Monitoring: tag HTTP response rate histogram by route rather than request url

Author: TheArcaneBrony

src/util/monitoring/Monitoring.ts

@@ -16,9 +16,10 @@
 	along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
-import * as client from "prom-client";
-import { Router } from "express";
 import http, { IncomingMessage, ServerResponse } from "node:http";
+import * as client from "prom-client";
+import { Application, Router } from "express";
+import { sleep } from "@spacebar/util";
 
 export class Monitoring {
     static isInitialised = false;
@@ -29,8 +30,38 @@ export class Monitoring {
         Monitoring.isInitialised = true;
     }
 
-    public static attach(router: Router) {
-        router.get("/metrics", async (req, res) => {
+    public static attach(app: Application) {
+        const a = app;
+        const http_request_total = new client.Counter({
+            name: "node_http_request_total",
+            help: "The total number of HTTP requests received",
+            labelNames: ["path", "method", "status_code"],
+        });
+        client.register.registerMetric(http_request_total);
+
+        const http_response_rate_histogram = new client.Histogram({
+            name: "node_http_duration",
+            labelNames: ["path", "method", "status_code"],
+            help: "The duration of HTTP requests in seconds",
+            buckets: [0.0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 10],
+        });
+        client.register.registerMetric(http_response_rate_histogram);
+
+        app.use((req, res, next) => {
+            const endTimer = http_response_rate_histogram.startTimer();
+            res.on("finish", () => {
+                const r = req;
+                const path = (res.locals.lambertRouteBase ?? req.baseUrl ?? "") + req.route?.path;
+                if (!req.route?.path) {
+                    console.log(req);
+                }
+                endTimer({ method: req.method, path, status_code: res.statusCode });
+                http_request_total.inc({ method: req.method, path, status_code: res.statusCode });
+            });
+            next();
+        });
+
+        app.get("/metrics", async (req, res) => {
             res.setHeader("Content-Type", client.register.contentType);
             const metrics = await client.register.metrics();
             res.send(metrics);

src/util/util/lambert-server/Server.ts

@@ -54,7 +54,15 @@ export class Server {
             if (router.default) router = router.default;
             if (!router || router?.prototype?.constructor?.name !== "router") throw `File doesn't export any default router`;
 
-            this.app.use(path, <Router>router);
+            this.app.use(
+                path,
+                // TODO: I wish this middleware wasn't nessecary to preserve base path param names for monitoring...
+                (_, res, next) => {
+                    res.locals.lambertRouteBase = path;
+                    next();
+                },
+                <Router>router,
+            );
 
             if (this.options.serverInitLogging && process.env.LOG_ROUTES !== "false") console.log(`[Server] Route ${path} registered`);