After searching stackoverflow for a while, I found plenty of ways to check if dockerized database service is ready before connection. So I include both of them here.
first one is written in bash script and I found it in here
if [ "$DATABASE" = "postgres" ]
then
echo "Waiting for postgres..."
while ! nc -z $SQL_HOST $SQL_PORT; do
sleep 0.1
done
echo "PostgreSQL started"
fi
python manage.py flush --no-input
python manage.py migrate
exec "$@"
The second one is written in python and I found it in here:
class Command(BaseCommand):
"""Django command that waits for database to be available"""
def handle(self, *args, **options):
"""Handle the command"""
self.stdout.write('Waiting for database...')
db_conn = None
while not db_conn:
try:
connection.ensure_connection()
db_conn = True
except OperationalError:
self.stdout.write('Database unavailable, waiting 1 second...')
time.sleep(1)
self.stdout.write(self.style.SUCCESS('Database available!'))
I use this docker command ENTRYPOINT ["/usr/src/app/entrypoint.sh"] to run the first one.
I know how to write unit tests for the second one, because it's in python. it could be something like this for example:
from unittest.mock import patch
# Use patch to to simulate db for being available or not
from django.core.management import call_command
from django.test import TestCase
class CommandTests(TestCase):
def test_wait_for_db_ready(self):
"""Test waiting for db when db is available"""
with patch('django.db.utils.ConnectionHandler.__getitem__') as gi:
gi.return_value = True
call_command('wait_for_db')
self.assertEqual(gi.call_count, 1)
But can anyone help me find a way to write tests for the first one (the bash script)?
In addition, Can anybody name what are the drawbacks and advantages of each method and also if there exists some other important considerations for writing such function? Thanks
