HBASE-26036 DBB released too early in HRegion.get() and dirty data for some operations (#3436)

Signed-off-by: Michael Stack <stack@apache.org>

hbase-common/src/main/java/org/apache/hadoop/hbase/io/ByteBuffAllocator.java

@@ -29,6 +29,7 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.nio.ByteBuff;
 import org.apache.hadoop.hbase.nio.SingleByteBuff;
+import org.apache.hadoop.hbase.util.ReflectionUtils;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -70,6 +71,13 @@ public class ByteBuffAllocator {
 
   public static final String MIN_ALLOCATE_SIZE_KEY = "hbase.server.allocator.minimal.allocate.size";
 
+  /**
+   * Set an alternate bytebuffallocator by setting this config,
+   * e.g. we can config {@link DeallocateRewriteByteBuffAllocator} to find out
+   * prematurely release issues
+   */
+  public static final String BYTEBUFF_ALLOCATOR_CLASS = "hbase.bytebuff.allocator.class";
+
   /**
    * @deprecated since 2.3.0 and will be removed in 4.0.0. Use
    *   {@link ByteBuffAllocator#ALLOCATOR_POOL_ENABLED_KEY} instead.
@@ -117,8 +125,8 @@ public class ByteBuffAllocator {
     void free();
   }
 
-  private final boolean reservoirEnabled;
+  protected final boolean reservoirEnabled;
-  private final int bufSize;
+  protected final int bufSize;
   private final int maxBufCount;
   private final AtomicInteger usedBufCount = new AtomicInteger(0);
 
@@ -169,7 +177,9 @@ public class ByteBuffAllocator {
           conf.getInt(MAX_BUFFER_COUNT_KEY, conf.getInt(HConstants.REGION_SERVER_HANDLER_COUNT,
             HConstants.DEFAULT_REGION_SERVER_HANDLER_COUNT) * bufsForTwoMB * 2);
       int minSizeForReservoirUse = conf.getInt(MIN_ALLOCATE_SIZE_KEY, poolBufSize / 6);
-      return new ByteBuffAllocator(true, maxBuffCount, poolBufSize, minSizeForReservoirUse);
+      Class<?> clazz = conf.getClass(BYTEBUFF_ALLOCATOR_CLASS, ByteBuffAllocator.class);
+      return (ByteBuffAllocator) ReflectionUtils
+        .newInstance(clazz, true, maxBuffCount, poolBufSize, minSizeForReservoirUse);
     } else {
       return HEAP;
     }
@@ -184,7 +194,7 @@ public class ByteBuffAllocator {
     return new ByteBuffAllocator(false, 0, DEFAULT_BUFFER_SIZE, Integer.MAX_VALUE);
   }
 
-  ByteBuffAllocator(boolean reservoirEnabled, int maxBufCount, int bufSize,
+  protected ByteBuffAllocator(boolean reservoirEnabled, int maxBufCount, int bufSize,
     int minSizeForReservoirUse) {
     this.reservoirEnabled = reservoirEnabled;
     this.maxBufCount = maxBufCount;
@@ -377,7 +387,7 @@ public class ByteBuffAllocator {
    * Return back a ByteBuffer after its use. Don't read/write the ByteBuffer after the returning.
    * @param buf ByteBuffer to return.
    */
-  private void putbackBuffer(ByteBuffer buf) {
+  protected void putbackBuffer(ByteBuffer buf) {
     if (buf.capacity() != bufSize || (reservoirEnabled ^ buf.isDirect())) {
       LOG.warn("Trying to put a buffer, not created by this pool! Will be just ignored");
       return;

hbase-common/src/main/java/org/apache/hadoop/hbase/io/DeallocateRewriteByteBuffAllocator.java

