Prometheus http and kernel startup/shutdown metrics

enterprise_gateway/base/handlers.py

@@ -8,6 +8,7 @@
 from typing import List
 
 import jupyter_server._version
+import prometheus_client
 from jupyter_server.base.handlers import APIHandler
 from tornado import web
 
@@ -31,6 +32,16 @@ def get(self):
         )
 
 
+class PrometheusMetricsHandler(CORSMixin, web.RequestHandler):
+    """
+    Return prometheus metrics from this enterprise gateway
+    """
+
+    def get(self):
+        self.set_header("Content-Type", prometheus_client.CONTENT_TYPE_LATEST)
+        self.write(prometheus_client.generate_latest(prometheus_client.REGISTRY))
+
+
 class NotFoundHandler(JSONErrorsMixin, web.RequestHandler):
     """
     Catches all requests and responds with 404 JSON messages.
@@ -48,4 +59,8 @@ def prepare(self):
         raise web.HTTPError(404)
 
 
-default_handlers: List[tuple] = [(r"/api", APIVersionHandler), (r"/(.*)", NotFoundHandler)]
+default_handlers: List[tuple] = [
+    (r"/api", APIVersionHandler),
+    (r"/metrics", PrometheusMetricsHandler),
+    (r"/(.*)", NotFoundHandler),
+]

enterprise_gateway/enterprisegatewayapp.py

@@ -37,6 +37,7 @@
     WebhookKernelSessionManager,
 )
 from .services.sessions.sessionmanager import SessionManager
+from .webapp import EnterpriseGatewayWebApp
 
 try:
     from jupyter_server.auth.authorizer import AllowAllAuthorizer
@@ -219,7 +220,7 @@ def init_webapp(self) -> None:
 
         handlers = self._create_request_handlers()
 
-        self.web_app = web.Application(
+        self.web_app = EnterpriseGatewayWebApp(
             handlers=handlers,
             kernel_manager=self.kernel_manager,
             session_manager=self.session_manager,

enterprise_gateway/metrics.py

@@ -0,0 +1,28 @@
+import os
+
+from prometheus_client import Histogram
+
+metrics_prefix = os.environ.get("EG_METRICS_PREFIX", "enterprise_gateway")
+
+HTTP_REQUEST_DURATION_SECONDS = Histogram(
+    'http_request_duration_seconds',
+    'Request duration for all HTTP requests',
+    ['method', 'handler', 'status_code'],
+    namespace=metrics_prefix,
+)
+
+KERNEL_START_DURATION_SECONDS = Histogram(
+    'kernel_start_duration_seconds',
+    'Kernel startup duration',
+    ['kernel_name', 'process_proxy'],
+    buckets=[0.1, 0.25, 0.5, 1, 2.5, 5.0, 10.0, 15.0, 20.0, 30.0],
+    namespace=metrics_prefix,
+)
+
+KERNEL_SHUTDOWN_DURATION_SECONDS = Histogram(
+    'kernel_shutdown_duration_seconds',
+    'Kernel startup duration for all HTTP requests',
+    ['kernel_name', 'process_proxy'],
+    buckets=[0.1, 0.25, 0.5, 1, 2.5, 5.0, 10.0, 15.0, 20.0, 30.0],
+    namespace=metrics_prefix,
+)

enterprise_gateway/services/kernels/remotemanager.py

@@ -23,6 +23,7 @@
 
 from enterprise_gateway.mixins import EnterpriseGatewayConfigMixin
 
+from ...metrics import KERNEL_SHUTDOWN_DURATION_SECONDS, KERNEL_START_DURATION_SECONDS
 from ..processproxies.processproxy import BaseProcessProxyABC, LocalProcessProxy, RemoteProcessProxy
 from ..sessions.kernelsessionmanager import KernelSessionManager
 
@@ -501,7 +502,12 @@ async def start_kernel(self, **kwargs: dict[str, Any] | None):
         """
         self._get_process_proxy()
         self._capture_user_overrides(**kwargs)
-        await super().start_kernel(**kwargs)
+        with KERNEL_START_DURATION_SECONDS.time() as timer:
+            timer.labels(
+                kernel_name=self.kernel_name,
+                process_proxy=f'{self.process_proxy.__class__.__module__}.{type(self.process_proxy).__name__}',
+            )
+            await super().start_kernel(**kwargs)
 
     def _capture_user_overrides(self, **kwargs: dict[str, Any] | None) -> None:
         """
@@ -588,6 +594,14 @@ def request_shutdown(self, restart: bool = False) -> None:
         if isinstance(self.process_proxy, RemoteProcessProxy):
             self.process_proxy.shutdown_listener()
 
+    async def shutdown_kernel(self, now: bool = False, restart: bool = False):
+        with KERNEL_SHUTDOWN_DURATION_SECONDS.time() as timer:
+            timer.labels(
+                kernel_name=self.kernel_name,
+                process_proxy=f'{self.process_proxy.__class__.__module__}.{type(self.process_proxy).__name__}',
+            )
+            await super().shutdown_kernel(now=now, restart=restart)
+
     async def restart_kernel(self, now: bool = False, **kwargs: dict[str, Any] | None) -> None:
         """
         Restarts a kernel with the arguments that were used to launch it.

enterprise_gateway/tests/test_handlers.py

@@ -557,6 +557,12 @@ def test_kernel_env_auth_token(self):
             if ws:
                 ws.close()
 
+    @gen_test
+    def test_get_metrics(self):
+        """Getting the swagger.json spec should be ok"""
+        response = yield self.http_client.fetch(self.get_url("/metrics"))
+        self.assertEqual(response.code, 200)
+
 
 class TestCustomDefaultKernel(TestHandlers):
     """Tests gateway behavior when setting a custom default kernelspec."""

enterprise_gateway/webapp.py

@@ -0,0 +1,32 @@
+
+from tornado import web
+from tornado.web import RequestHandler
+
+from enterprise_gateway.metrics import HTTP_REQUEST_DURATION_SECONDS
+
+
+class EnterpriseGatewayWebApp(web.Application):
+
+    def log_request(self, handler: RequestHandler) -> None:
+        """
+        Tornado log handler for recording RED metrics.
+
+        We record the following metrics:
+           Rate: the number of requests, per second, your services are serving.
+           Errors: the number of failed requests per second.
+           Duration: the amount of time each request takes expressed as a time interval.
+
+        We use a fully qualified name of the handler as a label,
+        rather than every url path to reduce cardinality.
+
+        This function should be either the value of or called from a function
+        that is the 'log_function' tornado setting. This makes it get called
+        at the end of every request, allowing us to record the metrics we need.
+        """
+        super().log_request(handler)
+
+        HTTP_REQUEST_DURATION_SECONDS.labels(
+            method=handler.request.method,
+            handler=f'{handler.__class__.__module__}.{type(handler).__name__}',
+            status_code=handler.get_status(),
+        ).observe(handler.request.request_time())