[price-service] Update readiness probe (#893)

* [price-service] Update readiness probe

This also refactors and explains the last changes on the liveness probe.

* Update comments

* Address review comments

Author: ali-behjati

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@pythnetwork/price-service-server",
-  "version": "3.0.7",
+  "version": "3.0.8",
   "description": "Webservice for retrieving prices from the Pyth oracle.",
   "private": "true",
   "main": "index.js",

price_service/server/package.json

@@ -440,6 +440,26 @@ export class Listener implements PriceStore {
       return false;
     }
 
+    // if too many price feeds are stale it probably means that the price service
+    // is not receiving messages from Wormhole at all and is essentially dead.
+    const stalenessThreshold = 60;
+    const maxToleratedStaleFeeds = 10;
+
+    const priceIds = [...this.getPriceIds()];
+    let stalePriceCnt = 0;
+
+    for (const priceId of priceIds) {
+      const latency =
+        currentTime - this.getLatestPriceInfo(priceId)!.attestationTime;
+      if (latency > stalenessThreshold) {
+        stalePriceCnt++;
+      }
+    }
+
+    if (stalePriceCnt > maxToleratedStaleFeeds) {
+      return false;
+    }
+
     return true;
   }
 

price_service/server/src/listen.ts

@@ -514,7 +514,7 @@ export class RestAPI {
     endpoints.push("/api/stale_feeds?threshold=<staleness_threshold_seconds>");
 
     app.get("/ready", (_, res: Response) => {
-      if (this.isReady!()) {
+      if (this.isReady === undefined || this.isReady!()) {
         res.sendStatus(StatusCodes.OK);
       } else {
         res.sendStatus(StatusCodes.SERVICE_UNAVAILABLE);
@@ -523,32 +523,7 @@ export class RestAPI {
     endpoints.push("ready");
 
     app.get("/live", (_, res: Response) => {
-      const threshold = 60;
-      const stalePriceTreshold = 10;
-      const minimumNumPrices = 100;
-
-      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 (
-        priceIds.length < minimumNumPrices ||
-        stalePriceCnt > stalePriceTreshold
-      ) {
-        res.sendStatus(StatusCodes.SERVICE_UNAVAILABLE);
-      } else {
-        res.sendStatus(StatusCodes.OK);
-      }
+      res.sendStatus(StatusCodes.OK);
     });
     endpoints.push("live");