[GitHub] [spark] cloud-fan commented on a change in pull request #32287: [SPARK-27991][CORE] Defer the fetch request on Netty OOM

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

cloud-fan commented on a change in pull request #32287:
URL: https://github.com/apache/spark/pull/32287#discussion_r622772573



##########
File path: core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
##########
@@ -261,14 +283,38 @@ final class ShuffleBlockFetcherIterator(
             results.put(new SuccessFetchResult(BlockId(blockId), infoMap(blockId)._2,
               address, infoMap(blockId)._1, buf, remainingBlocks.isEmpty))
             logDebug("remainingBlocks: " + remainingBlocks)
+            enqueueDeferredFetchRequestIfNecessary()
           }
         }
         logTrace(s"Got remote block $blockId after ${Utils.getUsedTimeNs(startTimeNs)}")
       }
 
       override def onBlockFetchFailure(blockId: String, e: Throwable): Unit = {
         logError(s"Failed to get block(s) from ${req.address.host}:${req.address.port}", e)
-        results.put(new FailureFetchResult(BlockId(blockId), infoMap(blockId)._2, address, e))
+        val (size, mapIndex) = infoMap(blockId)
+        e match {
+          // Catching OOM and do something based on it is only a workaround for handling the
+          // Netty OOM issue, which is not the best way towards memory management. We can
+          // get rid of it when we find a way to manage Netty's memory precisely.
+
+          // Ensure the Netty memory is at least enough for serving only one block to avoid
+          // the endless retry. And since the Netty memory is shared among shuffle, rpc, etc,
+          // modules, we use "1.5" for the overhead concern.
+          case _: OutOfDirectMemoryError if PlatformDependent.maxDirectMemory() > ( 1.5 * size) =>
+            if (isNettyOOMOnShuffle.compareAndSet(false, true)) {
+              // The fetcher can fail remaining blocks in batch for the same error. So we only
+              // log the warning once to avoid flooding the logs.
+              logWarning(s"Netty OOM happens, will retry the failed blocks")
+            }
+            ShuffleBlockFetcherIterator.this.synchronized {
+              remainingBlocks -= blockId

Review comment:
       shall we add `if (!isZombie) `?




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