[GitHub] [pinot] suddendust commented on a change in pull request #7893: [7338] Allow Reloading Segments with Multiple Threads

[GitBox]

suddendust commented on a change in pull request #7893:
URL: https://github.com/apache/pinot/pull/7893#discussion_r767980451



##########
File path: 
pinot-server/src/main/java/org/apache/pinot/server/starter/helix/HelixInstanceDataManager.java
##########
@@ -212,34 +217,53 @@ public void reloadSegment(String tableNameWithType, 
String segmentName, boolean
   }
 
   @Override
-  public void reloadAllSegments(String tableNameWithType, boolean 
forceDownload) {
+  public void reloadAllSegments(String tableNameWithType, boolean 
forceDownload, int parallelism)
+      throws Exception {
     LOGGER.info("Reloading all segments in table: {}", tableNameWithType);
     TableConfig tableConfig = 
ZKMetadataProvider.getTableConfig(_propertyStore, tableNameWithType);
     Preconditions.checkNotNull(tableConfig);
 
     Schema schema = ZKMetadataProvider.getTableSchema(_propertyStore, 
tableNameWithType);
 
     List<String> failedSegments = new ArrayList<>();
-    Exception sampleException = null;
+
     List<SegmentMetadata> segmentsMetadata = 
getAllSegmentsMetadata(tableNameWithType);
+
+    int nosWorkers = Math.min(segmentsMetadata.size(), parallelism);
+
+    ExecutorService workers = Executors.newFixedThreadPool(nosWorkers);
+
+    final AtomicReference<Exception> sampleException = new AtomicReference<>();
+
+    CountDownLatch latch = new CountDownLatch(nosWorkers);
+
     for (SegmentMetadata segmentMetadata : segmentsMetadata) {
-      try {
-        reloadSegment(tableNameWithType, segmentMetadata, tableConfig, schema, 
forceDownload);
-      } catch (Exception e) {
-        String segmentName = segmentMetadata.getName();
-        LOGGER.error("Caught exception while reloading segment: {} in table: 
{}", segmentName, tableNameWithType, e);
-        failedSegments.add(segmentName);
-        sampleException = e;
-      }
+      CompletableFuture.runAsync(() -> {
+        try {
+          reloadSegment(tableNameWithType, segmentMetadata, tableConfig, 
schema, forceDownload);
+        } catch (Exception e) {
+          String segmentName = segmentMetadata.getName();
+          LOGGER.error("Caught exception while reloading segment: {} in table: 
{}", segmentName, tableNameWithType, e);
+          failedSegments.add(segmentName);
+          sampleException.set(e);
+        } finally {
+          latch.countDown();
+        }
+      }, workers);

Review comment:
       This is excellent. Thanks! Definitely need to revisit 
`CompletableFuture`'s API once.




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