[GitHub] [hbase] comnetwork commented on a change in pull request #3421: HBASE-26026 HBase Write may be stuck forever when using CompactingMem…

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comnetwork commented on a change in pull request #3421:
URL: https://github.com/apache/hbase/pull/3421#discussion_r657733172



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File path: hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/CompactingMemStore.java
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@@ -453,9 +453,14 @@ void flushInMemory() {
     inMemoryCompaction();
   }
 
-  private void flushInMemory(MutableSegment currActive) {
+  protected void flushInMemory(MutableSegment currActive) {
     LOG.trace("IN-MEMORY FLUSH: Pushing active segment into compaction pipeline");
-    pushActiveToPipeline(currActive);
+    // NOTE: Due to concurrent writes and because we first add cell size to currActive.getDataSize

Review comment:
       Seems that we not need synchronization here：
   1. Only one write thread can enter flushInMemory method. 
   2. An alternative fix is  we use synchronization mechanism here to prevent all writes , wait for all pending write completed(i.e. currActive.waitForUpdates is called) and if currActive is empty ,we set currActive.flushed back to false,but I am not inclined to use so heavy synchronization in write path, and I think currActive.waitForUpdates would better be put in background InMemoryCompactionRunnable.




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