[GitHub] [spark] attilapiros commented on a change in pull request #29014: [SPARK-32199][SPARK-32198] Reduce job failures during decommissioning

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

attilapiros commented on a change in pull request #29014:
URL: https://github.com/apache/spark/pull/29014#discussion_r457378657



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File path: core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala
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@@ -1767,10 +1767,18 @@ private[spark] class DAGScheduler(
 
           // TODO: mark the executor as failed only if there were lots of fetch failures on it
           if (bmAddress != null) {
-            val hostToUnregisterOutputs = if (env.blockManager.externalShuffleServiceEnabled &&
-              unRegisterOutputOnHostOnFetchFailure) {
-              // We had a fetch failure with the external shuffle service, so we
-              // assume all shuffle data on the node is bad.
+            val externalShuffleServiceEnabled = env.blockManager.externalShuffleServiceEnabled
+            val isHostDecommissioned = taskScheduler
+              .getExecutorDecommissionInfo(bmAddress.executorId)
+              .exists(_.isHostDecommissioned)
+            // Host shuffle data is considered lost if:
+            // - If we know that the host was decommissioned
+            // - Or when `unRegisterOutputOnHostOnFetchFailure` is enabled and we had
+            //   a fetch failure with the external shuffle service, so we assume all
+            //   shuffle data on the node is bad.
+            val hostLost = isHostDecommissioned || (externalShuffleServiceEnabled &&

Review comment:
       I have two issues:
   
   1) As the `unRegisterOutputOnHostOnFetchFailure` is a feature flag for the unregistering with the following description:
   
   https://github.com/apache/spark/blob/a4ca355af8556e8c5948e492ef70ef0b48416dc4/core/src/main/scala/org/apache/spark/internal/config/package.scala#L794-L801
   
   But with your change when the host is decommissioned the feature flag is not considered at all and the unregistering will happen. I see the benefit to do the unregistering but if you leave this condition as it is now then please update the feature flag description too.
   
   2) Can we find a different name from `hostLost`? As the host can be lost even when  `unRegisterOutputOnHostOnFetchFailure` is false. Or just inline this val as the comment above must be sufficient.




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