Add request_duration_seconds histogram

1 files changed, 16 insertions, 7 deletions

diff --git a/src/index.ts b/src/index.ts
index a377985..ee092f2 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -34,7 +34,7 @@ collectDefaultMetrics({
     FLY_REGION: Bun.env.FLY_REGION,
   },
 });
-const counters = {
+const metrics = {
   requestsByStatus: new prom.Counter({
     name: "homestead_requests_by_status",
     help: "Number of requests by status code",
@@ -45,6 +45,11 @@ const counters = {
     help: "Number of requests by path",
     labelNames: ["path"],
   }),
+  requestDuration: new prom.Histogram({
+    name: "homestead_request_duration_seconds",
+    help: "Request duration in seconds",
+    labelNames: ["path"],
+  }),
 };
 
 let files = new Map<string, File>();
@@ -102,7 +107,7 @@ async function serveFile(
   extraHeaders: Record<string, string> = {},
 ): Promise<Response> {
   if (file && (await file.handle.exists())) {
-    counters.requestsByStatus.inc({ status_code: statusCode });
+    metrics.requestsByStatus.inc({ status_code: statusCode });
     return new Response(file.handle, {
       headers: {
         "last-modified": file.mtime.toUTCString(),
@@ -112,7 +117,7 @@ async function serveFile(
       status: statusCode,
     });
   } else {
-    counters.requestsByStatus.inc({ status_code: 404 });
+    metrics.requestsByStatus.inc({ status_code: 404 });
     // TODO return encoded
     return serveFile(files.get("/404.html"), 404);
   }
@@ -151,17 +156,18 @@ console.info(
 
 const server = Bun.serve({
   fetch: async function (request) {
+    const pathname = new URL(request.url).pathname;
+    const endTimer = metrics.requestDuration.startTimer({ path: pathname });
     try {
-      const pathname = new URL(request.url).pathname;
       const file = files.get(pathname);
-      counters.requestsByPath.inc({ path: pathname });
+      metrics.requestsByPath.inc({ path: pathname });
       if (file) {
         if (
           parseIfModifiedSinceHeader(
             request.headers.get("if-modified-since"),
           ) >= file?.mtime.getTime()
         ) {
-          counters.requestsByStatus.inc({ status_code: 304 });
+          metrics.requestsByStatus.inc({ status_code: 304 });
           return new Response("", { status: 304, headers: defaultHeaders });
         }
         const encodings = (request.headers.get("accept-encoding") || "")
@@ -192,9 +198,12 @@ const server = Bun.serve({
       }
       return serveFile(file);
     } catch (error) {
-      counters.requestsByStatus.inc({ status_code: 503 });
+      metrics.requestsByStatus.inc({ status_code: 503 });
       Sentry.captureException(error);
       return new Response("Something went wrong", { status: 503 });
+    } finally {
+      const seconds = endTimer();
+      metrics.requestDuration.observe(seconds);
     }
   },
 });