Improve build slowness

[mbland]

Per yesterday's Documentation Working Group discussion, build times for the Hub appear to be creeping up. This makes Javascript development especially painful.

Using the ruby-prof gem via the following command reaffirmed common knowledge that Liquid accounts for most of the time:

$ bundle exec ruby-prof --printer=call_stack --file=stack.out /usr/local/var/rbenv/versions/2.2.0/bin/jekyll -- build

Cloning the Jekyll repo and building a 3.0.0.pre.beta1 gem from the master branch didn't appear to impact the time very much.

Some relevant links:

• jekyll serve is pretty slow recently jekyll/jekyll#3009
• Incremental regeneration jekyll/jekyll#3116
• 3.0 RELEASE GAMEPLAN jekyll/jekyll#3324
• Some input on 3.0.0 jekyll/jekyll#3350
• https://tuananh.org/2014/07/26/speed-up-jekyll-site-generation-with-rsync/

Possible approaches:

• Reduce the number of Liquid expressions in Hub templates
• Reduce number of Hub layouts
• Optimize Jekyll
• Optimize Liquid
• Come up with an alternate Javascript development scheme

cc: @shawnbot @msecret @afeld @gboone

[dhcole]

In case this is helpful: jekyll/jekyll#1140 (comment)

[afeld]

Made an issue for jekyll_pages_api as well: 18F/jekyll_pages_api#20

[envygeeks]

Are these raw benches or raw + parboiled benches? We have incremental regeneration so I would be interested in seeing what it's like after the raw build (on 3.0) but if that does not speed things up then we do have a problem that needs to be solved.

[mbland]

I'm sure I didn't do a very thorough job with the benchmarks, as I'm not much of a Rubyist. If you've a preferred methodology documented somewhere, I can study up and take another shot. Anecdotally, it seemed like rebuilds were still on the order of 5-6s on my Yosemite machine, even with 3.0.0.pre.beta1; @shawnbot, running Mavericks, was getting O(30s) using 2.5.3.

FWIW, we're also considering changing the architecture of the application in a way that may mitigate the problem (though that's not the only reason for the architectural change).

[ac70]

this may or may not help, but I cloned my jekyll repo and started setting it up to use with Grunt. I didn't quite get there, but when I went back to trying to serve with Jekyll it was taking 1m+ for every save. Maybe the added files caused this?

I switched back to the previous version and Jekyll serve is working fine again.