ActionCable Timeout - "Idle Connection" on Heroku

Question

ActionCable Timeout - "Idle Connection" on Heroku

We have been using ActionCable on Heroku for some time, and overall it works well. However, we see the H15 Idle Connection error many times a day. They always have path=/cable and a long service time, so the connection was definitely lively and healthy for a while.

 Dec 2016 08:32:22.057 heroku router - - at=error code=H15 desc="Idle connection" method=GET path="/cable" host=<our host> dyno=web.2 connect=1ms service=928755ms status=503

I believe that our configuration is very standard and closely follows the Rails docs for ActionCable:

 module ApplicationCable class Connection < ActionCable::Connection::Base identified_by :current_user def connect self.current_user = find_verified_user end protected def find_verified_user if current_user = User.find_by(id: cookies.signed[:user_id]) current_user else # reject_unauthorized_connection end end end end

We have three simple channels:

 class ActivitiesChannel < ApplicationCable::Channel def subscribed stream_from "activities_#{current_user.id}" if current_user end end

Edit to add - Javascript code:

app/assets/javascripts/channels/setup.js :

 //= require cable this.App || (this.App = {}); App.cable = ActionCable.createConsumer();

app/assets/javascripts/channels/notifications.js :

 App.notifications = App.cable.subscriptions.create('NotificationsChannel', { received: function(data) { return this.showMessage(data); }, showMessage: function(data) { showNotice(data.message); } });