Verify Database Connections in Long-Running Idle Rails Processes

I recently interfaced one of my xmpp4r bots with the Xeriom Networks control panel. I’d planned to write a post about how easy it is, but RubyPond beat me to it. I can, however, offer one piece of advice that will save you from a subtle bug: periodically verify your database connections.

If your Rails process sits idle for a while, which is normal for something like a chat bot waiting for messages. MySQL (and other databases) will silently drop the connection. When the bot finally tries to use it, everything falls over.

The fix is simple. Spin up a background thread that pings the connection every half hour:

RAILS_DEFAULT_LOGGER.debug "Launching database connection verifier"
Thread.new do
  loop do
    sleep 1800 # Half an hour
    RAILS_DEFAULT_LOGGER.debug "Verifying database connections"
    ActiveRecord::Base.verify_active_connections!
  end
end

Drop this into your script and stale connections will be reconnected before they cause trouble.

Update: the Xeriom support bot is no longer running. It was fun, but not hugely useful in that context.