development-entrypoint

#! /bin/bash

# The Docker App Container's development entrypoint.
# This is a script used by the project's Docker development environment to
# setup the app containers and databases upon runnning.
set -e

: ${APP_PATH:="/app/user"}
: ${APP_TEMP_PATH:="$APP_PATH/tmp"}
: ${APP_SETUP_LOCK:="$APP_TEMP_PATH/setup.lock"}
: ${APP_SETUP_WAIT:="5"}

# 1: Define the functions lock and unlock our app containers setup processes:
function lock_setup { mkdir -p $APP_TEMP_PATH && touch $APP_SETUP_LOCK; }
function unlock_setup { rm -rf $APP_SETUP_LOCK; }
function wait_setup { echo "Waiting for app setup to finish..."; sleep $APP_SETUP_WAIT; }

# 2: 'Unlock' the setup process if the script exits prematurely:
trap unlock_setup HUP INT QUIT KILL TERM EXIT

# 3: Specify a default command, in case it wasn't issued:
if [ -z "$1" ]; then set -- rails server -p 3000 -b 0.0.0.0 "$@"; fi

# 4: Run the app setup only if the requested command requires it:
if [[ "$1" = "rails" || "$1" = "sidekiq" ]]
then
  # 5: Wait until the setup 'lock' file no longer exists:
  while [ -f $APP_SETUP_LOCK ]; do wait_setup; done

  # 6: 'Lock' the setup process, to prevent a race condition when the project's
  # app containers will try to install gems and setup the database concurrently:
  lock_setup

  # 7: Check if the database exists, or setup the database if it doesn't, as it is
  # the case when the project runs for the first time.
  #
  # We'll use a custom script `check_or_setup_db` (inside our app's `bin` folder),
  # instead of running `rake db:version  || rake db:setup`, as running that command
  # (at least on rails 4.2.4) will leave a couple of small ruby zombie processes
  # running in the container:
  bundle exec check_or_setup_db

  # 8: 'Unlock' the setup process:
  unlock_setup

  # 9: If the command to execute is 'rails server', then force it to write the pid
  # file into an private directory - suddenly killing and removing app containers
  # without this would leave a pidfile in the project's tmp dir, preventing containers
  # from starting up on further attempts:
  if [[ ("$1" = "rails" || ("$1" = "bundle" && "$2" = "exec" && "$3" = "rails")) && (("$2" = "s" || "$2" = "server") || ("$4" = "s" || "$4" = "server")) ]]; then
    rm -rf "${APP_TEMP_PATH}/pids/server.pid";
  fi
fi

# 10: Execute the given or default command:
exec "$@"