feat: Implement KEDA autoscaling configuration for probes and add metrics endpoints

Probe/API/Metrics.ts

@@ -0,0 +1,70 @@
+import Express, {
+  ExpressRequest,
+  ExpressResponse,
+  ExpressRouter,
+  NextFunction,
+} from "Common/Server/Utils/Express";
+import Response from "Common/Server/Utils/Response";
+import { PROBE_INGEST_URL } from "../Config";
+import HTTPErrorResponse from "Common/Types/API/HTTPErrorResponse";
+import HTTPMethod from "Common/Types/API/HTTPMethod";
+import HTTPResponse from "Common/Types/API/HTTPResponse";
+import URL from "Common/Types/API/URL";
+import { JSONObject } from "Common/Types/JSON";
+import API from "Common/Utils/API";
+import logger from "Common/Server/Utils/Logger";
+import ProbeAPIRequest from "../Utils/ProbeAPIRequest";
+
+const router: ExpressRouter = Express.getRouter();
+
+// Metrics endpoint for Keda autoscaling
+router.get(
+  "/queue-size",
+  async (
+    req: ExpressRequest,
+    res: ExpressResponse,
+    next: NextFunction,
+  ): Promise<void> => {
+    try {
+      // Get the pending monitor count for this specific probe from ProbeIngest API
+      const queueSizeUrl: URL = URL.fromString(
+        PROBE_INGEST_URL.toString(),
+      ).addRoute("/metrics/queue-size");
+
+      logger.debug("Fetching queue size from ProbeIngest API");
+
+      // Use probe authentication (probe key and probe ID)
+      const requestBody: JSONObject = ProbeAPIRequest.getDefaultRequestBody();
+
+      const result: HTTPResponse<JSONObject> | HTTPErrorResponse =
+        await API.fetch<JSONObject>(
+          HTTPMethod.POST,
+          queueSizeUrl,
+          requestBody,
+          {}
+        );
+
+      if (result instanceof HTTPErrorResponse) {
+        logger.error("Error fetching queue size from ProbeIngest API");
+        logger.error(result);
+        throw result; 
+      }
+
+      // Extract queueSize from the response
+      const queueSize = result.data["queueSize"] || 0;
+
+      logger.debug(`Queue size fetched: ${queueSize}`);
+
+      return Response.sendJsonObjectResponse(req, res, {
+        queueSize: queueSize,
+      });
+      
+    } catch (err) {
+      logger.error("Error in metrics queue-size endpoint");
+      logger.error(err);
+      return next(err);
+    }
+  },
+);
+
+export default router;