[xc-server] Reliability improvements (#875)

* [xc-server] Bugfix and improvements

* Address review comments

Author: ali-behjati

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@pythnetwork/price-service-server",
-  "version": "3.0.5",
+  "version": "3.0.6",
   "description": "Webservice for retrieving prices from the Pyth oracle.",
   "private": "true",
   "main": "index.js",

price_service/server/package.json

@@ -191,12 +191,12 @@ export class Listener implements PriceStore {
     this.spyServiceHost = config.spyServiceHost;
     this.loadFilters(config.filtersRaw);
     // Don't store any prices received from wormhole that are over 5 minutes old.
-    this.ignorePricesOlderThanSecs = 5 * 60;
+    this.ignorePricesOlderThanSecs = 60;
     this.readinessConfig = config.readiness;
     this.updateCallbacks = [];
     this.observedVaas = new LRUCache({
-      max: 100000, // At most 100000 items
-      ttl: 6 * 60 * 1000, // 6 minutes which is longer than ignorePricesOlderThanSecs
+      max: 10000, // At most 10000 items
+      ttl: 60 * 1000, // 1 minutes which is equal to ignorePricesOlderThanSecs
     });
     this.vaasCache = new VaaCache(
       config.cacheTtl,

price_service/server/src/listen.ts

@@ -523,7 +523,28 @@ export class RestAPI {
     endpoints.push("ready");
 
     app.get("/live", (_, res: Response) => {
-      res.sendStatus(StatusCodes.OK);
+      const threshold = 60;
+      const stalePriceTreshold = 10;
+
+      const currentTime: TimestampInSec = Math.floor(Date.now() / 1000);
+
+      const priceIds = [...this.priceFeedVaaInfo.getPriceIds()];
+      let stalePriceCnt = 0;
+
+      for (const priceId of priceIds) {
+        const latency =
+          currentTime -
+          this.priceFeedVaaInfo.getLatestPriceInfo(priceId)!.attestationTime;
+        if (latency > threshold) {
+          stalePriceCnt++;
+        }
+      }
+
+      if (stalePriceCnt > stalePriceTreshold) {
+        res.sendStatus(StatusCodes.SERVICE_UNAVAILABLE);
+      } else {
+        res.sendStatus(StatusCodes.OK);
+      }
     });
     endpoints.push("live");