@@ -0,0 +1,59 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hbase.io;
+
+import java.nio.ByteBuffer;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A ByteBuffAllocator that rewrite the bytebuffers right after released.
+ * It can be used for test whether there are prematurely releasing backing bytebuffers.
+ */
+@InterfaceAudience.Private
+public class DeallocateRewriteByteBuffAllocator  extends ByteBuffAllocator {
+  private static final Logger LOG = LoggerFactory.getLogger(
+    DeallocateRewriteByteBuffAllocator.class);
+
+  DeallocateRewriteByteBuffAllocator(boolean reservoirEnabled, int maxBufCount, int bufSize,
+    int minSizeForReservoirUse) {
+    super(reservoirEnabled, maxBufCount, bufSize, minSizeForReservoirUse);
+  }
+
+  @Override
+  protected void putbackBuffer(ByteBuffer buf) {
+    if (buf.capacity() != bufSize || (reservoirEnabled ^ buf.isDirect())) {
+      LOG.warn("Trying to put a buffer, not created by this pool! Will be just ignored");
+      return;
+    }
+    buf.clear();
+    byte[] tmp = generateTmpBytes(buf.capacity());
+    buf.put(tmp, 0, tmp.length);
+    super.putbackBuffer(buf);
+  }
+
+  private byte[] generateTmpBytes(int length) {
+    StringBuilder result = new StringBuilder();
+    while (result.length() < length) {
+      result.append("-");
+    }
+    return Bytes.toBytes(result.substring(0, length));
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/MultiRowMutationEndpoint.java

@@ -33,6 +33,7 @@ import org.apache.hadoop.hbase.PrivateCellUtil;
 import org.apache.hadoop.hbase.client.Get;
 import org.apache.hadoop.hbase.client.Mutation;
 import org.apache.hadoop.hbase.client.RegionInfo;
+import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.filter.ByteArrayComparable;
 import org.apache.hadoop.hbase.filter.Filter;
 import org.apache.hadoop.hbase.io.TimeRange;
@@ -40,6 +41,7 @@ import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
 import org.apache.hadoop.hbase.regionserver.HRegion;
 import org.apache.hadoop.hbase.regionserver.NoSuchColumnFamilyException;
 import org.apache.hadoop.hbase.regionserver.Region;
+import org.apache.hadoop.hbase.regionserver.RegionScanner;
 import org.apache.hadoop.hbase.regionserver.WrongRegionException;
 import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.yetus.audience.InterfaceAudience;
@@ -221,8 +223,12 @@ public class MultiRowMutationEndpoint extends MultiRowMutationService implements
       get.setTimeRange(timeRange.getMin(), timeRange.getMax());
     }
 
-    List<Cell> result = region.get(get, false);
     boolean matches = false;
+    try (RegionScanner scanner = region.getScanner(new Scan(get))) {
+      // NOTE: Please don't use HRegion.get() instead,
+      // because it will copy cells to heap. See HBASE-26036
+      List<Cell> result = new ArrayList<>();
+      scanner.next(result);
       if (filter != null) {
         if (!result.isEmpty()) {
           matches = true;
@@ -239,6 +245,7 @@ public class MultiRowMutationEndpoint extends MultiRowMutationService implements
           matches = matches(op, compareResult);
         }
       }
+    }
     return matches;
   }
 

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java

@@ -20,7 +20,6 @@ package org.apache.hadoop.hbase.regionserver;
 import static org.apache.hadoop.hbase.HConstants.REPLICATION_SCOPE_LOCAL;
 import static org.apache.hadoop.hbase.regionserver.HStoreFile.MAJOR_COMPACTION_KEY;
 import static org.apache.hadoop.hbase.util.ConcurrentMapUtils.computeIfAbsent;
-
 import edu.umd.cs.findbugs.annotations.Nullable;
 import io.opentelemetry.api.trace.Span;
 import java.io.EOFException;
@@ -74,6 +73,7 @@ import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.LocatedFileStatus;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.ByteBufferExtendedCell;
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellBuilderType;
 import org.apache.hadoop.hbase.CellComparator;
@@ -176,7 +176,6 @@ import org.apache.hadoop.util.StringUtils;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-
 import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;
 import org.apache.hbase.thirdparty.com.google.common.collect.Iterables;
 import org.apache.hbase.thirdparty.com.google.common.collect.Lists;
@@ -191,7 +190,6 @@ import org.apache.hbase.thirdparty.com.google.protobuf.Service;
 import org.apache.hbase.thirdparty.com.google.protobuf.TextFormat;
 import org.apache.hbase.thirdparty.com.google.protobuf.UnsafeByteOperations;
 import org.apache.hbase.thirdparty.org.apache.commons.collections4.CollectionUtils;
-
 import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos.CoprocessorServiceCall;
@@ -3244,7 +3242,11 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
 
   private void updateDeleteLatestVersionTimestamp(Cell cell, Get get, int count, byte[] byteNow)
       throws IOException {
-    List<Cell> result = get(get, false);
+    try (RegionScanner scanner = getScanner(new Scan(get))) {
+      // NOTE: Please don't use HRegion.get() instead,
+      // because it will copy cells to heap. See HBASE-26036
+      List<Cell> result = new ArrayList<>();
+      scanner.next(result);
 
       if (result.size() < count) {
         // Nothing to delete
@@ -3257,6 +3259,7 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
       Cell getCell = result.get(count - 1);
       PrivateCellUtil.setTimestamp(cell, getCell.getTimestamp());
     }
+  }
 
