Pull Request: Add /metrics Endpoint with Request Tracking

__tests__/metrics.test.ts

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+import { GET } from "../app/metrics/route";
+
+describe("metrics route", () => {
+  it("returns status ok", async () => {
+    const response = await GET();
+    const text = await response.text();
+    expect(text).toEqual(expect.any(String));
+  });
+});

app/libraries/requestCounter.ts

@@ -0,0 +1,32 @@
+// lib/requestCounter.ts
+
+// Use globalThis to persist counters across module reloads
+const globalForCounters = globalThis as unknown as {
+  statusCounters: Record<string, Record<string, number>> | undefined;
+};
+
+if (!globalForCounters.statusCounters) {
+  globalForCounters.statusCounters = {};
+}
+
+const { statusCounters } = globalForCounters;
+
+export function incrementCounter(route: string, statusCode?: number) {
+  // Registers status of the response for the given route. If statusCode is undefined, it will not be counted.
+  if (statusCode !== undefined) {
+    if (!statusCounters[route]) {
+      statusCounters[route] = {};
+    }
+    const status = statusCode.toString();
+    if (statusCounters[route][status] === undefined) {
+      statusCounters[route][status] = 0;
+    }
+    statusCounters[route][status] += 1;
+  } else {
+    console.log(`Error in counting requests for the ${route}`);
+  }
+}
+
+export function getStatusCounters() {
+  return statusCounters;
+}

app/metrics/route.ts

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+import { getStatusCounters } from "../libraries/requestCounter";
+
+export async function GET() {
+  const usage = process.cpuUsage();
+  const totalSeconds = (usage.user + usage.system) / 1e6;
+  const memoria = process.memoryUsage();
+  let body = `
+# HELP up If the server is responding to HTTP requests
+# TYPE up gauge
+up 1
+# HELP process_cpu_seconds_total Total CPU time in seconds
+# TYPE process_cpu_seconds_total counter
+process_cpu_seconds_total ${totalSeconds}
+# HELP process_memoria_rss Resident Set Size: total memory allocated for the process
+# TYPE process_memoria_rss gauge
+process_memoria_rss ${memoria.rss}
+# HELP process_memoria_heapTotal Total heap size allocated.
+# TYPE process_memoria_heapTotal gauge
+process_memoria_heapTotal ${memoria.heapTotal}
+# HELP process_memoria_heapUsed Total heap size used.
+# TYPE process_memoria_heapUsed gauge
+process_memoria_heapUsed ${memoria.heapUsed}
+# HELP process_memoria_external Total external memory size.
+# TYPE process_memoria_external gauge
+process_memoria_external ${memoria.external}
+# HELP process_memoria_arrayBuffers Total array buffers size.
+# TYPE process_memoria_arrayBuffers gauge
+process_memoria_arrayBuffers ${memoria.arrayBuffers}
+`;
+
+  // Add status code metrics
+  body += "# HELP http_requests_by_status Total requests per route and status code\n";
+  body += "# TYPE http_requests_by_status counter\n";
+  const statusCounters = getStatusCounters();
+  // for loop inside for loop to iterate over all routes and status
+  Object.entries(statusCounters).forEach(([route, statuses]) => {
+    Object.entries(statuses).forEach(([status, count]) => {
+      body += `http_requests_by_status{route="${route}",status="${status}"} ${count}\n`;
+    });
+  });
+
+  return new Response(body, {
+    status: 200,
+    headers: {
+      "Content-Type": "text/plain; version=0.0.4",
+    },
+  });
+}