Configuration added to wait for database.

.github/workflows/checks.yml

@@ -16,6 +16,6 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v2
       - name: Test
-        run: docker-compose run --rm app sh -c "python manage.py test"
+        run: docker-compose run --rm app sh -c "python manage.py wait_for_db && python manage.py test"
       - name: Lint
         run: docker-compose run --rm app sh -c "flake8"

Dockerfile

@@ -12,11 +12,15 @@ EXPOSE 8000
 ARG DEV=false
 RUN python -m venv /py && \
     /py/bin/pip install --upgrade pip && \
+    apk add --update --no-cache postgresql-client && \
+    apk add --update --no-cache --virtual .tmp-build-deps \
+        build-base postgresql-dev musl-dev && \
     /py/bin/pip install -r /tmp/requirements.txt && \
     if [ $DEV = "true" ]; \
         then /py/bin/pip install -r /tmp/requirements.dev.txt ; \
     fi && \
     rm -rf /tmp && \
+    apk del .tmp-build-deps && \
     adduser \
         --disabled-password \
         --no-create-home \

app/app/calc.py

@@ -0,0 +1,13 @@
+"""
+Calculator functions
+"""
+
+
+def add(x, y):
+    """Add x and y and return result."""
+    return x + y
+
+
+def subtract(x, y):
+    """ Subtract x from y and return result."""
+    return y - x

app/app/settings.py

@@ -10,6 +10,7 @@
 https://docs.djangoproject.com/en/3.2/ref/settings/
 """
 
+import os
 from pathlib import Path
 
 # Build paths inside the project like this: BASE_DIR / 'subdir'.
@@ -37,6 +38,7 @@
     'django.contrib.sessions',
     'django.contrib.messages',
     'django.contrib.staticfiles',
+    'core',
 ]
 
 MIDDLEWARE = [
@@ -75,8 +77,11 @@
 
 DATABASES = {
     'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': BASE_DIR / 'db.sqlite3',
+        'ENGINE': 'django.db.backends.postgresql',
+        'HOST': os.environ.get('DB_HOST'),
+        'NAME': os.environ.get('DB_NAME'),
+        'USER': os.environ.get('DB_USER'),
+        'PASSWORD': os.environ.get('DB_PASS'),
     }
 }
 

app/app/test.py

@@ -0,0 +1,22 @@
+"""
+Sample tests
+"""
+from django.test import SimpleTestCase
+
+from app import calc
+
+
+class CalcTests(SimpleTestCase):
+    """Test the calc module"""
+
+    def test_add_numbers(self):
+        """Test adding numbers together."""
+        res = calc.add(5, 6)
+
+        self.assertEqual(res, 11)
+
+    def test_subtract_numbers(self):
+        """Test subtracting numbers."""
+        res = calc.subtract(10, 15)
+
+        self.assertEqual(res, 5)

app/core/admin.py

@@ -0,0 +1,3 @@
+from django.contrib import admin # noqa
+
+# Register your models here.

app/core/apps.py

@@ -0,0 +1,6 @@
+from django.apps import AppConfig
+
+
+class CoreConfig(AppConfig):
+    default_auto_field = 'django.db.models.BigAutoField'
+    name = 'core'

app/core/management/commands/wait_for_db.py

@@ -0,0 +1,24 @@
+"""
+Django command to wait for the database to be available.
+"""
+
+import time
+from psycopg2 import OperationalError as Psycopg2OpError
+
+from django.db.utils import OperationalError
+from django.core.management.base import BaseCommand
+
+
+class Command(BaseCommand):
+    """Base command to wait for the database."""
+    def handle(self, *args, **options):
+        self.stdout.write('Waiting for database...')
+        db_up = False
+        while db_up is False:
+            try:
+                self.check(databases=['default'])
+                db_up = True
+            except (Psycopg2OpError, OperationalError):
+                self.stdout.write('Database unavailable, waiting 1 second...')
+                time.sleep(1)
+        self.stdout.write(self.style.SUCCESS('Database available!'))

app/core/models.py

@@ -0,0 +1,3 @@
+from django.db import models # noqa
+
+# Create your models here.

app/core/tests/test_commands.py

@@ -0,0 +1,46 @@
+"""
+Test Django management commands.
+"""
+
+from unittest.mock import patch
+
+from psycopg2 import OperationalError as Psycopg2Error
+
+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):
+    """Test commands."""
+
+    def test_wait_for_db_ready(self, patched_check):
+        """Test waiting for database if database ready."""
+        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):
+        """Test waiting for database when getting OperationalError."""
+
+        """
+        This is the way we throw exceptions instead of returning a
+        simple value (True of False). Recall that patch is simulating the
+        behaviour of the connection to the database.
+        """
+        patched_check.side_effect = [Psycopg2Error] * 2 + \
+            [OperationalError] * 3 + [True]
+
+        call_command('wait_for_db')
+
+        """
+        We expect to call the method 6 times until we get a True.
+        That's defined in patched_check list.
+        """
+        self.assertEqual(patched_check.call_count, 6)
+
+        patched_check.assert_called_with(databases=['default'])

docker-compose.yml

@@ -11,5 +11,27 @@ services:
     volumes:
       - ./app:/app
     command: >
-      sh -c "python manage.py runserver 0.0.0.0:8000"
+      sh -c "python manage.py wait_for_db &&
+             python manage.py migrate &&
+             python manage.py runserver 0.0.0.0:8000"
+    environment:
+      - DB_HOST=db
+      - DB_NAME=devdb
+      - DB_USER=devuser
+      - DB_PASS=changeme
+    depends_on:
+      - db
 
+  db:
+    image: postgres:13-alpine
+    volumes:
+      - dev-db-data:/var/lib/postgresql/data
+    environment:
+      - POSTGRES_DB=devdb
+      - POSTGRES_USER=devuser
+      - POSTGRES_PASSWORD=changeme
+
+
+
+volumes:
+  dev-db-data:

requirements.txt

@@ -1,2 +1,3 @@
 Django>=3.2.4,<3.3
 djangorestframework>=3.12.4,<3.13
+psycopg2>=2.8.6,<2.9