App Engine: Launching a script upon update/run - ruby

Question

I'm working with App Engine and I'm thinking about using the LESS CSS extension in my next project. There's no good LESS CSS library written in Python so I went on with the original Ruby one which works great and out of the box. I'd like App Engine to execute lessc ./templates/css/style.less before running the development server and before uploading the files to the cloud. What is the best way to automate this? I'm thinking:
#run.sh:
lessc ./templates/css/style.less
.gae/dev_appserver.py --use_sqlite .
And
#deploy.sh
lessc ./templates/css/style.less
.gae/appcfg.py update .
Am I on the correct path or is there a more elegant way of doing things, perhaps at the appcfg.py level?
Thanks.

Answer 1

One option is to use the javascript version of Less and hence do the less-to-css conversion in the browser.. simply upload your less formatted file (see http://lesscss.org/ for details).
Alternately, I do the conversion (first with less, now I use sass) in a deploy script which does a number of things
checks that my source code control has no outstanding files checked out (uncommited changes)
joins and minifies my .js code (and runs jslint over it) into a single file
generates other content (including stamping the source code control version as a version number into certain key files and as a parameter on some files to avoid caching issues) so my main page pulls in scripts with URLs such as "allmysource.js?v=585".. the file might be static but the added params force cache invalidation
calls appcfg to perform the upload and checks the return code
makes some calls to the real site with wget to check the previously generated files are actually returned, by checking they're stamped with the expected version
applies another source code control tag to say that the intended version was successfully deployed
My script also accepts a "-preview" flag in which case it doesn't actually do the upload, but reports the version control comments for what's changed since the previous deployment.
me#here $ ./deploy -preview
Deployment preview...
Would deploy v596 to the production site (currently v593, previously v587)
594 Fix blah blah blah for X Y Z
595 New feature nah nah nah
596 Update help pages
This is pretty handy as a reminder of what I need to put in things like a changelog
I plan to also expand it so that I can, as part of my source code control, add any code that needs running once only when deployed (eg database schema changes) and know that it'll be automatically run when I next deploy a new version.
Essence of the script below as people asked... it doesn't show my "check code, generate, join, and minify" as that's another script... I realise that the original question was asking about that step of course :) but you can see where you'd add the call to generate CSS etc
#!/bin/sh
function abort () {
echo
echo "ERROR: $1"
echo "$2"
exit 99
}
function warn () {
echo
echo "WARNING: $1"
echo "$2"
}
# Overrides the Gentoo eselect mechanism to force the python version the GAE scripts expect
export EPYTHON=python2.5
# names of tags used to label bzr versions
CURR_DTAG=deployed
PREV_DTAG=prevDeployed
# command line options
PREVIEW=0
IGNORE_BZR=0
# These next few vars are set to values to identify my site, insert your own values here...
APPID=your_gae_appid_here
ADMIN_EMAIL=your_admin_email_address_here
SRCDIR=directory_to_deploy
CHECK_URL=url_of_page_to_retrive_that_does_upload_initialisation
for ARG; do
if [[ "$ARG" == "-preview" ]]; then
echo "Deployment preview..."
PREVIEW=1
fi
if [[ "$ARG" == "-force" ]]; then
echo "Ignoring the fact some files may not be committed to bzr..."
IGNORE_BZR=1
fi
done
echo
# check bzr for uncommited changed
BSTATUS=`bzr status`
if [[ "$BSTATUS" != "" ]]; then
if [[ "$IGNORE_BZR" == "0" ]]; then
abort "There are uncommited changes - commit/revert/ignore all files before deploying" "$BSTATUS"
else
warn "There are uncommited changes" "$BSTATUS"
fi
fi
# get version of numbers of last deployed etc
currver=`bzr log -l1 --line | sed -e 's/: .*//'`
lastver=`bzr log -rtag:${CURR_DTAG} --line | sed -e 's/: .*//'`
prevver=`bzr log -rtag:${PREV_DTAG} --line | sed -e 's/: .*//'`
lastlog=`bzr log -l 1 --line gae/changelog | sed -e 's/: .*//'`
RELEASE_NOTES=`bzr log --short --forward -r $lastver..$currver \
| perl -ne '$ver = $1 if /^ {0,4}(\d+) /; print " $ver $_" if ($ver and /^ {5,}\w/)' \
| grep -v "^ *$lastver "`
LOG_NOTES=`bzr log --short --forward -r $lastlog..$currver \
| perl -ne '$ver = $1 if /^ {0,4}(\d+) /; print " $ver $_" if ($ver and /^ {5,}\w/)' \
| grep -v "^ *$lastlog "`
# Crude but old habit - BUGBUGBUG is a marker in the code for things to be fixed before deployment
echo "Checking code for outstanding issues before deployment"
BUGSTATUS=`grep BUGBUGBUG js/*js`
if [[ "$BUGSTATUS" != "" ]]; then
if [[ "$IGNORE_BZR" == "0" ]]; then
abort "There are outstanding BUGBUGBUGs - fix them before deploying" "$BUGSTATUS"
else
warn "There are outstanding BUGBUGBUGs" "$BUGSTATUS"
fi
fi
echo
echo "Deploy v$currver to the production site (currently v$lastver, previously v$prevver)"
echo "$RELEASE_NOTES"
echo
if [[ "$currver" -gt "$lastlog" && "$lastver" -ne "$lastlog" ]]; then
echo "Changes since the changelog was last updated"
echo "$LOG_NOTES"
echo
fi
if [[ "$IGNORE_BZR" == "0" && $lastver -ge $currver ]]; then
abort "There don't appear to be any changes to deploy..."
fi
if [[ "$PREVIEW" == "1" ]]; then
exit 0
fi
$EPYTHON -c "import ssl" \
|| abort "$EPYTHON can't find ssl module for $EPYTHON - download it from pypi and install with the inbuilt setup.py"
# REMOVED - call to my script that calls jslint, generates files and compresses JS etc
# || abort "Generation of code failed"
/opt/google_appengine/appcfg.py --email=$ADMIN_EMAIL -v -A $APPID update $SRCDIR \
|| abort "Appcfg failed - upload presumably incomplete"
# move the tags to show we deployed properly
bzr tag -r $lastver --force ${PREV_DTAG}
bzr tag -r $currver --force ${CURR_DTAG}
echo
echo "Production site updated from v$lastver to v$currver (in turn from v$prevver)"
echo
echo "Now visiting $CHECK_URL to upload the source to the database"
# new version doesn't seem to always be there (may be caching by the webserver etc) to be uploaded into the database.. try again just in case
for cb in $RANDOM $RANDOM $RANDOM $RANDOM ; do
prodver=`wget $CHECK_URL?_cb=$cb -q -O - | perl -ne 'print $1 if /^\s*Rev #(\d+)\s*$/'`
if [[ "$currver" == "$prodver" ]]; then
echo "OK: New version $prodver successfully deployed"
exit 0
fi
echo "Retrying the upload of source to the database"
sleep 5
done
abort "The new source doesn't seem to be loading into the database" "Try 'wget $CHECK_URL?_cb=$RANDOM -q -O -'"
It's not particularly big or clever, but it automates the upload job