#!/bin/bash -e

# See "Running in Production" in the API Star documentation at
# <https://github.com/encode/apistar#running-in-production>

# In development, gunicorn can automatically reload code as you edit it. To
# enable this feature, export `GUNICORN_CMD_ARGS='--reload'` before running
# this script.
#
# See:
# * <http://docs.gunicorn.org/en/stable/settings.html>
# * <http://docs.gunicorn.org/en/stable/settings.html#reload>

# If the `PORT` environment variable is set, we're probably running on a
# platform like Heroku that expects the application to bind to it. Otherwise,
# default to port 5000. gunicorn will print the value on startup either way,
# allowing administrators and developers to determine the server's base URL.
#
# See:
# * <https://devcenter.heroku.com/articles/runtime-principles#web-servers>
# * <https://devcenter.heroku.com/articles/dynos#web-dynos>

PORT=${PORT:-5000}

# Run the application with gunicorn. Note that the API Star documentation
# recommends setting `--workers`. We omit this option: on our target platform,
# this is controlled automatically using the `WEB_CONCURRENCY` environment
# variable, which has a computed default based on the resources available at
# runtime. Falling back to gunicorn's default configuration is safe enough, as
# an administrator who discovers this is the wrong configuration can easily set
# `WEB_CONCURRENCY` to override it.
#
# See:
# * <https://devcenter.heroku.com/articles/python-gunicorn#basic-configuration>
# * <http://docs.gunicorn.org/en/stable/settings.html#workers>
#
# The API Star documentation also recommends the Meinheld worker type. However,
# deploying Meinheld to Heroku causes the application to fail on startup:
#
#     Error: class uri 'meinheld.gmeinheld.MeinheldWorker' invalid or not found:
#     [Traceback (most recent call last):
#       File "/app/.heroku/python/lib/python3.6/site-packages/gunicorn/util.py", line 134, in load_class
#       File "/app/.heroku/python/lib/python3.6/importlib/__init__.py", line 126, in import_module
#         mod = import_module('.'.join(components))
#         return _bootstrap._gcd_import(name[level:], package, level)
#       File "<frozen importlib._bootstrap>", line 978, in _gcd_import
#       File "<frozen importlib._bootstrap>", line 936, in _find_and_load_unlocked
#       File "<frozen importlib._bootstrap>", line 961, in _find_and_load
#       File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
#       File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked
#       File "<frozen importlib._bootstrap>", line 655, in _load_unlocked
#       File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
#       File "<frozen importlib._bootstrap_external>", line 678, in exec_module
#       File "/app/.heroku/python/lib/python3.6/site-packages/meinheld/__init__.py", line 1, in <module>
#         from meinheld.server import *
#       File "<frozen importlib._bootstrap>", line 978, in _gcd_import
#       File "<frozen importlib._bootstrap>", line 961, in _find_and_load
#     ImportError: libpython3.6m.so.1.0: cannot open shared object file: No such file or directory
#     ]
#
# The `libpython3.6m.so` library does not appear to be present. As we don't need
# to squeeze every ounce of performance out of this application, I've removed
# the Meinheld worker and opened a support ticket to get an explanation from
# Heroku.

exec gunicorn app:app \
    --bind="0.0.0.0:${PORT}"