Rails/Heroku CircleCI deploy script

circle.yml

checkout:
  post:
    - git submodule sync
    - git submodule update --init # use submodules
deployment:
  production:
    branch: production
    commands:
      - ./bin/heroku_deploy.sh yerdle:
          timeout: 300

heroku_deploy.sh

#!/bin/bash -e
APP_NAME=$1

# This is an adaptation of the Heroku deploy script originally written by Jonah Williams
# here: https://gist.github.com/jonah-carbonfive/5979761

# This version is designed for use with CircleCI.
# To maximize uptime, it also skips maintenance mode UNLESS one of the commits
# being deployed contains the :bomb: emoticon in the commit message.

# Unshallow the repo -- required for recent git upgrade on CircleCI
[[ ! -s "$(git rev-parse --git-dir)/shallow" ]] || git fetch --unshallow

git remote add heroku git@heroku.com:$APP_NAME.git
git fetch heroku
#MIGRATION_CHANGES=$(git diff HEAD heroku/master --name-only -- db | wc -l)
MIGRATION_CHANGES=$(git log heroku/master..HEAD | grep ':bomb:' | wc -l)
echo "$MIGRATION_CHANGES commits needing migration."

PREV_WORKERS=$(heroku ps --app $APP_NAME | grep "^worker." | wc -l | tr -d ' ')
echo "$PREV_WORKERS previous workers."
PREV_CLOCKS=$(heroku ps --app $APP_NAME | grep "^clock." | wc -l | tr -d ' ')
echo "$PREV_CLOCKS previous clocks."

# migrations require downtime so enter maintenance mode
if test $MIGRATION_CHANGES -gt 0; then
  heroku maintenance:on --app $APP_NAME

  # Make sure workers are not running during a migration
  heroku scale worker=0 clock=0 --app $APP_NAME
fi

# deploy code changes (and implicitly restart the app and any running workers)
git push heroku $CIRCLE_SHA1:refs/heads/master

# run database migrations if needed and restart background workers once finished
if test $MIGRATION_CHANGES -gt 0; then
  heroku run rake db:migrate db:seed --app $APP_NAME
  heroku scale worker=$PREV_WORKERS clock=$PREV_CLOCKS --app $APP_NAME
  heroku restart --app $APP_NAME
  heroku maintenance:off --app $APP_NAME
fi