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Tag: exceptions (page 2 of 2)

Adding reentrancy and a on failure fallback for your Sidekiq workers

Few months ago I’ve created a post about reentrancy: Ruby (Rails, Sinatra) background processing – Reentrancy for your workers is a must be!.

In this post, I will present a nice way to implement such feature for your Sidekiq workers.

Simple reentrancy

Normally a Sidekiq worker looks similar to this one:

class ExampleWorker
  include Sidekiq::Worker

  def perform(*args)
    # Background logic here
  end
end

and if something goes wrong, you should see it in your Sidekiq log (or a bugtracker like Errbit). However there is no reentrancy there. You could catch exceptions and handle reentrancy with this code:

class ExampleWorker
  include Sidekiq::Worker

  def perform(*args)
    # Background logic here
  rescue => exception
    # Do something on failure before reraising
    raise exception
  end
end

but it is not too elegant and if you have multiple Sidekiq workers, than probably you will end-up with a lot of code duplication.

Making your reentrancy code more fancy

Instead of handling reentrancy in every single worker, you could just create a base worker class, that would provide such functionality for all the workers that would inherit from the base one:

class BaseWorker
  include Sidekiq::Worker

  def perform(*args)
    # you need to implement the execute method
    # execute method should contain code you want to execute in the background
    execute(*args)
  rescue => exception
    after_failure(*args) if respond_to?(:after_failure)
    raise exception
  end
end

Now, instead of implementing a perform method in every worker, you need to name it (or rename) execute. Perform method will act as a wrapper that will try to execute your worker code and if it fails, will run the after_failure method (if it exists).

Note that the error will be reraised, but now we have a fallback to do for example some database status changes.

class KeywordsWorker < BaseWorker
  def execute(keyword_name)
    KeywordsService.new.remotely(keyword_name)
  end

  # Bring to an expire state if something goes wrong
  def after_failure(keyword_name)
    KeywordsService.new.expire(keyword_name)
  end
end

Of course we might have workers, that won’t require reentrancy at all. Then we just skip the after_failure method and thanks to the respond_to? method, everything will work normally.

Errbit + HTTPS: Setting up Errbit reporter (Airbrake v4 gem) to work with self-signed HTTPS Errbit

Warning: This post is outdated and this fix will work only with old Airbrake version (v4) – it does not work with the v4 version of Airbrake notifier. If you’re looking for a solution for Airbrake v5, please refere to this post: Errbit + HTTPS: Setting up Errbit reporter (Airbrake v5 gem) to work with self-signed HTTPS certificate

Having an error catcher like Errbit behind SSL is generally a good idea. Especially when Errbit is hosted on a different server than you application (for example when you manage multiple apps with one Errbit instance). In many cases you will have a self-signed certificate (why would you pay for a cert for internal tool). If you try to use it with Airbrake, you will see following error:

2.1.0 :002 &gt; Airbrake.notify Exception.new('test')
** [Airbrake] Unable to contact the Airbrake server. HTTP Error=SSL_connect 
   returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed
** [Airbrake] Environment Info: [Ruby: 2.1.0] [Rails: 4.0.4] [Env: production]
** [Airbrake] Failure: NilClass
** [Airbrake] Environment Info: [Ruby: 2.1.0] [Rails: 4.0.4] [Env: production]
** [Airbrake] Notice details: 
  exception: test
  api_key: key
  backtrace: (irb):2:in `irb_binding'
/lib/ruby/2.1.0/irb/workspace.rb:86:in `eval'
/lib/ruby/2.1.0/irb/workspace.rb:86:in `evaluate'
/lib/ruby/2.1.0/irb/context.rb:380:in `evaluate'
/lib/ruby/2.1.0/irb.rb:492:in `block (2 levels) in eval_input'
/lib/ruby/2.1.0/irb.rb:624:in `signal_status'
/lib/ruby/2.1.0/irb.rb:489:in `block in eval_input'
/lib/ruby/2.1.0/irb/ruby-lex.rb:247:in `block (2 levels) in each_top_level_statement'
/lib/ruby/2.1.0/irb/ruby-lex.rb:233:in `loop'
/lib/ruby/2.1.0/irb/ruby-lex.rb:233:in `block in each_top_level_statement'
/lib/ruby/2.1.0/irb/ruby-lex.rb:232:in `catch'
/lib/ruby/2.1.0/irb/ruby-lex.rb:232:in `each_top_level_statement'
/lib/ruby/2.1.0/irb.rb:488:in `eval_input'
/lib/ruby/2.1.0/irb.rb:397:in `block in start'
/lib/ruby/2.1.0/irb.rb:396:in `catch'
/lib/ruby/2.1.0/irb.rb:396:in `start'
[GEM_ROOT]/gems/railties-4.0.4/lib/rails/commands/console.rb:90:in `start'
[GEM_ROOT]/gems/railties-4.0.4/lib/rails/commands/console.rb:9:in `start'
[GEM_ROOT]/gems/railties-4.0.4/lib/rails/commands.rb:62:in `&lt;top (required)&gt;'
bin/rails:4:in `require'
bin/rails:4:in `&lt;main&gt;'

In order to make it work you need to disable SSL verification for Ruby:

OpenSSL::SSL::VERIFY_PEER = OpenSSL::SSL::VERIFY_NONE

Of course keep in mind, that it will disable SSL verification for all other libs as well.

Whole Errbit config should look like this:

Airbrake.configure do |config|
  config.api_key = 'api_key'
  config.host    = 'errbit.domain'
  config.port    = 443
  config.secure  = true
  config.ignore_only = ['ActiveRecord::RecordNotFound']
end if Rails.env.production?

OpenSSL::SSL::VERIFY_PEER = OpenSSL::SSL::VERIFY_NONE
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