zhangmeng916 commented on a change in pull request #1124:
URL: https://github.com/apache/helix/pull/1124#discussion_r456054406
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File path:
helix-core/src/main/java/org/apache/helix/controller/stages/CurrentStateComputationStage.java
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@@ -77,15 +84,19 @@ public void process(ClusterEvent event) throws Exception {
String instanceName = instance.getInstanceName();
String instanceSessionId = instance.getEphemeralOwner();
- // update pending messages
- Map<String, Message> messages = cache.getMessages(instanceName);
- Map<String, Message> relayMessages =
cache.getRelayMessages(instanceName);
- updatePendingMessages(instance, messages.values(), currentStateOutput,
relayMessages.values(), resourceMap);
-
// update current states.
Map<String, CurrentState> currentStateMap =
cache.getCurrentState(instanceName,
instanceSessionId);
updateCurrentStates(instance, currentStateMap.values(),
currentStateOutput, resourceMap);
+
+ Map<String, Map<String, Message>> existingStaleMessages =
cache.getStaleMessages();
+ currentStateOutput.setStaleMessageMap(existingStaleMessages);
+ // update pending messages
+ Map<String, Message> messages = cache.getMessages(instanceName);
+ Map<String, Message> relayMessages =
cache.getRelayMessages(instanceName);
+ updatePendingMessages(instance, messages.values(), currentStateOutput,
+ relayMessages.values(), resourceMap, existingStaleMessages);
+ cache.setStaleMessages(currentStateOutput.getStaleMessageMap());
Review comment:
The purpose of the cache is not for performance, but to keep all the
historical stale messages. For example, assume a partition goes through
M->S->M->S, and the first M->S message is not deleted even during the second
M->S transition, if we only look at pending messages only, the first M->S
message would be considered as non stale message, which causes confusion. With
the cache, the stale messages would not be checked again.
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