From 9b521e9f36fda6914e34ce4e5e49733530871710 Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Tue, 30 Jul 2024 14:37:28 -0500
Subject: [PATCH] metricsMiddleware: add comments

---
 src/middleware/metricsMiddleware.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/middleware/metricsMiddleware.ts b/src/middleware/metricsMiddleware.ts
index d7ac43d5..f740a745 100644
--- a/src/middleware/metricsMiddleware.ts
+++ b/src/middleware/metricsMiddleware.ts
@@ -2,13 +2,19 @@ import { MiddlewareHandler } from '@hono/hono';
 
 import { httpRequestCounter, httpResponseCounter } from '@/metrics.ts';
 
+/** Prometheus metrics middleware that tracks HTTP requests by methods and responses by status code. */
 export const metricsMiddleware: MiddlewareHandler = async (c, next) => {
+  // HTTP Request.
   const { method } = c.req;
   httpRequestCounter.inc({ method });
 
+  // Wait for other handlers to run.
   await next();
 
+  // HTTP Response.
   const { status } = c.res;
+  // Get a parameterized path name like `/posts/:id` instead of `/posts/1234`.
+  // Tries to find actual route names first before falling back on potential middleware handlers like `app.use('*')`.
   const path = c.req.matchedRoutes.find((r) => r.method !== 'ALL')?.path ?? c.req.routePath;
   httpResponseCounter.inc({ status, path });
 };