HBASE-26122: Implement an optional maximum size for Gets, after which…

… a partial result is returned

hbase-client/src/main/java/org/apache/hadoop/hbase/client/Get.java

@@ -75,6 +75,7 @@ public class Get extends Query implements Row {
   private TimeRange tr = TimeRange.allTime();
   private boolean checkExistenceOnly = false;
   private Map<byte [], NavigableSet<byte []>> familyMap = new TreeMap<>(Bytes.BYTES_COMPARATOR);
+  private long maxResultSize = -1;
 
   /**
    * Create a Get operation for the specified row.
@@ -281,6 +282,21 @@ public Get setFilter(Filter filter) {
     return this;
   }
 
+  /**
+   * Set the maximum result size. The default is -1; this means that no specific
+   * maximum result size will be set for this Get.
+   *
+   * If set to a value greater than zero, the server may respond with a Result where
+   * {@link Result#mayHaveMoreCellsInRow()} is true. The user is required to handle
+   * this case.
+   *
+   * @param maxResultSize The maximum result size in bytes
+   */
+  public Get setMaxResultSize(long maxResultSize) {
+    this.maxResultSize = maxResultSize;
+    return this;
+  }
+
   /* Accessors */
 
   /**
@@ -400,6 +416,13 @@ public Map<String, Object> getFingerprint() {
     return map;
   }
 
+  /**
+   * @return the maximum result size in bytes. See {@link #setMaxResultSize(long)}
+   */
+  public long getMaxResultSize() {
+    return maxResultSize;
+  }
+
   /**
    * Compile the details beyond the scope of getFingerprint (row, columns,
    * timestamps, etc.) into a Map along with the fingerprinted information.

hbase-client/src/main/java/org/apache/hadoop/hbase/shaded/protobuf/ProtobufUtil.java

@@ -640,6 +640,9 @@ public static Get toGet(final ClientProtos.Get proto) throws IOException {
     if (proto.hasLoadColumnFamiliesOnDemand()) {
       get.setLoadColumnFamiliesOnDemand(proto.getLoadColumnFamiliesOnDemand());
     }
+    if (proto.hasMaxResultSize()) {
+      get.setMaxResultSize(proto.getMaxResultSize());
+    }
     return get;
   }
 
@@ -1296,6 +1299,9 @@ public static ClientProtos.Get toGet(
     if (loadColumnFamiliesOnDemand != null) {
       builder.setLoadColumnFamiliesOnDemand(loadColumnFamiliesOnDemand);
     }
+    if (get.getMaxResultSize() > 0) {
+      builder.setMaxResultSize(get.getMaxResultSize());
+    }
     return builder.build();
   }
 
@@ -1497,6 +1503,7 @@ public static ClientProtos.Result toResultNoData(final Result result) {
     ClientProtos.Result.Builder builder = ClientProtos.Result.newBuilder();
     builder.setAssociatedCellCount(size);
     builder.setStale(result.isStale());
+    builder.setPartial(result.mayHaveMoreCellsInRow());
     return builder.build();
   }
 
@@ -1587,7 +1594,7 @@ public static Result toResult(final ClientProtos.Result proto, final CellScanner
 
     return (cells == null || cells.isEmpty())
         ? (proto.getStale() ? EMPTY_RESULT_STALE : EMPTY_RESULT)
-        : Result.create(cells, null, proto.getStale());
+        : Result.create(cells, null, proto.getStale(), proto.getPartial());
   }
 
