After configured external Redis, system-sphinx throws errors repeatedly.

Issue

• Following this solution, I configured external Redis to 3scale on-premises. After that, system-sphinx container outputs this error repeatedly

  [2018-12-26 09:50:07.326] Name or service not known subscribe failed, reconnecting in 1 second. Call stack ["/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/connection/hiredis.rb:17:in `connect'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/connection/hiredis.rb:17:in `connect'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:323:in `establish_connection'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:94:in `block in connect'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:280:in `with_reconnect'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:93:in `connect'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:263:in `with_socket_timeout'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:274:in `without_socket_timeout'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/client.rb:126:in `call_loop'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/subscribe.rb:35:in `subscription'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis/subscribe.rb:12:in `subscribe'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis.rb:2718:in `_subscription'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis.rb:2098:in `block in subscribe'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis.rb:57:in `block in synchronize'", "/opt/rh/rh-ruby23/root/usr/share/ruby/monitor.rb:214:in `mon_synchronize'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis.rb:57:in `synchronize'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/redis-3.2.2/lib/redis.rb:2097:in `subscribe'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/message_bus-2.0.2/lib/message_bus/backends/redis.rb:304:in `global_subscribe'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/message_bus-2.0.2/lib/message_bus.rb:513:in `global_subscribe_thread'", "/opt/system/vendor/bundle/ruby/2.3.0/gems/message_bus-2.0.2/lib/message_bus.rb:461:in `block in new_subscriber_thread'"]