From d3b9eea23a3d84e36230d6eaaa74aac915bdb3a1 2014-09-14 22:22:05
From: Richard Everson <R.M.Everson@exeter.ac.uk>
Date: 2014-09-14 22:22:05
Subject: [PATCH] Check time of last ping before timing out a missing pong.

---

diff --git a/IPython/html/base/zmqhandlers.py b/IPython/html/base/zmqhandlers.py
index 1569bca..768e544 100644
--- a/IPython/html/base/zmqhandlers.py
+++ b/IPython/html/base/zmqhandlers.py
@@ -109,6 +109,7 @@ WS_PING_INTERVAL = 30000
 
 class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler):
     ping_callback = None
+    last_ping = 0
     last_pong = 0
     
     @property
@@ -151,7 +152,8 @@ class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler):
         
         # start the pinging
         if self.ping_interval > 0:
-            self.last_pong = ioloop.IOLoop.instance().time()
+            self.last_ping = ioloop.IOLoop.instance().time()  # Remember time of last ping
+            self.last_pong = self.last_ping
             self.ping_callback = ioloop.PeriodicCallback(self.send_ping, self.ping_interval)
             self.ping_callback.start()
 
@@ -161,15 +163,19 @@ class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler):
             self.ping_callback.stop()
             return
         
-        # check for timeout on pong
-        since_last_pong = 1e3 * (ioloop.IOLoop.instance().time() - self.last_pong)
-        if since_last_pong > self.ping_timeout:
+        # check for timeout on pong.  Make sure that we really have sent a recent ping in
+        # case the machine with both server and client has been suspended since the last ping.
+        now = ioloop.IOLoop.instance().time()
+        since_last_pong = 1e3 * (now - self.last_pong)
+        since_last_ping = 1e3 * (now - self.last_ping)
+        if since_last_ping < 2*self.ping_interval and since_last_pong > self.ping_timeout:
             self.log.warn("WebSocket ping timeout after %i ms.", since_last_pong)
             self.close()
             return
 
         self.ping(b'')
-    
+        self.last_ping = now
+
     def on_pong(self, data):
         self.last_pong = ioloop.IOLoop.instance().time()