   @Override
   public void put(Put put) throws IOException {
@@ -4044,16 +4047,19 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
         get.setTimeRange(tr.getMin(), tr.getMax());
       }
 
-      List<Cell> currentValues = region.get(get, false);
+      try (RegionScanner scanner = region.getScanner(new Scan(get))) {
-
+        // NOTE: Please don't use HRegion.get() instead,
+        // because it will copy cells to heap. See HBASE-26036
+        List<Cell> currentValues = new ArrayList<>();
+        scanner.next(currentValues);
         // Iterate the input columns and update existing values if they were found, otherwise
         // add new column initialized to the delta amount
         int currentValuesIndex = 0;
         for (int i = 0; i < deltas.size(); i++) {
           Cell delta = deltas.get(i);
           Cell currentValue = null;
-        if (currentValuesIndex < currentValues.size() &&
+          if (currentValuesIndex < currentValues.size() && CellUtil
-          CellUtil.matchingQualifier(currentValues.get(currentValuesIndex), delta)) {
+            .matchingQualifier(currentValues.get(currentValuesIndex), delta)) {
             currentValue = currentValues.get(currentValuesIndex);
             if (i < (deltas.size() - 1) && !CellUtil.matchingQualifier(delta, deltas.get(i + 1))) {
               currentValuesIndex++;
@@ -4063,24 +4069,24 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
           Cell newCell;
           if (mutation instanceof Increment) {
             long deltaAmount = getLongValue(delta);
-          final long newValue = currentValue == null ?
+            final long newValue = currentValue == null ? deltaAmount :
-            deltaAmount : getLongValue(currentValue) + deltaAmount;
+              getLongValue(currentValue) + deltaAmount;
             newCell = reckonDelta(delta, currentValue, columnFamily, now, mutation,
               (oldCell) -> Bytes.toBytes(newValue));
           } else {
             newCell = reckonDelta(delta, currentValue, columnFamily, now, mutation,
-            (oldCell) ->
+              (oldCell) -> ByteBuffer.wrap(new byte[delta.getValueLength() +
-              ByteBuffer.wrap(new byte[delta.getValueLength() + oldCell.getValueLength()])
+                oldCell.getValueLength()])
                 .put(oldCell.getValueArray(), oldCell.getValueOffset(), oldCell.getValueLength())
                 .put(delta.getValueArray(), delta.getValueOffset(), delta.getValueLength())
-                .array()
+                .array());
-          );
           }
           if (region.maxCellSize > 0) {
             int newCellSize = PrivateCellUtil.estimatedSerializedSizeOf(newCell);
             if (newCellSize > region.maxCellSize) {
-            String msg = "Cell with size " + newCellSize + " exceeds limit of "
+              String msg =
-              + region.maxCellSize + " bytes in region " + this;
+                "Cell with size " + newCellSize + " exceeds limit of " + region.maxCellSize +
+                  " bytes in region " + this;
               LOG.debug(msg);
               throw new DoNotRetryIOException(msg);
             }
@@ -4098,6 +4104,7 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
             region.coprocessorHost.postIncrementBeforeWAL(mutation, cellPairs) :
             region.coprocessorHost.postAppendBeforeWAL(mutation, cellPairs);
         }
+      }
       return cellPairs.stream().map(Pair::getSecond).collect(Collectors.toList());
     }
 
