ruby on rails - Sidekiq job is scheduled, not running and just disappears -

i'm working on rails application sends emails in background using sidekiq , mandrill. in application have 2 queues, 1 user interactions service (irrelevant) , second mailer queue. mailer queue used 2 mailers: 1 managing user profile , other 1 interactions our service (irrelevant).

today noticed users not getting emails few days except confirmation email sent devise.

the other queue working flawlessly , doesn't have problems. (so maybe sidekiq configuration not problem).

for example lets take usermailer notifies user of successful profile update:

user_mailer.rb

def update_user(user)     @user = user     mail(:to => user.email) end 

user_profile_controller.rb

  def update_resource(user)     user.save     usermailer.update_user(user).deliver_later(wait: 1.minute)   end 

when tried testing function deliver_now instead of deliver_later worked , mail sent (so connection mandrill working). when test function is, job being added mailer queue. when it's time send email disappears queue without sending email , without leaving exceptions in logs.

i can see appear in sidekiq web ui , disappear.

i guess confirmation email 1 being sent because isn't delayed, don't know why happenning.

everything working great on staging environment. difference it's working mailtrap , doesn't have jobs production.

some code might relevant:

production.rb

 config.action_mailer.delivery_method = :smtp   config.action_mailer.smtp_settings = {       :user_name => 'xxx',       :password => rails.application.secrets.smtp_password,       :address => 'smtp.mandrillapp.com',       :domain => config.app_domain,       :port => 'xxx',       :authentication => :login   } ...  config.action_mailer.default_url_options = { :host => config.app_domain, :protocol => 'https' }   config.action_mailer.perform_deliveries = true   config.action_mailer.raise_delivery_errors = false 

application.rb

config.active_job.queue_adapter = :sidekiq 

walked through these links without solution:

http://guides.rubyonrails.org/active_job_basics.html http://api.rubyonrails.org/classes/actionmailer/base.html

haven't found other links relevant issue.

• tried re-deploying
• tried restarting sidekiq
• tried restarting redis
• tried restarting server itself
• tried sending email console - successful
• tried sending email deliver_later(wait:1min) - unsuccessful

i'm suspecting has lack of memory on server. when increased memory on server , max_connections parameter on postgres, emails on queue supposed sent, delivered immediately