Rails server fails to start in Discourse project either in development or production. Below are the logs when trying to start the server in dev mode. The application was installed and has been working, It's deployed on AWS in production mode and restarting the unicorn loads the application for some time and again the url stops responding with error messages.
Development logs from $rails s
rb t@ip-XXX-XX-XX-XX-app:/var/www/discourse# vi
config/environments/development.r
root@ip-172-31-25-46-app:/var/www/discourse# rails s
=> Booting Puma
=> Rails 5.1.4 application starting in production
=> Run `rails server -h` for more startup options
Exiting
bundler: failed to load command: script/rails (script/rails)
Redis::CommandError: ERR Error running script (call to f_b06356ba4628144e123b652c99605b873107c9be): @user_script:14: @user_script: 14: -MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.
/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis/client.rb:121:in `call'
/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis.rb:2399:in `block in _eval'
/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis.rb:58:in `block in synchronize'
/usr/local/lib/ruby/2.4.0/monitor.rb:214:in `mon_synchronize'
/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis.rb:58:in `synchronize'
/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis.rb:2398:in `_eval'
/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis.rb:2450:in `evalsha'
/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/message_bus-2.1.1/lib/message_bus/backends/redis.rb:380:in `cached_eval'
/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/message_bus-2.1.1/lib/message_bus/backends/redis.rb:140:in `publish'
/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/message_bus-2.1.1/lib/message_bus.rb:248:in `publish'
/var/www/discourse/lib/distributed_cache.rb:72:in `publish'
**Production logs **
/var/www/discourse/lib/demon/base.rb:109:in `ensure_running'
/var/www/discourse/lib/demon/base.rb:34:in `block in ensure_running'
/var/www/discourse/lib/demon/base.rb:33:in `each'
/var/www/discourse/lib/demon/base.rb:33:in `ensure_running'
config/unicorn.conf.rb:145:in `master_sleep'
/var/www/discourse/vendor/bundle/ruby/2.3.0/gems/unicorn-5.1.0/lib/unicorn/http_server.rb:284:in `join'
/var/www/discourse/vendor/bundle/ruby/2.3.0/gems/unicorn-5.1.0/bin/unicorn:126:in `<top (required)>'
/var/www/discourse/vendor/bundle/ruby/2.3.0/bin/unicorn:23:in `load'
/var/www/discourse/vendor/bundle/ruby/2.3.0/bin/unicorn:23:in `<main>'
E, [2018-01-04T08:43:37.949928 #60] ERROR -- : reaped #<Process::Status: pid 5870 exit 1> worker=unknown
Detected dead worker 5870, restarting...
Loading Sidekiq in process id 5883
Failed to report error: MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error. 4 Redis::CommandError (MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.)
/var/www/discourse/vendor/bundle/ruby/2.3.0/gems/redis-3.3.0/lib/redis/client.rb:121:in `call' web-exception
Redis logs
47:M 17 Jan 09:38:01.070 # Can't save in background: fork: Cannot allocate memory
47:M 17 Jan 09:38:07.087 * 10000 changes in 60 seconds. Saving...
The issue has been fixed, Edited this file
/etc/sysctl.conf and added the line at last
vm.overcommit_memory=1
After this restarted sysctl.
$ sudo sysctl -p /etc/sysctl.conf
Redis doesn't need the amount of memory which OS thinks, the status 1 means always overcommit, never check. More details can be found from Redis Docs.