Puma server stop by ThreadError (deadlock; recursive locking) - ruby-on-rails

Question

I'm running mastodon in server(1 core, 4GB RAM).
It sometimes happens deadrock and server error.
I could not find out when to happen this error, but it did multiple times.
A temporary solution is restarting server for now.
What are causes happening this issue? and How to solve it?
Error Log
vendor/bundle/ruby/2.5.0/gems/rack-2.0.3/lib/rack/session/abstract/id.rb:226:in `call'
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/cookies.rb:613:in `call'
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/callbacks.rb:26:in `block in
/home/mastodon/.rbenv/versions/2.5.0/lib/ruby/2.5.0/delegate.rb:83:in `method_missing'
vendor/bundle/ruby/2.5.0/gems/rack-attack-5.0.1/lib/rack/attack/store_proxy/redis_store_proxy.rb:31:in `in
vendor/bundle/ruby/2.5.0/gems/rack-attack-5.0.1/lib/rack/attack/cache.rb:49:in `do_count'
vendor/bundle/ruby/2.5.0/gems/rack-attack-5.0.1/lib/rack/attack/cache.rb:19:in `count'
vendor/bundle/ruby/2.5.0/gems/rack-attack-5.0.1/lib/rack/attack/throttle.rb:27:in `[]'
vendor/bundle/ruby/2.5.0/gems/rack-attack-5.0.1/lib/rack/attack.rb:89:in `block in throttled?'
vendor/bundle/ruby/2.5.0/gems/rack-attack-5.0.1/lib/rack/attack.rb:88:in `any?'
vendor/bundle/ruby/2.5.0/gems/rack-attack-5.0.1/lib/rack/attack.rb:88:in `throttled?'
vendor/bundle/ruby/2.5.0/gems/rack-attack-5.0.1/lib/rack/attack.rb:143:in `call'
vendor/bundle/ruby/2.5.0/gems/warden-1.2.7/lib/warden/manager.rb:36:in `block in call'
vendor/bundle/ruby/2.5.0/gems/warden-1.2.7/lib/warden/manager.rb:35:in `catch'
vendor/bundle/ruby/2.5.0/gems/warden-1.2.7/lib/warden/manager.rb:35:in `call'
vendor/bundle/ruby/2.5.0/gems/rack-2.0.3/lib/rack/etag.rb:25:in `call'
vendor/bundle/ruby/2.5.0/gems/rack-2.0.3/lib/rack/conditional_get.rb:25:in `call'
vendor/bundle/ruby/2.5.0/gems/rack-2.0.3/lib/rack/head.rb:12:in `call'
vendor/bundle/ruby/2.5.0/gems/rack-2.0.3/lib/rack/session/abstract/id.rb:232:in `context'
vendor/bundle/ruby/2.5.0/gems/rack-2.0.3/lib/rack/session/abstract/id.rb:226:in `call'
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/cookies.rb:613:in `call'
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/callbacks.rb:26:in `block in
vendor/bundle/ruby/2.5.0/gems/activesupport-5.1.4/lib/active_support/callbacks.rb:97:in `run_callbacks'
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/callbacks.rb:24:in `call'
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/debug_exceptions.rb:59:in `c
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/show_exceptions.rb:31:in `ca
vendor/bundle/ruby/2.5.0/gems/lograge-0.7.1/lib/lograge/rails_ext/rack/logger.rb:15:in `call_app'
vendor/bundle/ruby/2.5.0/gems/railties-5.1.4/lib/rails/rack/logger.rb:24:in `block in call'
vendor/bundle/ruby/2.5.0/gems/activesupport-5.1.4/lib/active_support/tagged_logging.rb:69:in `block in tag
vendor/bundle/ruby/2.5.0/gems/activesupport-5.1.4/lib/active_support/tagged_logging.rb:26:in `tagged'
vendor/bundle/ruby/2.5.0/gems/activesupport-5.1.4/lib/active_support/tagged_logging.rb:69:in `tagged'
vendor/bundle/ruby/2.5.0/gems/railties-5.1.4/lib/rails/rack/logger.rb:24:in `call'
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/remote_ip.rb:79:in `call'
vendor/bundle/ruby/2.5.0/gems/request_store-1.3.2/lib/request_store/middleware.rb:9:in `call'
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/request_id.rb:25:in `call'
vendor/bundle/ruby/2.5.0/gems/rack-2.0.3/lib/rack/method_override.rb:22:in `call'
vendor/bundle/ruby/2.5.0/gems/rack-2.0.3/lib/rack/runtime.rb:22:in `call'
vendor/bundle/ruby/2.5.0/gems/rack-timeout-0.4.2/lib/rack/timeout/core.rb:122:in `block in call'
vendor/bundle/ruby/2.5.0/gems/rack-timeout-0.4.2/lib/rack/timeout/support/timeout.rb:19:in `timeout'
vendor/bundle/ruby/2.5.0/gems/rack-timeout-0.4.2/lib/rack/timeout/core.rb:121:in `call'
vendor/bundle/ruby/2.5.0/gems/actionpack-5.1.4/lib/action_dispatch/middleware/executor.rb:12:in `call'
vendor/bundle/ruby/2.5.0/gems/rack-2.0.3/lib/rack/sendfile.rb:111:in `call'
vendor/bundle/ruby/2.5.0/gems/rack-cors-0.4.1/lib/rack/cors.rb:81:in `call'
vendor/bundle/ruby/2.5.0/gems/railties-5.1.4/lib/rails/engine.rb:522:in `call'
vendor/bundle/ruby/2.5.0/gems/puma-3.11.0/lib/puma/configuration.rb:225:in `call'
vendor/bundle/ruby/2.5.0/gems/puma-3.11.0/lib/puma/server.rb:624:in `handle_request'
vendor/bundle/ruby/2.5.0/gems/puma-3.11.0/lib/puma/server.rb:438:in `process_client'
vendor/bundle/ruby/2.5.0/gems/puma-3.11.0/lib/puma/server.rb:302:in `block in run'
vendor/bundle/ruby/2.5.0/gems/puma-3.11.0/lib/puma/thread_pool.rb:120:in `block in spawn_thread'
method=GET path=/ format=html controller=HomeController action=index status=401 duration=18.72 view=0.00 d
ThreadError (deadlock; recursive locking):
app/models/setting.rb:26:in `[]'
Config file and env variables
#Puma server settings
WEB_CONCURRENCY=0
MAX_THREADS=5
config/puma.rb
threads_count = ENV.fetch('MAX_THREADS') { 5 }.to_i
threads threads_count, threads_count
if ENV['SOCKET'] then
bind 'unix://' + ENV['SOCKET']
else
port ENV.fetch('PORT') { 3000 }
end
environment ENV.fetch('RAILS_ENV') { 'development' }
workers ENV.fetch('WEB_CONCURRENCY') { 0 }
preload_app!
on_worker_boot do
ActiveRecord::Base.establish_connection if defined?(ActiveRecord)
end
plugin :tmp_restart
Thank you in advance.

Answer 1

For me, it was a ruby issue. I was using the wrong version of ruby and I changed the ruby version and it started working after that.
to check the ruby version do:
ruby -v
to change ruby version using rvm
rvm use 2.6.3