[router] Do not classify REQUEST_ENTITY_TOO_LARGE as unhealthy (#1292)

* [router] Do not classify REQUEST_ENTITY_TOO_LARGE as unhealthy

---------

Co-authored-by: Sourav Maji <[email protected]>

Author: majisourav99

Diff for: internal/venice-test-common/src/integrationTest/java/com/linkedin/venice/router/TestRead.java

@@ -450,6 +450,8 @@ public void testRead() throws Exception {
         storeClient.batchGet(keySet).get();
         fail("Should receive exception since the batch request key count exceeds cluster-level threshold");
       } catch (Exception e) {
+        double unhealthyRequestCount = getAggregateRouterMetricValue(".total--multiget_unhealthy_request.Count");
+        Assert.assertEquals(unhealthyRequestCount, 0.0, "There should not be any unhealthy requests!");
         LOGGER.info(e);
       }
       // Bump up store-level max key count in batch-get request

Diff for: services/venice-router/src/main/java/com/linkedin/venice/router/api/RouterExceptionAndTrackingUtils.java

@@ -153,7 +153,7 @@ private static void metricTracking(
         ROUTER_STATS.getStatsByType(requestType.isPresent() ? requestType.get() : RequestType.SINGLE_GET);
     // If we don't know the actual store name, this error will only be aggregated in server level, but not
     // in store level
-    if (responseStatus.equals(BAD_REQUEST)) {
+    if (responseStatus.equals(BAD_REQUEST) || responseStatus.equals(REQUEST_ENTITY_TOO_LARGE)) {
       stats.recordBadRequest(storeName.orElse(null));
     } else if (responseStatus.equals(TOO_MANY_REQUESTS)) {
       if (storeName.isPresent()) {