MB-49356 Part 3 (7.1.0 1745): Runtime: Don't overwrite newer cache entry

Fix requestHandlerCache.CacheLocalIndexMetadata() never to overwrite a
newer entry, which could otherwise happen if there are getIndexStatus
calls close together in time.

Change-Id: If8ed6429b32d5e10c9dc8abec3d290e1c4ff7b20

secondary/manager/request_handler.go

@@ -753,14 +753,13 @@ func (m *requestHandlerContext) getIndexStatus(creds cbauth.Creds, target *targe
 		}
 
 		// Use same un-encrypted port number as key, even if the encryption level changes in between
-		addrForKey, err := cinfo.GetServiceAddress(nid, common.INDEX_HTTP_SERVICE, false)
+		hostname, err := cinfo.GetServiceAddress(nid, common.INDEX_HTTP_SERVICE, false)
 		if err != nil {
 			logging.Debugf("RequestHandler::getIndexStatus: Error from GetServiceAddress(indexHttp, false) for node id %v. Error = %v", nid, err)
 			failedNodes = append(failedNodes, mgmtAddr)
 			continue
 		}
 
-		hostname := addrForKey
 		hostKey := Host2key(hostname) // key to caches
 		keepKeys = append(keepKeys, hostKey)
 		stale := false
@@ -1804,7 +1803,6 @@ func (m *requestHandlerContext) handleLocalIndexMetadataRequest(w http.ResponseW
 
 // getLocalIndexMetadata gets index metadata from the local metadata repo and,
 // iff it is a full set, sets its ETag info.
-
 func (m *requestHandlerContext) getLocalIndexMetadata(creds cbauth.Creds,
 	bucket string, filters map[string]bool, filterType string,
 	useETag bool) (meta *LocalIndexMetadata, timingStr string, err error) {
@@ -1877,6 +1875,7 @@ func (m *requestHandlerContext) getLocalIndexMetadata(creds cbauth.Creds,
 		topology, err = iter1.Next()
 	}
 
+	// meta.ETag and meta.ETagExpiry will stay 0 from object creation unless set here
 	if fullSet && useETag {
 		m.setETagLocalIndexMetadata(meta)
 	}

secondary/manager/request_handler_cache.go

@@ -127,15 +127,24 @@ func (this *requestHandlerCache) cacheLocalIndexMetadataBoot(hostKey string, met
 }
 
 // CacheLocalIndexMetadata adds an entry to the local metadata memory cache and stages write-through
-// to disk. hostKey is Host2key(host:httpPort).
+// to disk. hostKey is Host2key(host:httpPort). This will be skipped if a newer entry for the given
+// hostKey is already present as that would be from a newer getIndexStatus call.
 func (this *requestHandlerCache) CacheLocalIndexMetadata(hostKey string, meta *LocalIndexMetadata) {
+	isNewer := false // is the meta arg newer than current cache contents?
+
 	// Memory cache (sync)
 	this.metaMutex.Lock()
-	this.metaCache[hostKey] = meta
+	cached := this.metaCache[hostKey]
+	if cached == nil || cached.Timestamp < meta.Timestamp {
+		isNewer = true
+		this.metaCache[hostKey] = meta
+	}
 	this.metaMutex.Unlock()
 
 	// Disk cache (async)
-	this.workCh <- &workChEntry_meta{hostKey, meta}
+	if isNewer {
+		this.workCh <- &workChEntry_meta{hostKey, meta}
+	}
 }
 
 // cacheStatsBoot is called only at boot time to add an entry to the local IndexStats subset