@@ -4858,16 +4865,21 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
         // NOTE: We used to wait here until mvcc caught up: mvcc.await();
         // Supposition is that now all changes are done under row locks, then when we go to read,
         // we'll get the latest on this row.
-        List<Cell> result = get(get, false);
         boolean matches = false;
         long cellTs = 0;
+        try (RegionScanner scanner = getScanner(new Scan(get))) {
+          // NOTE: Please don't use HRegion.get() instead,
+          // because it will copy cells to heap. See HBASE-26036
+          List<Cell> result = new ArrayList<>(1);
+          scanner.next(result);
           if (filter != null) {
             if (!result.isEmpty()) {
               matches = true;
               cellTs = result.get(0).getTimestamp();
             }
           } else {
-          boolean valueIsNull = comparator.getValue() == null || comparator.getValue().length == 0;
+            boolean valueIsNull =
+              comparator.getValue() == null || comparator.getValue().length == 0;
             if (result.isEmpty() && valueIsNull) {
               matches = true;
             } else if (result.size() > 0 && result.get(0).getValueLength() == 0 && valueIsNull) {
@@ -4880,6 +4892,7 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
               matches = matches(op, compareResult);
             }
           }
+        }
 
         // If matches, perform the mutation or the rowMutations
         if (matches) {
@@ -7558,7 +7571,15 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
       scan.setLoadColumnFamiliesOnDemand(isLoadingCfsOnDemandDefault());
     }
     try (RegionScanner scanner = getScanner(scan, null, nonceGroup, nonce)) {
-      scanner.next(results);
+      List<Cell> tmp = new ArrayList<>();
+      scanner.next(tmp);
+      // Copy EC to heap, then close the scanner.
+      // This can be an EXPENSIVE call. It may make an extra copy from offheap to onheap buffers.
+      // See more details in HBASE-26036.
+      for (Cell cell : tmp) {
+        results.add(cell instanceof ByteBufferExtendedCell ?
+          ((ByteBufferExtendedCell) cell).deepClone(): cell);
+      }
     }
 
     // post-get CP hook

hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/VisibilityController.java

@@ -397,7 +397,11 @@ public class VisibilityController implements MasterCoprocessor, RegionCoprocesso
     }
     get.setFilter(new DeleteVersionVisibilityExpressionFilter(visibilityTags,
         VisibilityConstants.SORTED_ORDINAL_SERIALIZATION_FORMAT));
-    List<Cell> result = ctx.getEnvironment().getRegion().get(get, false);
+    try (RegionScanner scanner = ctx.getEnvironment().getRegion().getScanner(new Scan(get))) {
+      // NOTE: Please don't use HRegion.get() instead,
+      // because it will copy cells to heap. See HBASE-26036
+      List<Cell> result = new ArrayList<>();
+      scanner.next(result);
 
       if (result.size() < get.getMaxVersions()) {
         // Nothing to delete
@@ -405,12 +409,12 @@ public class VisibilityController implements MasterCoprocessor, RegionCoprocesso
         return;
       }
       if (result.size() > get.getMaxVersions()) {
-      throw new RuntimeException("Unexpected size: " + result.size()
+        throw new RuntimeException("Unexpected size: " + result.size() +
-          + ". Results more than the max versions obtained.");
+          ". Results more than the max versions obtained.");
       }
       Cell getCell = result.get(get.getMaxVersions() - 1);
       PrivateCellUtil.setTimestamp(cell, getCell.getTimestamp());
-
+    }
     // We are bypassing here because in the HRegion.updateDeleteLatestVersionTimeStamp we would
     // update with the current timestamp after again doing a get. As the hook as already determined
     // the needed timestamp we need to bypass here.

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestCheckAndMutateWithByteBuff.java

