Heroku Release Phase script for managing Rails DB migrations, and playing nice with Review Apps and postdeploy scripts

00_Heroku-Release-Phase-Review-Apps-Rails_README.md

Heroku Release Phase + Review Apps + Rails

This is a simplified, but fairly thorough, set of scripts and configuration to enable Heroku Release Phase for Rails apps. Further, this particular set up plays nicely with Heroku Review Apps in that the release phase script will:

1. Fail, loudly, if the DB does not yet exist.
2. Load the DB schema if the current schema version (as determined by bin/rails db:version) is 0.
3. Run DB migrations otherwise.

For a "normal" app that usually means it will run the DB migrations. For a Review App, on the first deploy the release phase will bin/rails db:schema:load. And then the postdeploy script will seed data. During subsequent deploys to the Review App, the release phase will bin/rails db:migrate.

app.json

{
  "name": "your-app-name",
  "description": "Configuration for per-Pull-Request Reviews Apps on Heroku.",
  "scripts": {
    "postdeploy": "LOG_LEVEL=INFO bin/rake review_app:seed"
  },
  "stack": "heroku-16",
  "formation": [
    { "process": "web",    "quantity": 1 },
    { "process": "worker", "quantity": 1 }
  ],
  "addons": [
    "heroku-postgresql:hobby-dev"
  ],
  "buildpacks": [
    {
      "url": "heroku/ruby"
    }
  ],
  "env": {
    "Lots of other Env Vars...": "as you need",
    
    "HEROKU_APP_NAME": {
      "required": true
    },
    "HEROKU_PARENT_APP_NAME": {
      "required": true
    }
  }
}

bin-heroku_release.sh

#!/usr/bin/env bash
#
# Usage: bin/heroku_deploy

RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[0;33m'
NO_COLOR='\033[0m'

set -euo pipefail

schema_version=$(bin/rails db:version | { grep "^Current version: [0-9]\\+$" || true; } | tr -s ' ' | cut -d ' ' -f3)

if [ -z "$schema_version" ]; then
  printf "💀${RED}   [Release Phase]: Database schema version could not be determined. Does the database exist?${NO_COLOR}\n"
  exit 1
fi

if [ "$schema_version" -eq "0" ]; then
  printf "\n⏳${YELLOW}   [Release Phase]: Loading the database schema.${NO_COLOR}\n"
  bin/rails db:schema:load
else
  printf "\n⏳${YELLOW}   [Release Phase]: Running database migrations.${NO_COLOR}\n"
  bin/rails db:migrate
fi

printf "\n🎉${GREEN}   [Release Phase]: Database is up to date.${NO_COLOR}\n"

Procfile

web: bundle exec puma -C ./config/puma.rb
worker: DB_POOL_SIZE=${WORKER_CONCURRENCY:-20} bundle exec sidekiq -c ${WORKER_CONCURRENCY:-20} -t ${WORKER_TIMEOUT:-25} -q default,1 -q mailers,1

# === Heroku Release Phase, ignored by `heroku local`. See: https://devcenter.heroku.com/articles/release-phase
release: bin/heroku_release

review_app.rake

# frozen_string_literal: true

namespace :review_app do
  desc 'Ensure environment is one we shish to spread seed in'
  task :ensure_review_app do
    abort 'This is not a Heroku Review App' unless review_app?
  end

  desc 'Seeds a review app with a subset of realistic-looking data'
  task :seed, [] => %w[
    ensure_review_app
    environment
    db:seed
    seed:administrator
    seed:widgets
  ] do
    Rails.logger.tagged('Seed App') { |l| l.info("Finished seeding new Review App: #{ENV['HEROKU_APP_NAME']}") }
  end

  def review_app?
    !!ENV['HEROKU_PARENT_APP_NAME']
  end
end