問題

トリガーするとError connecting to Redis on localhost:6379 (Errno::ECONNREFUSED) (Redis::CannotConnectError)でアプリケーションが落ちてしまう。

/path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:332:in `rescue in establish_connection': Error connecting to Redis on localhost:6379 (Errno::ECONNREFUSED) (Redis::CannotConnectError)
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:318:in `establish_connection'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:94:in `block in connect'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:280:in `with_reconnect'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:93:in `connect'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:351:in `ensure_connected'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:208:in `block in process'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:293:in `logging'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:207:in `process'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:113:in `call'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis.rb:2085:in `block in publish'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis.rb:57:in `block in synchronize'
	from /Users/hirokishirai/.rbenv/versions/2.3.0/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis.rb:57:in `synchronize'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis.rb:2084:in `publish'
	from /path_to_app_dir/vendor/bundle/ruby/2.3.0/gems/websocket-rails-0.7.0/lib/websocket_rails/synchronization.rb:63:in `block in publish'

２つの解決策

どちらも動作確認済みです。
moaaさんのfixesをそのまま使っちゃうか、とりあえずredisを3.2.0にダウングレードしてwebsocket-railのマスターにfixesがマージされるのを待つかです。どちらでも良いと思います。

方法１ `moaa/websocket-rails`の`sync_fixes`ブランチを使う

Gemfileを次のように書き換える

- gem 'websocket-rails'
+ gem 'websocket-rails', github: 'moaa/websocket-rails', branch: 'sync_fixes'

方法２ `gem 'redis'`のバージョンを`3.2.0`にダウングレードする

Gemfileを次のように書き換える

- gem 'redis'
+ gem 'redis', '3.2.0'

redisをupdate（Gemfile.lockでバージョンがロックされているのでbundle installは通らないはず）

bundle update redis

Source↓

Redis error when sending two different messages · Issue #313 · websocket-rails/websocket-rails