[GitHub] QiuMM commented on a change in pull request #6724: Fix issue that tasks failed because of no sink for identifier

[GitBox <gi...@apache.org>]

QiuMM commented on a change in pull request #6724: Fix issue that tasks failed because of no sink for identifier
URL: https://github.com/apache/incubator-druid/pull/6724#discussion_r243741074
 
 

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 File path: server/src/main/java/org/apache/druid/segment/realtime/appenderator/AppenderatorImpl.java
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 @@ -485,8 +486,12 @@ public void clear() throws InterruptedException
     final List<Pair<FireHydrant, SegmentIdentifier>> indexesToPersist = new ArrayList<>();
     int numPersistedRows = 0;
     long bytesPersisted = 0L;
-    for (SegmentIdentifier identifier : sinks.keySet()) {
-      final Sink sink = sinks.get(identifier);
+    Iterator<Map.Entry<SegmentIdentifier, Sink>> iterator = sinks.entrySet().iterator();
+
+    while (iterator.hasNext()) {
 
 Review comment:
   > So I'm wondering if it would be more correct to have this "find sinks to persist" code run in one callable together with the actual persist work in the persistExecutor as well.
   
   you are right, `persistExecutor` using a single thread, I think it will work.
   
   > There is also a code block in push that has a similar pattern that runs outside of the pushExecutor (abandonSegment uses pushBarrier()), I wonder if there are similar problems there as well:
   
   I have never observed any exceptions caused by this. And I think there is no need to worry about it because the program will wait for any outstanding pushes to finish, then abandon the segment inside the persist thread:
   ```java
   .....
   // Wait for any outstanding pushes to finish, then abandon the segment inside the persist thread.
       return Futures.transform(
           pushBarrier(),
           new Function<Object, Object>()
           {
             @Nullable
             @Override
           ......
   ```java
   

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