How do I access the current Heroku release version programmatically?

Question

Is this even possible - is there something like a RELEASE_VERSION environment variable?

Answer 1

You could do it with a .profile.d script that calls the platform API and set an environment variable:

.profile.d/release.sh

# get the unique release id and set as RELEASE_ID

# Heroku config variables that need to be set
# API_KEY: heroku api key (get from dashboard or `heroku auth:token`
# APP_NAME: set this to your app_name (this could be hardcoded in the profile.d script but
#           would make it harder to manage apps with multiple environments)

res=$(curl -s -H "Accept: application/vnd.heroku+json; version=3"\
              -H "Authorization: Bearer $API_KEY"\
              -H "Range: version ..; order=desc, max=1"\
              -X GET https://api.heroku.com/apps/$APP_NAME/releases)
release_id=$(ruby -rjson -e "j = JSON.parse('$res'); puts j[0]['id']")

export RELEASE_ID=$release_id

In a rails app, for example, ENV['RELEASE_ID'] should now be set to the most recent release id. (Python would be os.environ.get('RELEASE_ID')). The bash script uses ruby to parse the json which I think is part of the default cedar stack for any buildpack.