 

hbase-protocol-shaded/src/main/protobuf/client/Client.proto

@@ -90,6 +90,8 @@ message Get {
   optional Consistency consistency = 12 [default = STRONG];
   repeated ColumnFamilyTimeRange cf_time_range = 13;
   optional bool load_column_families_on_demand = 14; /* DO NOT add defaults to load_column_families_on_demand. */
+
+  optional uint64 max_result_size = 15;
 }
 
 message Result {

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

@@ -142,6 +142,7 @@
 import org.apache.hadoop.hbase.regionserver.compactions.CompactionContext;
 import org.apache.hadoop.hbase.regionserver.compactions.CompactionLifeCycleTracker;
 import org.apache.hadoop.hbase.regionserver.compactions.ForbidMajorCompactionChecker;
+import org.apache.hadoop.hbase.regionserver.ScannerContext.LimitScope;
 import org.apache.hadoop.hbase.regionserver.throttle.CompactionThroughputControllerFactory;
 import org.apache.hadoop.hbase.regionserver.throttle.NoLimitThroughputController;
 import org.apache.hadoop.hbase.regionserver.throttle.StoreHotnessProtector;
@@ -3871,8 +3872,7 @@ public void prepareMiniBatchOperations(MiniBatchOperationInProgress<Mutation> mi
             Result result;
             if (returnResults) {
               // convert duplicate increment/append to get
-              List<Cell> results = region.get(toGet(mutation), false, nonceGroup, nonce);
-              result = Result.create(results);
+              result = region.get(toGet(mutation), false, nonceGroup, nonce);
             } else {
               result = Result.EMPTY_RESULT;
             }
@@ -7524,9 +7524,7 @@ public static boolean rowIsInRange(RegionInfo info, final byte [] row, final int
   @Override
   public Result get(final Get get) throws IOException {
     prepareGet(get);
-    List<Cell> results = get(get, true);
-    boolean stale = this.getRegionInfo().getReplicaId() != 0;
-    return Result.create(results, get.isCheckExistenceOnly() ? !results.isEmpty() : null, stale);
+    return get(get, true, HConstants.NO_NONCE, HConstants.NO_NONCE);
   }
 
   void prepareGet(final Get get) throws IOException {
@@ -7545,17 +7543,37 @@ void prepareGet(final Get get) throws IOException {
 
   @Override
   public List<Cell> get(Get get, boolean withCoprocessor) throws IOException {
-    return get(get, withCoprocessor, HConstants.NO_NONCE, HConstants.NO_NONCE);
+    return get(get, null, withCoprocessor, HConstants.NO_NONCE, HConstants.NO_NONCE);
   }
 
-  private List<Cell> get(Get get, boolean withCoprocessor, long nonceGroup, long nonce)
+  private Result get(Get get, boolean withCoprocessor, long nonceGroup, long nonce)
     throws IOException {
-    return TraceUtil.trace(() -> getInternal(get, withCoprocessor, nonceGroup, nonce),
+
+    ScannerContext scannerContext = get.getMaxResultSize() > 0
+      ? ScannerContext.newBuilder()
+          .setSizeLimit(LimitScope.BETWEEN_CELLS, get.getMaxResultSize(), get.getMaxResultSize())
+          .build()
+      : null;
+
+    List<Cell> result = get(get, scannerContext, withCoprocessor, nonceGroup, nonce);
+    boolean stale = this.getRegionInfo().getReplicaId() != 0;
+
+    return Result.create(
+      result,
+      get.isCheckExistenceOnly() ? !result.isEmpty() : null,
+      stale,
+      scannerContext != null && scannerContext.mayHaveMoreCellsInRow());
+  }
+
+  private List<Cell> get(Get get, ScannerContext scannerContext, boolean withCoprocessor,
+    long nonceGroup, long nonce) throws IOException {
+    return TraceUtil.trace(
+      () -> getInternal(get, scannerContext, withCoprocessor, nonceGroup, nonce),
       () -> createRegionSpan("Region.get"));
   }
 
-  private List<Cell> getInternal(Get get, boolean withCoprocessor, long nonceGroup, long nonce)
-    throws IOException {
+  private List<Cell> getInternal(Get get, ScannerContext scannerContext, boolean withCoprocessor,
+    long nonceGroup, long nonce) throws IOException {
     List<Cell> results = new ArrayList<>();
     long before = EnvironmentEdgeManager.currentTime();
 
@@ -7572,7 +7590,7 @@ private List<Cell> getInternal(Get get, boolean withCoprocessor, long nonceGroup
     }
     try (RegionScanner scanner = getScanner(scan, null, nonceGroup, nonce)) {
       List<Cell> tmp = new ArrayList<>();
-      scanner.next(tmp);
+      scanner.next(tmp, scannerContext);
       // 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.

