[GitHub] [druid] yuanlihan commented on a change in pull request #11457: Improve concurrency between DruidSchema and BrokerServerView

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

yuanlihan commented on a change in pull request #11457:
URL: https://github.com/apache/druid/pull/11457#discussion_r678159621



##########
File path: sql/src/main/java/org/apache/druid/sql/calcite/schema/DruidSchema.java
##########
@@ -408,25 +479,35 @@ void addSegment(final DruidServerMetadata server, final DataSegment segment)
   @VisibleForTesting
   void removeSegment(final DataSegment segment)
   {
+    // Get lock first so that we won't wait in ConcurrentMap.compute().
     synchronized (lock) {
       log.debug("Segment[%s] is gone.", segment.getId());
 
       segmentsNeedingRefresh.remove(segment.getId());
-      mutableSegments.remove(segment.getId());
-
-      final Map<SegmentId, AvailableSegmentMetadata> dataSourceSegments =
-          segmentMetadataInfo.get(segment.getDataSource());
-      if (dataSourceSegments.remove(segment.getId()) != null) {
-        totalSegments--;
-      }
-
-      if (dataSourceSegments.isEmpty()) {
-        segmentMetadataInfo.remove(segment.getDataSource());
-        tables.remove(segment.getDataSource());
-        log.info("dataSource[%s] no longer exists, all metadata removed.", segment.getDataSource());
-      } else {
-        dataSourcesNeedingRebuild.add(segment.getDataSource());
-      }
+      unmarkSegmentAsMutable(segment.getId());
+
+      segmentMetadataInfo.compute(
+          segment.getDataSource(),
+          (dataSource, segmentsMap) -> {
+            if (segmentsMap == null) {
+              log.warn("Unknown segment[%s] was removed from the cluster. Ignoring this event.", segment.getId());
+              return null;
+            } else {
+              if (segmentsMap.remove(segment.getId()) == null) {
+                log.warn("Unknown segment[%s] was removed from the cluster. Ignoring this event.", segment.getId());
+              }
+              totalSegments--;

Review comment:
       is it better to change the count only when it's a known segment?




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