Safety nets for your Ruby daemons

Daemon-kit has been getting a lot of TLC from me lately, and it’s not going to stop anytime soon. As I wander deeper and deeper into AMQP territory, I need to extend daemon-kit to cope with all kinds of new scenarios. One of those being unhandled exceptions.

The second thing I put on the TODO list was Rails-style exception handling. With version 0.1.6 there has been some progress made in that regard. Daemon-kit now sports a configurable safety net for dangerous code. By wrapping blocks of code in a “safety net”, unhandled exceptions are caught and logged, and optionally sent via email or to Hoptoad for review.

Hoptoad? In a Ruby daemon? Sure, inspiration came via these tweets.

And it only makes sense to do it. Now for some code:

safely do
  # do something silly
  silly.action!
end

safely is mixed into Object and can be used freely. It is important to note that you have to handle your daemon-specific applications on your own and rely on safely as a fall over mechanism.

To configure the safety net, you can edit your config/environment.rb file and add the following lines to the configure block:

# for email notifications
config.safety_net.handler = :mail
config.safety_net.mail.recipients = ['you@gmail.com']

# for hoptoad
config.safety_net.handler = :hoptoad
config.safety_net.hoptoad.api_key = 'your-hoptoad-key'

The documentation is very rough at the moment, but the files you want to explore are lib/daemon_kit/safety.rb and the error handlers in lib/daemon_kit/error_handlers.

NOTE: If you are upgrading from an earlier daemon-kit, please upgrade your daemons as well by running the following rake task in the root of your daemon projects:

$ rake daemon_kit:upgrade

In the coming days/weeks you can look forward to the following enhancements as well:

I’m patching things up as I go along, adding features as I need them (and stuff I recall from my first daemons). There is still a lot of things that need attention, but they’ll be addressed and hopefully daemon-kit grows to becoming the premier framework for writing daemon processes in our beloved Ruby.

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