fix leaky segment reference on segment drop

processing/src/test/java/org/apache/druid/segment/TestSegmentUtils.java

@@ -126,6 +126,12 @@ public List<OrderBy> getOrdering()
     {
       return Cursors.ascendingTimeOrder();
     }
+
+    @Override
+    public int getNumRows()
+    {
+      return 1234;
+    }
   };
 
   public static class SegmentForTesting extends QueryableIndexSegment
@@ -178,6 +184,8 @@ public <T> T as(@Nonnull Class<T> clazz)
         return (T) INDEX;
       } else if (clazz.equals(CursorFactory.class)) {
         return (T) new QueryableIndexCursorFactory(INDEX);
+      } else if (clazz.equals(PhysicalSegmentInspector.class)) {
+        return (T) new QueryableIndexPhysicalSegmentInspector(INDEX);
       }
       return null;
     }

server/src/main/java/org/apache/druid/segment/loading/SegmentLocalCacheManager.java

@@ -648,6 +648,25 @@ boolean isSegmentCached(final DataSegment segment)
     return false;
   }
 
+  /**
+   * Testing use only please, any callers that want to do stuff with segments should use
+   * {@link #acquireCachedSegment(DataSegment)} or {@link #acquireSegment(DataSegment)} instead. Does not hold locks
+   * and so is not really safe to use while the cache manager is active
+   */
+  @VisibleForTesting
+  @Nullable
+  public ReferenceCountedSegmentProvider getSegmentReferenceProvider(DataSegment segment)
+  {
+    final SegmentCacheEntry cacheEntry = new SegmentCacheEntry(segment);
+    for (StorageLocation location : locations) {
+      final SegmentCacheEntry entry = location.getCacheEntry(cacheEntry.id);
+      if (entry != null) {
+        return entry.referenceProvider;
+      }
+    }
+    return null;
+  }
+
   /**
    * Returns the effective segment info directory based on the configuration settings.
    * The directory is selected based on the following configurations injected into this class:

server/src/main/java/org/apache/druid/server/SegmentManager.java

@@ -380,11 +380,11 @@ public void dropSegment(final DataSegment dataSegment)
               try (final Closer closer = Closer.create()) {
                 final Optional<Segment> oldSegment = cacheManager.acquireCachedSegment(oldSegmentRef);
                 long numberOfRows = oldSegment.map(segment -> {
+                  closer.register(segment);
                   final PhysicalSegmentInspector countInspector = segment.as(PhysicalSegmentInspector.class);
                   if (countInspector != null) {
                     return countInspector.getNumRows();
                   }
-                  CloseableUtils.closeAndWrapExceptions(segment);
                   return 0;
                 }).orElse(0);
 

server/src/test/java/org/apache/druid/server/SegmentManagerTest.java

@@ -35,6 +35,7 @@
 import org.apache.druid.query.expression.TestExprMacroTable;
 import org.apache.druid.segment.IndexIO;
 import org.apache.druid.segment.IndexSpec;
+import org.apache.druid.segment.ReferenceCountedSegmentProvider;
 import org.apache.druid.segment.SegmentLazyLoadFailCallback;
 import org.apache.druid.segment.SegmentMapFunction;
 import org.apache.druid.segment.TestHelper;
@@ -45,7 +46,6 @@
 import org.apache.druid.segment.loading.LeastBytesUsedStorageLocationSelectorStrategy;
 import org.apache.druid.segment.loading.LocalDataSegmentPuller;
 import org.apache.druid.segment.loading.LocalLoadSpec;
-import org.apache.druid.segment.loading.SegmentCacheManager;
 import org.apache.druid.segment.loading.SegmentLoaderConfig;
 import org.apache.druid.segment.loading.SegmentLoadingException;
 import org.apache.druid.segment.loading.SegmentLocalCacheManager;
@@ -90,7 +90,9 @@ public class SegmentManagerTest extends InitializedNullHandlingTest
   );
 
   private ExecutorService executor;
+  private SegmentLocalCacheManager cacheManager;
   private SegmentManager segmentManager;
+  private SegmentLocalCacheManager virtualCacheManager;
   private SegmentManager virtualSegmentManager;
 
   @Rule
@@ -160,7 +162,7 @@ public boolean isVirtualStorage()
     );
 
     final List<StorageLocation> storageLocations = loaderConfig.toStorageLocations();
-    final SegmentLocalCacheManager cacheManager = new SegmentLocalCacheManager(
+    cacheManager = new SegmentLocalCacheManager(
         storageLocations,
         loaderConfig,
         new LeastBytesUsedStorageLocationSelectorStrategy(storageLocations),
@@ -170,7 +172,7 @@ public boolean isVirtualStorage()
     segmentManager = new SegmentManager(cacheManager);
 
     final List<StorageLocation> virtualStorageLocations = virtualLoaderConfig.toStorageLocations();
-    final SegmentCacheManager virtualCacheManager = new SegmentLocalCacheManager(
+    virtualCacheManager = new SegmentLocalCacheManager(
         virtualStorageLocations,
         virtualLoaderConfig,
         new LeastBytesUsedStorageLocationSelectorStrategy(virtualStorageLocations),
@@ -238,8 +240,12 @@ public void testLoadBootstrapSegment() throws ExecutionException, InterruptedExc
   @Test
   public void testDropSegment() throws SegmentLoadingException, ExecutionException, InterruptedException, IOException
   {
+    List<ReferenceCountedSegmentProvider> referenceProviders = new ArrayList<>();
     for (DataSegment eachSegment : SEGMENTS) {
       segmentManager.loadSegment(eachSegment);
+      ReferenceCountedSegmentProvider refProvider = cacheManager.getSegmentReferenceProvider(eachSegment);
+      referenceProviders.add(refProvider);
+      Assert.assertFalse(refProvider.isClosed());
     }
 
     final List<Future<Void>> futures = ImmutableList.of(SEGMENTS.get(0), SEGMENTS.get(2)).stream()
@@ -260,6 +266,14 @@ public void testDropSegment() throws SegmentLoadingException, ExecutionException
     assertResult(
         ImmutableList.of(SEGMENTS.get(1), SEGMENTS.get(3), SEGMENTS.get(4))
     );
+    for (int i = 0; i < SEGMENTS.size(); i++) {
+      Assert.assertEquals(0, referenceProviders.get(i).getNumReferences());
+      if (i == 0 || i == 2) {
+        Assert.assertTrue(referenceProviders.get(i).isClosed());
+      } else {
+        Assert.assertFalse(referenceProviders.get(i).isClosed());
+      }
+    }
   }
 
   private Void loadSegmentOrFail(DataSegment segment)