[GitHub] [spark] melihsozdinler commented on a diff in pull request #42071: [SPARK-44209] Expose amount of shuffle data available on the node

["melihsozdinler (via GitHub)" <gi...@apache.org>]

melihsozdinler commented on code in PR #42071:
URL: https://github.com/apache/spark/pull/42071#discussion_r1297743479


##########
common/network-shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalBlockHandler.java:
##########
@@ -101,19 +113,46 @@ public ExternalShuffleBlockResolver getBlockResolver() {
   public ExternalBlockHandler(
       OneForOneStreamManager streamManager,
       ExternalShuffleBlockResolver blockManager) {
-    this(streamManager, blockManager, new NoOpMergedShuffleFileManager(null, null));
+    this(streamManager, blockManager, new NoOpMergedShuffleFileManager(null, null), -1);
   }
 
   /** Enables mocking out the StreamManager, BlockManager, and MergeManager. */
   @VisibleForTesting
   public ExternalBlockHandler(
       OneForOneStreamManager streamManager,
       ExternalShuffleBlockResolver blockManager,
-      MergedShuffleFileManager mergeManager) {
+      MergedShuffleFileManager mergeManager,
+      int shuffleDataMetricRefreshPeriodSeconds) {
     this.metrics = new ShuffleMetrics();
     this.streamManager = streamManager;
     this.blockManager = blockManager;
     this.mergeManager = mergeManager;
+
+    if (shuffleDataMetricRefreshPeriodSeconds > 0) {
+      // We need daemon thread for shutdown hooks to be called properly
+      // This is also the reason we are not using ScheduledExecutorService
+      Runnable metricRefresherDaemon = () -> regularlyUpdateTotalShuffleDataMetric(
+          shuffleDataMetricRefreshPeriodSeconds);
+      new ThreadFactoryBuilder().setDaemon(true)
+          .setPriority(Thread.MIN_PRIORITY)
+          .setNameFormat("shuffle-data-metrics-refresher")
+          .build()
+          .newThread(metricRefresherDaemon)
+          .start();
+    }
+  }
+
+  private void regularlyUpdateTotalShuffleDataMetric(int refreshPeriod) {
+    while (true) {
+      try {
+        metrics.nodeShuffleMetrics =
+            new AtomicReference<>(blockManager.computeNodeShuffleMetrics());
+        Thread.sleep(1000L * refreshPeriod);
+      } catch (Exception e) {
+        // Catching exceptions so that subsequent executions are not suppressed
+        logger.debug("Exception occurred while calculating shuffle metrics", e);

Review Comment:
   Better to use Warn or Error level here, since it is an exception.



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