added observability support to processor app

apps/processor/src/telemetry/http.middleware.ts

@@ -0,0 +1,77 @@
+import { context, metrics, SpanStatusCode, trace } from "@opentelemetry/api";
+import type { MiddlewareHandler } from "hono";
+
+const tracer = trace.getTracer("processor.http");
+const meter = metrics.getMeter("processor.http");
+
+const requestCount = meter.createCounter("processor.http.server.requests", {
+    description: "Total number of processor HTTP requests",
+});
+
+const requestDuration = meter.createHistogram(
+    "processor.http.server.duration",
+    {
+        description: "Processor HTTP request duration",
+        unit: "ms",
+    },
+);
+
+const activeRequests = meter.createUpDownCounter(
+    "processor.http.server.active_requests",
+    {
+        description: "Number of in-flight processor HTTP requests",
+    },
+);
+
+export const httpTelemetryMiddleware: MiddlewareHandler = async (c, next) => {
+    const startedAt = performance.now();
+    const method = c.req.method;
+    const route = c.req.path;
+
+    const span = tracer.startSpan(`http ${method} ${route}`, {
+        attributes: {
+            "http.request.method": method,
+            "url.path": route,
+        },
+    });
+
+    activeRequests.add(1, {
+        "http.request.method": method,
+        "url.path": route,
+    });
+
+    try {
+        await context.with(trace.setSpan(context.active(), span), next);
+
+        span.setAttribute("http.response.status_code", c.res.status);
+        span.setStatus({
+            code:
+                c.res.status >= 500
+                    ? SpanStatusCode.ERROR
+                    : SpanStatusCode.OK,
+        });
+    } catch (error) {
+        span.recordException(error as Error);
+        span.setStatus({
+            code: SpanStatusCode.ERROR,
+            message: "Unhandled processor request error",
+        });
+        throw error;
+    } finally {
+        const durationMs = performance.now() - startedAt;
+        const attrs = {
+            "http.request.method": method,
+            "http.response.status_code": c.res.status,
+            "url.path": route,
+        };
+
+        requestCount.add(1, attrs);
+        requestDuration.record(durationMs, attrs);
+        activeRequests.add(-1, {
+            "http.request.method": method,
+            "url.path": route,
+        });
+
+        span.end();
+    }
+};