add wait_for_db command

app/app/settings.py

@@ -81,7 +81,7 @@
         'HOST': os.environ.get('DB_HOST'),
         'NAME': os.environ.get('DB_NAME'),
         'USER': os.environ.get('DB_USER'),
-        'PASSWORD': os.environ.get('DB_PASS'),
+        'PASSWORD': os.environ.get('DB_PASSWORD'),
     }
 }
 

app/core/admin.py

@@ -1,3 +1,3 @@
-from django.contrib import admin
+from django.contrib import admin # noqa
 
 # Register your models here.

app/core/management/commands/wait_for_db.py

@@ -0,0 +1,22 @@
+import time
+
+from psycopg2 import OperationalError as Psycopg2OpError
+
+from django.db.utils import OperationalError
+from django.core.management.base import BaseCommand
+
+
+class Command(BaseCommand):
+
+    def handle(self, *args, **options):
+        self.stdout.write('Waiting for db...')
+        db_up = False
+        while db_up is False:
+            try:
+                self.check(databases=['default'])
+                db_up = True
+            except (Psycopg2OpError, OperationalError):
+                self.stdout.write('db unavailable, waiting 1 second...')
+                time.sleep(1)
+
+        self.stdout.write(self.style.SUCCESS('db available!'))

app/core/models.py

@@ -1,3 +1,3 @@
-from django.db import models
+from django.db import models # noqa
 
 # Create your models here.

app/core/tests/test_commands.py

@@ -0,0 +1,31 @@
+"""
+Test custom Django management commands.
+"""
+from unittest.mock import patch
+
+from psycopg2 import OperationalError as Psycopg2OpError
+
+from django.core.management import call_command
+from django.db.utils import OperationalError
+from django.test import SimpleTestCase
+
+
+@patch('core.management.commands.wait_for_db.Command.check')
+class CommandTests(SimpleTestCase):
+
+    def test_wait_for_db_ready(self, patched_check):
+        patched_check.return_value = True
+
+        call_command('wait_for_db')
+
+        patched_check.assert_called_once_with(databases=['default'])
+
+    @patch('time.sleep')
+    def test_wait_for_db_delay(self, patched_sleep, patched_check):
+        patched_check.side_effect = [Psycopg2OpError] * 2 + \
+            [OperationalError] * 3 + [True]
+
+        call_command('wait_for_db')
+
+        self.assertEqual(patched_check.call_count, 6)
+        patched_check.assert_called_with(databases=['default'])

docker-compose.yml

@@ -16,7 +16,7 @@ services:
       - DB_HOST=db
       - DB_NAME=devdb
       - DB_USER=devuser
-      - DB_PASS=Password1
+      - DB_PASSWORD=Password1
     depends_on:
       - db