add health endpoint to metrics asgi app

logprep/metrics/exporter.py

@@ -9,23 +9,39 @@
 from logprep.util import http
 from logprep.util.configuration import MetricsConfig
 
+prometheus_app = make_asgi_app(REGISTRY)
+
+logger = getLogger("Exporter")
+
+
+async def asgi_app(scope, receive, send):
+    """asgi app with health check and metrics handling"""
+    if scope["type"] == "http" and scope["path"] == "/health":
+        await send(
+            {
+                "type": "http.response.start",
+                "status": 200,
+            }
+        )
+        await send({"type": "http.response.body", "body": b"OK"})
+    else:
+        await prometheus_app(scope, receive, send)
+
 
 class PrometheusExporter:
     """Used to control the prometheus exporter and to manage the metrics"""
 
     def __init__(self, configuration: MetricsConfig):
         self.is_running = False
-        logger_name = "Exporter"
-        self._logger = getLogger(logger_name)
-        self._logger.debug("Initializing Prometheus Exporter")
+        logger.debug("Initializing Prometheus Exporter")
         self.configuration = configuration
         self._port = configuration.port
-        self._app = make_asgi_app(REGISTRY)
+        self._app = asgi_app
         self._server = http.ThreadingHTTPServer(
             configuration.uvicorn_config | {"port": self._port, "host": "0.0.0.0"},
             self._app,
             daemon=True,
-            logger_name=logger_name,
+            logger_name="Exporter",
         )
 
     def _prepare_multiprocessing(self):
@@ -45,7 +61,7 @@ def cleanup_prometheus_multiprocess_dir(self):
                 os.remove(os.path.join(root, file))
             for directory in dirs:
                 shutil.rmtree(os.path.join(root, directory), ignore_errors=True)
-        self._logger.info("Cleaned up %s", multiprocess_dir)
+        logger.info("Cleaned up %s", multiprocess_dir)
 
     def mark_process_dead(self, pid):
         """
@@ -63,5 +79,5 @@ def run(self):
         """Starts the default prometheus http endpoint"""
         self._prepare_multiprocessing()
         self._server.start()
-        self._logger.info("Prometheus Exporter started on port %s", self._port)
+        logger.info("Prometheus Exporter started on port %s", self._port)
         self.is_running = True

tests/unit/metrics/test_exporter.py

@@ -2,15 +2,24 @@
 # pylint: disable=protected-access
 # pylint: disable=attribute-defined-outside-init
 # pylint: disable=line-too-long
+import asyncio
 import os.path
-from logging.config import dictConfig
 from unittest import mock
 
+import pytest
+import requests
 from prometheus_client import REGISTRY
 
 from logprep.metrics.exporter import PrometheusExporter
+from logprep.util import configuration, http
 from logprep.util.configuration import MetricsConfig
-from logprep.util.defaults import DEFAULT_LOG_CONFIG
+
+
+@pytest.fixture
+def loop():
+    loop = asyncio.new_event_loop()
+    yield loop
+    loop.close()
 
 
 @mock.patch(
@@ -79,3 +88,16 @@ def test_mark_process_dead_calls_multiprocess_mark_dead(self, mock_multiprocess)
     def test_exporter_spawns_server_on_all_interfaces(self):
         exporter = PrometheusExporter(self.metrics_config)
         assert exporter._server.server.config.host == "0.0.0.0"
+
+    def test_health_endpoint_returns_200(self):
+        exporter = PrometheusExporter(self.metrics_config)
+        exporter._server = http.ThreadingHTTPServer(
+            self.metrics_config.uvicorn_config | {"port": "8000", "host": "0.0.0.0"},
+            exporter._app,
+            daemon=False,
+            logger_name="Exporter",
+        )
+        exporter.run()
+        resp = requests.get("http://localhost:8000/health")
+        assert resp.status_code == 200
+        exporter._server.shut_down()