Anycable (the 1 year return) (#1019)

* Resurrect / un-revert anycable changes 

- Original PR was #457

Author: kaptron

Gemfile

@@ -9,7 +9,7 @@ end
 # NOTE: IMPORTANT for this to be first so that gems e.g. omniauth-ideo
 #       can pull in the right ENV vars
 # ENV variables in dev
-gem 'dotenv-rails', require: 'dotenv/rails-now'
+gem 'dotenv-rails', groups: %i[development test], require: 'dotenv/rails-now'
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.2'
@@ -147,6 +147,11 @@ gem 'schmooze', require: false
 # Faker needed for generating fake names
 gem 'faker', '~> 1.9.5'
 
+# Anycable for more performant ActionCable
+# Note: you must `brew install anycable-go` if you want to run it locally
+# See: https://docs.anycable.io/#/using_with_rails
+gem 'anycable-rails', '>= 0.6.2'
+
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
   gem 'byebug', platforms: %i[mri mingw x64_mingw]

Gemfile.lock

@@ -92,6 +92,13 @@ GEM
     annotate (2.7.5)
       activerecord (>= 3.2, < 7.0)
       rake (>= 10.4, < 13.0)
+    anycable (0.6.4)
+      anyway_config (~> 1.4.2)
+      grpc (~> 1.17)
+    anycable-rails (0.6.5)
+      anycable (~> 0.6.0)
+      rails (>= 5)
+    anyway_config (1.4.4)
     appsignal (2.5.1)
       rack
     arel (9.0.0)
@@ -591,6 +598,7 @@ DEPENDENCIES
   acts-as-taggable-on (~> 6.0.0)
   amoeba
   annotate
+  anycable-rails (>= 0.6.2)
   appsignal
   autoprefixer-rails
   barnes

Procfile

@@ -1,3 +1,3 @@
-web: bundle exec puma -C config/puma.rb
+web: ANYCABLE_REDIS_URL=$REDIS_URL REDIS=$REDIS_URL bin/heroku-web
 release: bundle exec rake db:migrate
 worker: bundle exec sidekiq -e ${RACK_ENV:-development} -C config/sidekiq.yml

app/channels/application_cable/channel.rb

@@ -1,6 +1,16 @@
 module ApplicationCable
   class Channel < ActionCable::Channel::Base
+    after_subscribe :track_user
+    after_unsubscribe :untrack_user
     delegate :current_ability, to: :connection
     protected :current_ability
+
+    def track_user
+      ChannelPresenceTracker.track(self.class.name, current_user.id)
+    end
+
+    def untrack_user
+      ChannelPresenceTracker.untrack(self.class.name, current_user.id)
+   end
   end
 end

app/channels/application_cable/connection.rb

@@ -3,7 +3,7 @@ class Connection < ActionCable::Connection::Base
     identified_by :current_user
 
     def connect
-      self.current_user = find_verified_user
+      self.current_user = find_verified_user || reject_unauthorized_connection
     end
 
     def current_ability
@@ -13,7 +13,11 @@ def current_ability
     private
 
     def find_verified_user
-      env['warden'].user
+      app_cookies_key = Rails.application.config.session_options[:key] ||
+                        raise('Anycable: no session cookies key in config')
+
+      env['rack.session'] = cookies.encrypted[app_cookies_key]
+      Warden::SessionSerializer.new(env).fetch(:user)
     end
   end
 end

app/models/app_metric.rb

@@ -0,0 +1,18 @@
+# == Schema Information
+#
+# Table name: app_metrics
+#
+#  id         :bigint(8)        not null, primary key
+#  metric     :string
+#  value      :float
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+# Indexes
+#
+#  index_app_metrics_on_metric_and_created_at  (metric,created_at)
+#
+
+class AppMetric < ApplicationRecord
+  validates :metric, :value, presence: true
+end

app/services/channel_presence_tracker.rb

@@ -0,0 +1,20 @@
+class ChannelPresenceTracker
+  CACHE_KEY = 'channel_subcriptions'.freeze
+  cattr_accessor :redis_client
+
+  def self.client
+    self.redis_client ||= Redis.new(url: ENV['REDIS_URL'])
+  end
+
+  def self.current_subscriptions
+    client.smembers(CACHE_KEY)
+  end
+
+  def self.track(channel_name, user_id)
+    client.sadd(CACHE_KEY, "#{channel_name}-#{user_id}")
+  end
+
+  def self.untrack(channel_name, user_id)
+    client.srem(CACHE_KEY, "#{channel_name}-#{user_id}")
+  end
+end

app/workers/log_channel_subscribers_worker.rb

@@ -0,0 +1,27 @@
+class LogChannelSubscribersWorker
+  include Sidekiq::Worker
+
+  def perform
+    create_app_metrics
+  end
+
+  private
+
+  def create_app_metrics
+    subscriptions_by_channel.each do |channel_name, count|
+      AppMetric.create(
+        metric: "subscribers-#{channel_name}",
+        value: count,
+      )
+    end
+  end
+
+  def subscriptions_by_channel
+    subscriptions = ChannelPresenceTracker.current_subscriptions
+    subscriptions.each_with_object({}) do |key, h|
+      channel_key, _user_id = key.to_s.split('-')
+      h[channel_key] ||= 0
+      h[channel_key] += 1
+    end
+  end
+end

bin/heroku-web

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+if [ "$ANYCABLE_DEPLOYMENT" == "true" ]; then
+  bundle exec anycable --server-command="anycable-go"
+else
+  bundle exec puma -C config/puma.rb
+fi

config/anycable.yml

@@ -0,0 +1,5 @@
+production:
+  # production ANYCABLE_REDIS_URL is set via Procfile to $REDIS_URL
+  access_logs_disabled: false
+development:
+  redis_url: redis://localhost:6379/1