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

@@ -2695,10 +2695,17 @@ private Result get(Get get, HRegion region, RegionScannersCloseCallBack closeCal
     if (scan.getLoadColumnFamiliesOnDemandValue() == null) {
       scan.setLoadColumnFamiliesOnDemand(region.isLoadingCfsOnDemandDefault());
     }
+
+    ScannerContext scannerContext = get.getMaxResultSize() > 0
+      ? ScannerContext.newBuilder()
+          .setSizeLimit(LimitScope.BETWEEN_CELLS, get.getMaxResultSize(), get.getMaxResultSize())
+          .build()
+      : null;
+
     RegionScannerImpl scanner = null;
     try {
       scanner = region.getScanner(scan);
-      scanner.next(results);
+      scanner.next(results, scannerContext);
     } finally {
       if (scanner != null) {
         if (closeCallBack == null) {
@@ -2723,7 +2730,8 @@ private Result get(Get get, HRegion region, RegionScannersCloseCallBack closeCal
     }
     region.metricsUpdateForGet(results, before);
 
-    return Result.create(results, get.isCheckExistenceOnly() ? !results.isEmpty() : null, stale);
+    return Result.create(results, get.isCheckExistenceOnly() ? !results.isEmpty() : null, stale,
+      scannerContext != null && scannerContext.mayHaveMoreCellsInRow());
   }
 
   private void checkBatchSizeAndLogLargeSize(MultiRequest request) throws ServiceException {

hbase-server/src/test/java/org/apache/hadoop/hbase/TestPartialResultsFromClientSide.java

@@ -24,20 +24,23 @@
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
-
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 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.RegionInfo;
 import org.apache.hadoop.hbase.client.Result;
 import org.apache.hadoop.hbase.client.ResultScanner;
 import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.client.Table;
+import org.apache.hadoop.hbase.filter.BinaryComparator;
 import org.apache.hadoop.hbase.filter.ColumnPrefixFilter;
 import org.apache.hadoop.hbase.filter.ColumnRangeFilter;
+import org.apache.hadoop.hbase.filter.FamilyFilter;
 import org.apache.hadoop.hbase.filter.Filter;
+import org.apache.hadoop.hbase.filter.FilterList;
 import org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter;
 import org.apache.hadoop.hbase.filter.FirstKeyValueMatchingQualifiersFilter;
 import org.apache.hadoop.hbase.filter.RandomRowFilter;
@@ -134,6 +137,46 @@ public static void tearDownAfterClass() throws Exception {
     TEST_UTIL.shutdownMiniCluster();
   }
 
+  @Test
+  public void testGetPartialResults() throws Exception {
+    byte[] row = ROWS[0];
+
+    Result result;
+    int cf = 0;
+    int qf = 0;
+    int total = 0;
+
+    do {
+      // this will ensure we always return only 1 result
+      Get get = new Get(row)
+        .setMaxResultSize(1);
+
+      // we want to page through the entire row, this will ensure we always get the next
+      if (total > 0) {
+        get.setFilter(new FilterList(FilterList.Operator.MUST_PASS_ALL,
+          new ColumnRangeFilter(QUALIFIERS[qf], true, null, false),
+          new FamilyFilter(CompareOperator.GREATER_OR_EQUAL, new BinaryComparator(FAMILIES[cf]))));
+      }
+
+      // all values are the same, but there should be a value
+      result = TABLE.get(get);
+      assertTrue(String.format("Value for family %s (# %s) and qualifier %s (# %s)",
+        Bytes.toStringBinary(FAMILIES[cf]), cf, Bytes.toStringBinary(QUALIFIERS[qf]), qf),
+        Bytes.equals(VALUE, result.getValue(FAMILIES[cf], QUALIFIERS[qf])));
+
+      total++;
+      if (++qf >= NUM_QUALIFIERS) {
+        cf++;
+        qf = 0;
+      }
+    } while (result.mayHaveMoreCellsInRow());
+
+    // ensure we iterated all cells in row
+    assertEquals(NUM_COLS, total);
+    assertEquals(NUM_FAMILIES, cf);
+    assertEquals(0, qf);
+  }
+
   /**
    * Ensure that the expected key values appear in a result returned from a scanner that is
    * combining partial results into complete results

hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegion.java

@@ -7879,4 +7879,89 @@ public void run() {
     assertFalse("Region lock holder should not have been interrupted", holderInterrupted.get());
   }
 
+  @Test
+  public void testOversizedGetsReturnPartialResult() throws IOException {
+    HRegion region = initHRegion(tableName, name.getMethodName(), CONF, fam1);
+
+    Put p = new Put(row)
+      .addColumn(fam1, qual1, value1)
+      .addColumn(fam1, qual2, value2);
+
+    region.put(p);
+
+    Get get = new Get(row)
+      .addColumn(fam1, qual1)
+      .addColumn(fam1, qual2)
+      .setMaxResultSize(1); // 0 doesn't count as a limit, according to HBase
+
+    Result r = region.get(get);
+
+    assertTrue("Expected partial result, but result was not marked as partial", r.mayHaveMoreCellsInRow());
+  }
+
+  @Test
+  public void testGetsWithoutResultSizeLimitAreNotPartial() throws IOException {
+    HRegion region = initHRegion(tableName, name.getMethodName(), CONF, fam1);
+
+    Put p = new Put(row)
+      .addColumn(fam1, qual1, value1)
+      .addColumn(fam1, qual2, value2);
+
+    region.put(p);
+
+    Get get = new Get(row)
+      .addColumn(fam1, qual1)
+      .addColumn(fam1, qual2);
+
+    Result r = region.get(get);
+
+    assertFalse("Expected full result, but it was marked as partial", r.mayHaveMoreCellsInRow());
+    assertTrue(Bytes.equals(value1, r.getValue(fam1, qual1)));
+    assertTrue(Bytes.equals(value2, r.getValue(fam1, qual2)));
+  }
+
+  @Test
+  public void testGetsWithinResultSizeLimitAreNotPartial() throws IOException {
+    HRegion region = initHRegion(tableName, name.getMethodName(), CONF, fam1);
+
+    Put p = new Put(row)
+      .addColumn(fam1, qual1, value1)
+      .addColumn(fam1, qual2, value2);
+
+    region.put(p);
+
+    Get get = new Get(row)
+      .addColumn(fam1, qual1)
+      .addColumn(fam1, qual2)
+      .setMaxResultSize(Long.MAX_VALUE);
+
+    Result r = region.get(get);
+
+    assertFalse("Expected full result, but it was marked as partial", r.mayHaveMoreCellsInRow());
+    assertTrue(Bytes.equals(value1, r.getValue(fam1, qual1)));
+    assertTrue(Bytes.equals(value2, r.getValue(fam1, qual2)));
+  }
+
+  @Test
+  public void testGetsWithResultSizeLimitReturnPartialResults() throws IOException {
+    HRegion region = initHRegion(tableName, name.getMethodName(), CONF, fam1);
+
+    Put p = new Put(row)
+      .addColumn(fam1, qual1, value1)
+      .addColumn(fam1, qual2, value2);
+
+    region.put(p);
+
+    Get get = new Get(row)
+      .addColumn(fam1, qual1)
+      .addColumn(fam1, qual2)
+      .setMaxResultSize(10);
+
+    Result r = region.get(get);
+
+    assertTrue("Expected partial result, but it was marked as complete", r.mayHaveMoreCellsInRow());
+    assertTrue(Bytes.equals(value1, r.getValue(fam1, qual1)));
+    assertEquals("Got more results than expected", 1, r.size());
+  }
+
 }