From 917ce27a2c51cd05d19ad9c96cc2ed14bc98a8fe Mon Sep 17 00:00:00 2001
From: Henry Oswald <henry.oswald@sharelatex.com>
Date: Thu, 20 Nov 2014 12:50:19 +0000
Subject: [PATCH] add a double message check

---
 libraries/redis-wrapper/index.coffee | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libraries/redis-wrapper/index.coffee b/libraries/redis-wrapper/index.coffee
index 386765af38..770a5030d0 100644
--- a/libraries/redis-wrapper/index.coffee
+++ b/libraries/redis-wrapper/index.coffee
@@ -26,6 +26,7 @@ module.exports = RedisSharelatex =
 		pub = RedisSharelatex.createClient(connectionInfo)
 		
 		redisIsOk = true
+		lastPingMessage = ""
 		heartbeatInterval = 2000 #ms
 		isAliveTimeout = 10000 #ms
 		
@@ -37,11 +38,15 @@ module.exports = RedisSharelatex =
 			if error?
 				console.error "ERROR: failed to subscribe to #{heartbeatChannel} channel", error
 		sub.on "message", (channel, message) ->
+			if lastPingMessage == message #we got the same message twice
+				redisIsOk = false
+			lastPingMessage = message
 			if channel == heartbeatChannel
 				lastHeartbeat = Date.now()
 		
 		setInterval ->
-			pub.publish heartbeatChannel, "PING"
+			message = "ping:#{Date.now()}"
+			pub.publish heartbeatChannel, message
 		, heartbeatInterval
 
 		isAlive = ->