I made a change to the official mongodb charm.
Before the change, the install step, when deploying the charm took 5 minutes.
2014-11-17 20:54:13 Installing mongodb
2014-11-17 21:04:12 Entering config_changed
After the change, the install step, when deploying took a tiny bit over 2 minutes.
2014-11-19 19:14:55 Installing mongodb
2014-11-19 19:16:06 Entering config_changed
Before: Fetched 46.2 MB
After: Fetched 14.6 MB
Why the huge change? The charm was previously running ‘apt-get install mongodb’ which Recommends the mongodb-dev package which Depends on development packages, ultimately pulling in a c++ compiler and boost dev libraries and header files.
I am happy to download 1/4 of what I previously was required to download for the same functionality.
When writing charms for juju, or automating your deploys using any other tool, remember consider what the system is really doing with the commands you give it.
I highly recommend always running apt-get install with the –no-install-recommends option when you are in a server environment. You’ll waste less time.
A note on the time comparison: At first I hesitated to write this, because the hardware on which I tested this is doing other things. I then realized that this is exactly what all hardware in the cloud is doing all the time. This isn’t a benchmark. This isn’t a timing test. This is an example of making a single case of something slow, a bit faster.