@@ -0,0 +1,135 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hbase.client;
+
+import static org.apache.hadoop.hbase.util.Threads.sleep;
+import static org.junit.Assert.assertTrue;
+import java.io.IOException;
+import java.util.List;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.Cell;
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.io.ByteBuffAllocator;
+import org.apache.hadoop.hbase.io.DeallocateRewriteByteBuffAllocator;
+import org.apache.hadoop.hbase.io.hfile.BlockCacheFactory;
+import org.apache.hadoop.hbase.regionserver.HRegion;
+import org.apache.hadoop.hbase.regionserver.HRegionFileSystem;
+import org.apache.hadoop.hbase.regionserver.RegionServerServices;
+import org.apache.hadoop.hbase.testclassification.LargeTests;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.hbase.wal.WAL;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.junit.rules.TestName;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+@Category(LargeTests.class)
+public class TestCheckAndMutateWithByteBuff {
+  private static final Logger LOG = LoggerFactory.getLogger(TestCheckAndMutateWithByteBuff.class);
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+    HBaseClassTestRule.forClass(TestCheckAndMutateWithByteBuff.class);
+
+  @Rule
+  public TestName name = new TestName();
+
+  private static final byte[] CF = Bytes.toBytes("CF");
+  private static final HBaseTestingUtility TEST_UTIL = new HBaseTestingUtility();
+  private static final Configuration conf = TEST_UTIL.getConfiguration();
+  private static Admin admin = null;
+
+  @BeforeClass
+  public static void setupBeforeClass() throws Exception {
+    conf.set(HConstants.REGION_IMPL, TestCheckAndMutateRegion.class.getName());
+    conf.set(ByteBuffAllocator.BYTEBUFF_ALLOCATOR_CLASS,
+      DeallocateRewriteByteBuffAllocator.class.getName());
+    conf.setBoolean(ByteBuffAllocator.ALLOCATOR_POOL_ENABLED_KEY, true);
+    conf.setInt(ByteBuffAllocator.MIN_ALLOCATE_SIZE_KEY, 1);
+    conf.setInt(BlockCacheFactory.BUCKET_CACHE_WRITER_THREADS_KEY, 20);
+    conf.setInt(ByteBuffAllocator.BUFFER_SIZE_KEY, 1024);
+    conf.set(HConstants.BUCKET_CACHE_IOENGINE_KEY, "offheap");
+    conf.setInt(HConstants.BUCKET_CACHE_SIZE_KEY, 64);
+    conf.setInt("hbase.client.retries.number", 1);
+    TEST_UTIL.startMiniCluster();
+    admin = TEST_UTIL.getAdmin();
+  }
+
+  @AfterClass
+  public static void tearDownAfterClass() throws Exception {
+    TEST_UTIL.shutdownMiniCluster();
+  }
+
+  @Test
+  public void testCheckAndMutateWithByteBuff() throws Exception {
+    Table testTable = createTable(TableName.valueOf(name.getMethodName()));
+    byte[] checkRow = Bytes.toBytes("checkRow");
+    byte[] checkQualifier = Bytes.toBytes("cq");
+    byte[] checkValue = Bytes.toBytes("checkValue");
+
+    Put put = new Put(checkRow);
+    put.addColumn(CF, checkQualifier, checkValue);
+    testTable.put(put);
+    admin.flush(testTable.getName());
+
+    assertTrue(testTable.checkAndMutate(checkRow, CF).qualifier(checkQualifier).
+      ifEquals(checkValue)
+      .thenPut(new Put(checkRow).addColumn(CF, Bytes.toBytes("q1"),
+        Bytes.toBytes("testValue"))));
+  }
+
+  private Table createTable(TableName tableName)
+    throws IOException {
+    TableDescriptor td = TableDescriptorBuilder.newBuilder(tableName)
+      .setColumnFamily(ColumnFamilyDescriptorBuilder.newBuilder(CF).setBlocksize(100).build())
+      .build();
+    return TEST_UTIL.createTable(td, null);
+  }
+
+  /**
+   * An override of HRegion to allow sleep after get(), waiting for the release of DBB
+   */
+  public static class TestCheckAndMutateRegion extends HRegion {
+    public TestCheckAndMutateRegion(Path tableDir, WAL log, FileSystem fs, Configuration confParam,
+      RegionInfo info, TableDescriptor htd, RegionServerServices rsServices) {
+      super(tableDir, log, fs, confParam, info, htd, rsServices);
+    }
+
+    public TestCheckAndMutateRegion(HRegionFileSystem fs, WAL wal, Configuration confParam,
+      TableDescriptor htd, RegionServerServices rsServices) {
+      super(fs, wal, confParam, htd, rsServices);
+    }
+
+    @Override
+    public List<Cell> get(Get get, boolean withCoprocessor) throws IOException {
+      List<Cell> cells = super.get(get, withCoprocessor);
+      sleep(600);
+      return cells;
+    }
+  }
+}

hbase-server/src/test/java/org/apache/hadoop/hbase/security/visibility/ExpAsStringVisibilityLabelServiceImpl.java

