Build less frequently

[colearendt]

close #255

• add a more robust computation of directory change
• add a check for "important_files"
• ensure that "preview-webhook" is not filtered by diffs (that feels inappropriate)

we ran into a case where a "subdirectory" of a watched directory changing (i.e. my/path, where we watch my/) would not get built. similarly, changing build infrastructure like our "version script" would not trigger new builds either.

A few open questions:

• should we remove get-diffs.py from the "important_files"
• should we consider excluding unimportant files rather than including important? i.e. should we err on the side of building too much (if a new file / directory is added) or too little (if a new global / CI affecting file is added and not added to "important_files")
• is there a better way to think about this problem?
• should we remove the "build protection" (build pass required to merge) since some builds may not run, now? Maybe a way to have an "outcome" build that succeeds only if all executed builds in the matrix pass, which we can require?
• should there be a way to ensure that "all builds get run"? Not sure what this would look like... a slash command or something?

TODO: ensure that builds will run on main when they land...

[aronatkins]

I don't completely understand why get_diffs.py is doing so many file/directory comparisons. Are we unable to rely on git diff to tell us if a given directory has changed when compared to origin/main?

git diff --quiet origin/main -- connect helper
echo $?

That returns a 0 status when nothing has changed and 1 when there are changes, and is sensitive to changes beneath connect and helper (assuming that's what we need to check).

[bschwedler]

Could we switch over to using urllib instead of requests so we can just use the standard library?

[colearendt]

Yes, that's definitely an option! Did I miss something? I thought requests was standard library at one time... but maybe that was old? Or I'm just ignorant and was using a "super standard library"

[bschwedler]

python2 had urllib, urllib2, and urllib3. requests has an a nicer interface with which to interact, but since we are using it minimally it should be easy to replace with urllib in py3.

[colearendt]

@aronatkins that's a great call. That is certainly much cleaner 😅 I was mostly cribbing from a pattern that the helm CI tools use, and a bit ignorant of niceties such as the one you mention. A few tricks / challenges that I haven't thought through yet:

• a way to reference not origin/main, but the previous parent commit (i.e. when running on main). Probably easy enough with a shell command
• where we do the check. Are we altering the matrix so that fewer jobs actually get launched as we do here, or are we checking at runtime (i.e. launch all the jobs and see whether they should exit immediately or not). I like filtering the matrix, which we could potentially do using this mechanism within the python loop
• escape hatches for "build everything" (i.e. in the daily cron job for preview, when CI-driving files change like .workflows, etc.)

I do like how elegant that is though 😄 I will revisit and see if I can simplify

[colearendt]

For the record, since this stagnated. The simple solution was to disable "rebase commits." Squash commits are safe b/c the previous commit was on main, and merge commits are safe b/c the previous commit was on main. Still much work to do teasing through these edge cases 😄

I also am hoping to take a look at the community to see if/how other teams have resolved this issue.