kaisun2000 commented on a change in pull request #365: Fix RoutingTableProvider 
statePropagationLatency metric reporting bug
URL: https://github.com/apache/helix/pull/365#discussion_r310838708
 
 

 ##########
 File path: 
helix-core/src/main/java/org/apache/helix/spectator/RoutingTableProvider.java
 ##########
 @@ -558,23 +558,30 @@ protected void refresh(Map<String, Map<String, 
Map<String, CurrentState>>> curre
 
   private void resetRoutingTableAndNotify(long startTime, RoutingTable 
newRoutingTable) {
     _routingTableRef.set(newRoutingTable);
-    logger.info("Refresh the RoutingTable for cluster {}, takes {} ms.",
-        (_helixManager != null ? _helixManager.getClusterName() : null),
+    String clusterName = _helixManager != null ? 
_helixManager.getClusterName() : null;
+    logger.info("Refresh the RoutingTable for cluster {}, takes {} ms.", 
clusterName,
         (System.currentTimeMillis() - startTime));
-    notifyRoutingTableChange();
+
+    // TODO: move the callback user code logic to separate thread upon routing 
table statePropagation latency
+    // integration test result. If the latency is more than 2 secs, we need to 
change this part.
+    notifyRoutingTableChange(clusterName);
 
     // Update timestamp for last refresh
     if (_isPeriodicRefreshEnabled) {
       _lastRefreshTimestamp = System.currentTimeMillis();
     }
   }
 
-  private void notifyRoutingTableChange() {
-    for (Map.Entry<RoutingTableChangeListener, ListenerContext> entry : 
_routingTableChangeListenerMap
-        .entrySet()) {
-      entry.getKey().onRoutingTableChange(new 
RoutingTableSnapshot(_routingTableRef.get()),
-          entry.getValue().getContext());
+  private void notifyRoutingTableChange(String clusterName) {
+    // This call back is called in the main event queue of 
RoutingTableProvider. We add log to record time spent
+    // here. Potentially, we should call this callback in a separate thread if 
this is a bottleneck.
+    long startTime = System.currentTimeMillis();
+    for (Map.Entry<RoutingTableChangeListener, ListenerContext> entry : 
_routingTableChangeListenerMap.entrySet()) {
+      entry.getKey()
+          .onRoutingTableChange(new 
RoutingTableSnapshot(_routingTableRef.get()), entry.getValue().getContext());
     }
+    logger.info("RoutingTableProvider callback [aka not helix time] for 
cluster {}, take {} ms.", clusterName,
 
 Review comment:
   Helix Time == time spent in Helix side. Will change to this term. 
   
   No. they will not overwhelm the log. One RoutingTableProvider will be 
created by one cluster. The routingTableProvider change will not be that 
frequent, definitely should be a lot less than all the pipeline running log. So 
we should be safe here.  

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