added healthcheck for redis

Author: briancaffey

backend/backend/settings/base.py

@@ -99,7 +99,6 @@
 INSTALLED_APPS = DJANGO_APPS + PROJECT_APPS + THIRD_PARTY_APPS
 
 MIDDLEWARE = [
-    'corsheaders.middleware.CorsMiddleware',
     'django.middleware.security.SecurityMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
     'social_django.middleware.SocialAuthExceptionMiddleware',
@@ -108,7 +107,6 @@
     'django.contrib.auth.middleware.AuthenticationMiddleware',
     'django.contrib.messages.middleware.MessageMiddleware',
     'django.middleware.clickjacking.XFrameOptionsMiddleware',
-    'core.middleware.SubdomainMiddleware',
 ]
 
 ROOT_URLCONF = 'backend.urls'

backend/backend/settings/development.py

@@ -21,6 +21,7 @@
 INSTALLED_APPS += DEBUG_APPS  # noqa
 
 MIDDLEWARE = [
+    'core.middleware.healthchecks.HealthCheckMiddleware',
     'debug_toolbar.middleware.DebugToolbarMiddleware',
 ] + MIDDLEWARE  # noqa
 

backend/core/middleware.py

@@ -0,0 +1,65 @@
+"""
+https://www.ianlewis.org/en/kubernetes-health-checks-django
+"""
+import logging
+import os
+
+import redis
+from django.http import HttpResponse, HttpResponseServerError
+
+logger = logging.getLogger("django")
+
+r = redis.Redis(
+    host=os.environ.get('REDIS_SERVICE_HOST')
+)
+
+
+class HealthCheckMiddleware(object):
+    def __init__(self, get_response):
+        self.get_response = get_response
+        # One-time configuration and initialization.
+
+    def __call__(self, request):
+        if request.method == "GET":
+            if request.path == "/readiness":
+                return self.readiness(request)
+            elif request.path == "/healthz":
+                return self.healthz(request)
+        return self.get_response(request)
+
+    def healthz(self, request):
+        """
+        Returns that the server is alive.
+        """
+        return HttpResponse("OK")
+
+    def readiness(self, request):
+        # Connect to each database and do a generic standard SQL query
+        # that doesn't write any data and doesn't depend on any tables
+        # being present.
+        try:
+            from django.db import connections
+            for name in connections:
+                cursor = connections[name].cursor()
+                cursor.execute("SELECT 1;")
+                row = cursor.fetchone()
+                if row is None:
+                    return HttpResponseServerError(
+                        "Postgres: invalid response")
+        except Exception as e:
+            logger.exception(e)
+            return HttpResponseServerError(
+                "Postgres: cannot connect to database.")
+
+        # Call get_stats() to connect to each memcached
+        # instance and get it's stats.
+        # This can effectively check if each is online.
+        try:
+            import redis
+            r = redis.Redis(host=os.environ.get('REDIS_SERVICE_HOST', 'redis'))
+            r.ping()
+        except Exception as e:
+            logger.exception(e)
+            return HttpResponseServerError(
+                "Redis: cannot connect to redis.")
+        return HttpResponse("OK")

backend/core/middleware/__init__.py

@@ -15,7 +15,7 @@ services:
         - HTTP_PROTOCOL=http
 
   backend:
-    image: backend:2
+    image: backend:8
     build:
       context: ../backend/
       dockerfile: scripts/dev/Dockerfile

backend/core/middleware/healthchecks.py

@@ -106,6 +106,7 @@ services:
       - GITHUB_SECRET=${GITHUB_SECRET}
       - GOOGLE_OAUTH2_KEY=${GOOGLE_OAUTH2_KEY}
       - GOOGLE_OAUTH2_SECRET=${GOOGLE_OAUTH2_SECRET}
+      - REDIS_SERVICE_HOST=redis
     depends_on:
       - postgres
 

compose/minikube.yml

@@ -310,3 +310,7 @@ https://stackoverflow.com/questions/55573426/virtualbox-is-configured-with-multi
 ```
 minikube addons enable ingress
 ```
+
+
+## Healthchecks
+

docker-compose.yml

@@ -15,8 +15,19 @@ spec:
       containers:
         - name: backend
           imagePullPolicy: IfNotPresent
-          image: backend:2
+          image: backend:8
           command: ["./manage.py", "runserver", "0.0.0.0:8000"]
+          livenessProbe:
+            httpGet:
+              path: /healthz
+              port: 8000
+          readinessProbe:
+            # an http probe
+            httpGet:
+              path: /readiness
+              port: 8000
+            initialDelaySeconds: 20
+            timeoutSeconds: 5
           ports:
           - containerPort: 8000
           env:

documentation/docs/topics/minikube/README.md

@@ -1,7 +1,7 @@
 apiVersion: v1
 kind: Service
 metadata:
-  name: redis-service
+  name: redis
 spec:
   selector:
     pod: redis