duck_punching

Dev mojo

After reading the great posts by Geoffrey “PeepCode” Grosenbach and Manfred Stienstra about using Phusion Passenger for development I had to give it a try. My doctor she’d never heard of mod_rails but gave me antibiotics for it just in case.

After little bit of setup I can say I am much happier with this dev rig than the old ‘script/server’ style. Just open a browser and the app is just waiting to serve you. Nice and agile or something.

Bugger no debugger!

One thing was missing for me though. With no –debugger switch to play with, I needed an alternative. Fortunately the brilliant ruby-debug has the solution with remote debugging. The tricky part was turning remote debugging on or off easily so we didn’t destroy our new dev mojo with onerous meddling in an environment file.

Keepin’ it real (easy)

So your working away and you run into a tough bug in some action or corner of your app. You need to break out the debugger. So the most straight forward way I have found is doing this

rake restart DEBUG=true

But how does it work. Here is a little something I prepared earlier.

In the style of passenger’s restart.txt the restart task also creates debug.txt in the tmp folder if the DEBUG switch is set to true.

Then in development.rb we look for the debug.txt file which triggers ruby-debug to be loaded. We set the ‘wait_for_connection’ option to true which gives us a chance to connect to the remote debugger when the app restarts. Finally start the debugger and clean up the debug.txt file.

From here you refresh the browser and it will it get stuck loading the page. This is because the app is waiting for you to connect to the remote debugger session. In a terminal type

rdebug -c

Once its running you can add and remove debugger statements in the code without needing to restart the debugger or the app. Now you just use the debugger as normal.

If you close the terminal or exit the debug session you can’t reconnect with it. You must do a restart with the DEBUG switch again. Once you cancel the debug session the app won’t drop into the debugger when it hits ‘debugger’ statements any more. So you can continue as normal until you need the debugger again and do a restart.

There you go, thats pretty neat and tidy and agile and whatever.

UPDATE:
I should probably mention that for ease of use and efficiency when using ruby-debug in remote mode you should probably use the ‘set autoeval’ setting. To do that create a file called .rdebugrc in your home directory and put this these lines in for good measure:

set autoeval
set autolist
set autoreload

Follow this link for more info on these settings.