.blockedAllocations[add.PreviousAllocation] = add
+			// Check if the alloc is already present in the blocked allocations
+			// map
+			if _, ok := c.blockedAllocations[add.PreviousAllocation]; !ok {
+				c.logger.Printf("[DEBUG] client: added alloc %q to blocked queue for previous allocation %q", add.ID,
+					add.PreviousAllocation)
+				c.blockedAllocations[add.PreviousAllocation] = add
+			}
 			c.blockedAllocsLock.Unlock()
 			continue
 		}
+		c.blockedAllocsLock.Unlock()
 
 		// This means the allocation has a previous allocation on another node
 		// so we will block for the previous allocation to complete
 		if add.PreviousAllocation != "" && !ok {
+			// Ensure that we are not blocking for the remote allocation if we
+			// have already blocked
 			c.migratingAllocsLock.Lock()
-			c.migratingAllocs[add.ID] = make(chan struct{})
+			if _, ok := c.migratingAllocs[add.ID]; !ok {
+				c.migratingAllocs[add.ID] = make(chan struct{})
+				go c.blockForRemoteAlloc(add)
+			}
 			c.migratingAllocsLock.Unlock()
-			go c.blockForRemoteAlloc(add)
 			continue
 		}