heroku deploy script

#!/bin/sh -e
APP_NAME=$1
PIPELINE_APP_NAME=$APP_NAME-slug
HEROKU_APP_REMOTE=git@heroku.com:$APP_NAME.git
HEROKU_PIPELINE_REMOTE=git@heroku.com:$PIPELINE_APP_NAME.git
WORKERS_COUNT=$(heroku ps --app $APP_NAME | grep "^worker." | wc -l | tr -d ' ')
CURRENT_BRANCH=$(git rev-parse --abbrev-ref HEAD)

LOCAL_DEPLOY_START=`date +%s`

# configure pipeline deploy https://devcenter.heroku.com/articles/labs-pipelines
if test $(heroku plugins | grep pipeline -c) -gt 0; then
  echo "Already have pipeline plugin"
else
  heroku plugins:install git://github.com/heroku/heroku-pipeline.git
fi

if test $(heroku apps | grep $PIPELINE_APP_NAME -c) -gt 0; then
  echo "Using existing pipeline $PIPELINE_APP_NAME"
  if test $(git remote -v | grep $PIPELINE_APP_NAME -c) -gt 0; then
    echo "Already have git remote"
  else
    git remote add $PIPELINE_APP_NAME $HEROKU_PIPELINE_REMOTE
    git remote add $APP_NAME $HEROKU_APP_REMOTE
  fi
  DIFF_REMOTE=$APP_NAME
else
  heroku apps:create $PIPELINE_APP_NAME --remote $PIPELINE_APP_NAME
  heroku labs:enable pipelines --app $PIPELINE_APP_NAME
  heroku pipeline:add $APP_NAME --app $PIPELINE_APP_NAME
  heroku pipeline --app $PIPELINE_APP_NAME

  git remote add $PIPELINE_APP_NAME $HEROKU_PIPELINE_REMOTE
  git remote add $APP_NAME $HEROKU_APP_REMOTE
  DIFF_REMOTE=$APP_NAME
fi

(
  PRECOMPILE_START=`date +%s`
  RAILS_ENV=production bundle exec rake assets:precompile
  git add public/assets
  git commit -m "Precompile assets"
  PRECOMPILE_END=`date +%s`
  PRECOMPILE_ELAPSED=$(( $PRECOMPILE_END - $PRECOMPILE_START ))

  echo "Precompile completed!"
  echo "  $PRECOMPILE_ELAPSED seconds"
)

# configure app and check for db changes
git fetch $DIFF_REMOTE
MIGRATION_CHANGES=$(git diff $CURRENT_BRANCH $DIFF_REMOTE/master --name-only -- db | wc -l)
echo "$MIGRATION_CHANGES db changes since last deploy."

# use pipeline to prepare a slug to deploy
git push $PIPELINE_APP_NAME $CURRENT_BRANCH:master

echo "Finished deploying to $PIPELINE_APP_NAME"

DEPLOY_START=`date +%s`

# 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 --app $APP_NAME
fi

# Run our migrations in a subprocess so that failed db migrations
# don't immediately abort our deploy script.
(
  # promote the compiled slug
  heroku pipeline:promote --app $PIPELINE_APP_NAME

  # run database migrations if needed and restart background workers once finished
  if test $MIGRATION_CHANGES -gt 0; then
    heroku run rake db:migrate --app $APP_NAME
    heroku run rake db:seed --app $APP_NAME
    heroku restart --app $APP_NAME
  fi
)

# Always scale our workers back up, regardless of whether the migration failed
if test $MIGRATION_CHANGES -gt 0; then
  heroku scale worker=$WORKERS_COUNT --app $APP_NAME
fi

heroku maintenance:off --app $APP_NAME

DEPLOY_END=`date +%s`
ELAPSED=$(( $DEPLOY_END - $DEPLOY_START ))
LOCAL_ELAPSED=$(( $DEPLOY_END - $LOCAL_DEPLOY_START ))

echo "Deploy completed!"
if test $MIGRATION_CHANGES -gt 0; then
  echo "  $ELAPSED seconds in maintenance mode."
else
  echo "  $ELAPSED seconds, without maintenance mode."
fi
echo " $LOCAL_ELAPSED seconds total."

exit 0