@@ -21,7 +21,6 @@ import static org.apache.hadoop.hbase.TagType.VISIBILITY_TAG_TYPE;
 import static org.apache.hadoop.hbase.security.visibility.VisibilityConstants.LABELS_TABLE_FAMILY;
 import static org.apache.hadoop.hbase.security.visibility.VisibilityConstants.LABELS_TABLE_NAME;
 import static org.apache.hadoop.hbase.security.visibility.VisibilityUtils.SYSTEM_LABEL;
-
 import java.io.ByteArrayOutputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
@@ -31,7 +30,6 @@ import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
-
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.ArrayBackedTag;
 import org.apache.hadoop.hbase.AuthUtil;
@@ -49,10 +47,12 @@ import org.apache.hadoop.hbase.client.Delete;
 import org.apache.hadoop.hbase.client.Get;
 import org.apache.hadoop.hbase.client.Put;
 import org.apache.hadoop.hbase.client.Result;
+import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.client.Table;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.regionserver.OperationStatus;
 import org.apache.hadoop.hbase.regionserver.Region;
+import org.apache.hadoop.hbase.regionserver.RegionScanner;
 import org.apache.hadoop.hbase.security.Superusers;
 import org.apache.hadoop.hbase.security.User;
 import org.apache.hadoop.hbase.security.visibility.expression.ExpressionNode;
@@ -164,7 +164,27 @@ public class ExpAsStringVisibilityLabelServiceImpl implements VisibilityLabelSer
     assert (labelsRegion != null || systemCall);
     List<String> auths = new ArrayList<>();
     Get get = new Get(user);
-    List<Cell> cells = null;
+    getAuths(get, auths);
+    return auths;
+  }
+
+  @Override
+  public List<String> getGroupAuths(String[] groups, boolean systemCall) throws IOException {
+    assert (labelsRegion != null || systemCall);
+    List<String> auths = new ArrayList<>();
+    if (groups != null && groups.length > 0) {
+      for (String group : groups) {
+        Get get = new Get(Bytes.toBytes(AuthUtil.toGroupEntry(group)));
+        getAuths(get, auths);
+      }
+    }
+    return auths;
+  }
+
+  private void getAuths(Get get, List<String> auths) throws IOException {
+    List<Cell> cells = new ArrayList<>();
+    RegionScanner scanner = null;
+    try {
       if (labelsRegion == null) {
         Table table = null;
         Connection connection = null;
@@ -182,53 +202,21 @@ public class ExpAsStringVisibilityLabelServiceImpl implements VisibilityLabelSer
           }
         }
       } else {
-      cells = this.labelsRegion.get(get, false);
+        // NOTE: Please don't use HRegion.get() instead,
+        // because it will copy cells to heap. See HBASE-26036
+        scanner = this.labelsRegion.getScanner(new Scan(get));
+        scanner.next(cells);
       }
-    if (cells != null) {
       for (Cell cell : cells) {
-        String auth = Bytes.toString(cell.getQualifierArray(), cell.getQualifierOffset(),
+        String auth = Bytes
-          cell.getQualifierLength());
+          .toString(cell.getQualifierArray(), cell.getQualifierOffset(), cell.getQualifierLength());
         auths.add(auth);
       }
-    }
-    return auths;
-  }
-
-  @Override
-  public List<String> getGroupAuths(String[] groups, boolean systemCall) throws IOException {
-    assert (labelsRegion != null || systemCall);
-    List<String> auths = new ArrayList<>();
-    if (groups != null && groups.length > 0) {
-      for (String group : groups) {
-        Get get = new Get(Bytes.toBytes(AuthUtil.toGroupEntry(group)));
-        List<Cell> cells = null;
-        if (labelsRegion == null) {
-          Table table = null;
-          Connection connection = null;
-          try {
-            connection = ConnectionFactory.createConnection(conf);
-            table = connection.getTable(VisibilityConstants.LABELS_TABLE_NAME);
-            Result result = table.get(get);
-            cells = result.listCells();
     } finally {
-            if (table != null) {
+      if (scanner != null) {
-              table.close();
+        scanner.close();
-              connection.close();
       }
     }
-        } else {
-          cells = this.labelsRegion.get(get, false);
-        }
-        if (cells != null) {
-          for (Cell cell : cells) {
-            String auth = Bytes.toString(cell.getQualifierArray(), cell.getQualifierOffset(),
-              cell.getQualifierLength());
-            auths.add(auth);
-          }
-        }
-      }
-    }
-    return auths;
   }
 
   @Override