From a4a275d0fdfef229586985084dc482b3d84ce95f Mon Sep 17 00:00:00 2001
From: Luis Alvergue <luis@compiler.la>
Date: Mon, 9 Dec 2024 22:58:04 +0000
Subject: [PATCH] feat: implement /healthcheck endpoint

implements the healthcheck as a middleware before the HOST_HEADER verification (in django.middleware.common.CommonMiddleware), so healthcheck requests always pass

based on https://stackoverflow.com/a/64623669
---
 pems/core/__init__.py                         |  0
 pems/core/middleware.py                       | 19 +++++++++++++++++++
 pems/settings.py                              |  1 +
 tests/pytest/core/__init__.py                 |  0
 .../core/test_middleware_healthcheck.py       |  6 ++++++
 5 files changed, 26 insertions(+)
 create mode 100644 pems/core/__init__.py
 create mode 100644 pems/core/middleware.py
 create mode 100644 tests/pytest/core/__init__.py
 create mode 100644 tests/pytest/core/test_middleware_healthcheck.py

diff --git a/pems/core/__init__.py b/pems/core/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/pems/core/middleware.py b/pems/core/middleware.py
new file mode 100644
index 0000000..284c2ee
--- /dev/null
+++ b/pems/core/middleware.py
@@ -0,0 +1,19 @@
+"""
+The core application: middleware definitions for request/response cycle.
+"""
+
+from django.http import HttpResponse
+
+HEALTHCHECK_PATH = "/healthcheck"
+
+
+class Healthcheck:
+    """Middleware intercepts and accepts /healthcheck requests."""
+
+    def __init__(self, get_response):
+        self.get_response = get_response
+
+    def __call__(self, request):
+        if request.path == HEALTHCHECK_PATH:
+            return HttpResponse("Healthy", content_type="text/plain")
+        return self.get_response(request)
diff --git a/pems/settings.py b/pems/settings.py
index d034edf..d834a1f 100644
--- a/pems/settings.py
+++ b/pems/settings.py
@@ -36,6 +36,7 @@ def _filter_empty(ls):
 MIDDLEWARE = [
     "django.middleware.security.SecurityMiddleware",
     "django.contrib.sessions.middleware.SessionMiddleware",
+    "pems.core.middleware.Healthcheck",
     "django.middleware.common.CommonMiddleware",
     "django.middleware.csrf.CsrfViewMiddleware",
     "django.contrib.auth.middleware.AuthenticationMiddleware",
diff --git a/tests/pytest/core/__init__.py b/tests/pytest/core/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/pytest/core/test_middleware_healthcheck.py b/tests/pytest/core/test_middleware_healthcheck.py
new file mode 100644
index 0000000..1519fa0
--- /dev/null
+++ b/tests/pytest/core/test_middleware_healthcheck.py
@@ -0,0 +1,6 @@
+from pems.core.middleware import HEALTHCHECK_PATH
+
+
+def test_healthcheck(client):
+    response = client.get(HEALTHCHECK_PATH)
+    assert response.status_code == 200