feat(devops): readiness probe to give build and release info

KK-1334.

The development team has decided that the readiness probe should
response with some refined server release and build information. Copied
the readiness probe implementation from Notification Service to make the
Kukkuu consistent with other apps.

Reference:
https://github.com/City-of-Helsinki/notification-service-api/blob/master/notification_service/urls.py

kukkuu/settings.py

@@ -1,5 +1,6 @@
 import os
 import subprocess
+from datetime import datetime
 
 import environ
 import sentry_sdk
@@ -88,6 +89,7 @@
     BROWSER_TEST_GROUP_NAME=(str, "Browser test"),
     BROWSER_TEST_AD_GROUP_NAME=(str, "kukkuu_browser_test"),
     KUKKUU_DEFAULT_LOGGING_LEVEL=(str, "INFO"),
+    APP_RELEASE=(str, ""),
 )
 
 if os.path.exists(env_file):
@@ -399,6 +401,11 @@
 
 HELUSERS_BACK_CHANNEL_LOGOUT_ENABLED = env("HELUSERS_BACK_CHANNEL_LOGOUT_ENABLED")
 
+# release information
+APP_RELEASE = env("APP_RELEASE")
+# get build time from a file in docker image
+APP_BUILD_TIME = datetime.fromtimestamp(os.path.getmtime(__file__))
+
 # local_settings.py can be used to override environment-specific settings
 # like database and email that differ between development and production.
 local_settings_path = os.path.join(checkout_dir(), "local_settings.py")

kukkuu/urls.py

@@ -1,6 +1,6 @@
 from django.conf import settings
 from django.conf.urls.static import static
-from django.http import HttpResponse
+from django.http import JsonResponse
 from django.urls import include, path, re_path
 from django.utils.translation import gettext_lazy as _
 from django.views.decorators.csrf import csrf_exempt
@@ -10,6 +10,7 @@
 
 from common.utils import get_api_version
 from custom_health_checks.views import HealthCheckJSONView
+from kukkuu import __version__
 from kukkuu.views import SentryGraphQLView
 from reports.api import ChildViewSet, EventGroupViewSet, EventViewSet, VenueViewSet
 
@@ -51,7 +52,14 @@
 
 
 def readiness(*args, **kwargs):
-    return HttpResponse(status=200)
+    response_json = {
+        "status": "ok",
+        "release": settings.APP_RELEASE,
+        "packageVersion": __version__,
+        "commitHash": settings.REVISION,
+        "buildTime": settings.APP_BUILD_TIME.strftime("%Y-%m-%dT%H:%M:%S.000Z"),
+    }
+    return JsonResponse(response_json, status=200)
 
 
 urlpatterns += [