1 files changed, 65 insertions, 0 deletions
diff --git a/lib/assets/javascripts/cable/connection_monitor.js.coffee b/lib/assets/javascripts/cable/connection_monitor.js.coffee
new file mode 100644
index 0000000000..fc5093c5eb
--- /dev/null
+++ b/lib/assets/javascripts/cable/connection_monitor.js.coffee
@@ -0,0 +1,65 @@
+class Cable.ConnectionMonitor
+  identifier: Cable.PING_IDENTIFIER
+
+  pollInterval:
+    min: 2
+    max: 30
+
+  staleThreshold:
+    startedAt: 4
+    pingedAt: 8
+
+  constructor: (@consumer) ->
+    @consumer.subscribers.add(this)
+    @start()
+
+  connected: ->
+    @reset()
+    @pingedAt = now()
+
+  received: ->
+    @pingedAt = now()
+
+  reset: ->
+    @reconnectAttempts = 0
+
+  start: ->
+    @reset()
+    delete @stoppedAt
+    @startedAt = now()
+    @poll()
+
+  stop: ->
+    @stoppedAt = now()
+
+  poll: ->
+    setTimeout =>
+      unless @stoppedAt
+        @reconnectIfStale()
+        @poll()
+    , @getInterval()
+
+  getInterval: ->
+    {min, max} = @pollInterval
+    interval = 4 * Math.log(@reconnectAttempts + 1)
+    clamp(interval, min, max) * 1000
+
+  reconnectIfStale: ->
+    if @connectionIsStale()
+      @reconnectAttempts += 1
+      @consumer.connection.reopen()
+
+  connectionIsStale: ->
+    if @pingedAt
+      secondsSince(@pingedAt) > @staleThreshold.pingedAt
+    else
+      secondsSince(@startedAt) > @staleThreshold.startedAt
+
+  now = ->
+    new Date().getTime()
+
+  secondsSince = (time) ->
+    (now() - time) / 1000
+
+  clamp = (number, min, max) ->
+    Math.max(min, Math.min(max, number))