Add /metrics endpoint

Author: tankyleo

.github/workflows/build-and-deploy-rust.yml

@@ -45,6 +45,8 @@ jobs:
         run: |
           sleep 5
 
+          curl -f http://localhost:8080/metrics
+
           # Put request with store='storeId' and key=k1
           hex=0A0773746F726549641A150A026B3110FFFFFFFFFFFFFFFFFF011A046B317631
           curl -f --data-binary "$(echo "$hex" | xxd -r -p)" http://localhost:8080/vss/putObjects

rust/server/src/vss_service.rs

@@ -79,6 +79,17 @@ impl Service<Request<Incoming>> for VssService {
 		let maximum_request_body_size = self.config.maximum_request_body_size;
 
 		Box::pin(async move {
+			if path == "/metrics" {
+				let response = b"# HELP vss_service_up Is the vss service up?\n# TYPE vss_service_up gauge\nvss_service_up 1\n";
+				return Ok(Response::builder()
+					.status(StatusCode::OK)
+					.header("Content-Type", "text/plain; version=0.0.4")
+					.header(PROTOCOL_VERSION_HEADER, PROTOCOL_VERSION.as_bytes())
+					.body(Full::new(Bytes::from_static(response)))
+					// unwrap safety: body only errors when previous chained calls failed.
+					.unwrap());
+			}
+
 			let prefix_stripped_path = path.strip_prefix(BASE_PATH_PREFIX).unwrap_or_default();
 
 			match prefix_stripped_path {