Heroku worker throwing errors when activated?

Question

I got a simple and free heroku app running where I added redis/sidekiq in order to send out mails in the background. I set everything up and once I start the worker, I get following error message in a loop:

Error fetching job: ERR max number of clients reached
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:114:in `call'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:95:in `block in connect'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:280:in `with_reconnect'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:93:in `connect'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:351:in `ensure_connected'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:208:in `block in process'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:293:in `logging'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:207:in `process'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:113:in `call'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:196:in `block in call_with_timeout'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:267:in `with_socket_timeout'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis/client.rb:195:in `call_with_timeout'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis.rb:1097:in `block in _bpop'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis.rb:57:in `block in synchronize'
/app/vendor/ruby-2.2.2/lib/ruby/2.2.0/monitor.rb:211:in `mon_synchronize'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis.rb:57:in `synchronize'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis.rb:1094:in `_bpop'
/app/vendor/bundle/ruby/2.2.0/gems/redis-3.2.2/lib/redis.rb:1139:in `brpop'
/app/vendor/bundle/ruby/2.2.0/gems/redis-namespace-1.5.2/lib/redis/namespace.rb:393:in `call_with_namespace'
/app/vendor/bundle/ruby/2.2.0/gems/redis-namespace-1.5.2/lib/redis/namespace.rb:290:in `method_missing'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq/fetch.rb:35:in `block in retrieve_work'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq.rb:84:in `block in redis'
/app/vendor/bundle/ruby/2.2.0/gems/connection_pool-2.2.0/lib/connection_pool.rb:64:in `block (2 levels) in with'
/app/vendor/bundle/ruby/2.2.0/gems/connection_pool-2.2.0/lib/connection_pool.rb:63:in `handle_interrupt'
/app/vendor/bundle/ruby/2.2.0/gems/connection_pool-2.2.0/lib/connection_pool.rb:63:in `block in with'
/app/vendor/bundle/ruby/2.2.0/gems/connection_pool-2.2.0/lib/connection_pool.rb:60:in `handle_interrupt'
/app/vendor/bundle/ruby/2.2.0/gems/connection_pool-2.2.0/lib/connection_pool.rb:60:in `with'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq.rb:81:in `redis'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq/fetch.rb:35:in `retrieve_work'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq/processor.rb:85:in `get_one'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq/processor.rb:95:in `fetch'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq/processor.rb:78:in `process_one'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq/processor.rb:67:in `run'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq/util.rb:16:in `watchdog'
/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.0.1/lib/sidekiq/util.rb:24:in `block in safe_thread'

sidekiq.yml:

---
:queues:
  - default
  - mailers

sidekiq.rb:

Sidekiq.configure_server do |config|
  config.redis = { :namespace => "mynamespace" }
end

Sidekiq.configure_client do |config|
  config.redis = { :namespace => "mynamespace" }
end

require "sidekiq/web"
Sidekiq::Web.app_url = "/"
Sidekiq::Web.use(Rack::Auth::Basic, "Application") do |username, password|
  username == ENV.fetch("SIDEKIQ_WEB_USERNAME") &&
  password == ENV.fetch("SIDEKIQ_WEB_PASSWORD")
end

Anyone an idea what's wrong here? If you need any further info on the config files or something, let me know.

Answer 1

This was the best solution that I found. If you are using the free heroku plan and the free redis nano plan. All the connections have to add up to 10 or less. To make sure that the connections add up check out this blog post. http://manuelvanrijn.nl/blog/2012/11/13/sidekiq-on-heroku-with-redistogo-nano/

He explains how everything adds up.

The writer also has a calculator that will help to calculate what the configuration should be for your particular server, sidekiq etc. It also tells you where the information needs to be added. I was stuck on this too hope it saves somebody some time :)

Answer 2

Changing sidekiq.yml to

---
:queues:
  - default
  - mailers
:concurrency: 5

did the trick. Setting concurrency to 9 did not for some reason even though heroku allows 10 for the redis nano addon.