HBASE-18267 The result from the postAppend is ignored

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

@@ -691,7 +691,7 @@ public class RSRpcServices implements HBaseRPCErrorHandler,
         }
       }
       if (region.getCoprocessorHost() != null) {
-        region.getCoprocessorHost().postAppend(append, r);
+        r = region.getCoprocessorHost().postAppend(append, r);
       }
     }
     if (regionServer.metricsRegionServer != null) {

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

@@ -1226,12 +1226,13 @@ public class RegionCoprocessorHost
    * @param result the result returned by the append
    * @throws IOException if an error occurred on the coprocessor
    */
-  public void postAppend(final Append append, final Result result) throws IOException {
-    execOperation(coprocessors.isEmpty() ? null : new RegionOperation() {
+  public Result postAppend(final Append append, final Result result) throws IOException {
+    return execOperationWithResult(result,
+        coprocessors.isEmpty() ? null : new RegionOperationWithResult<Result>() {
       @Override
       public void call(RegionObserver oserver, ObserverContext<RegionCoprocessorEnvironment> ctx)
           throws IOException {
-        oserver.postAppend(ctx, append, result);
+        setResult(oserver.postAppend(ctx, append, result));
       }
     });
   }

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

@@ -0,0 +1,127 @@
+/**
+ * Copyright The Apache Software Foundation
+ *
+ * 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 java.io.IOException;
+import java.util.Arrays;
+import static junit.framework.TestCase.assertTrue;
+import org.apache.hadoop.hbase.Cell;
+import org.apache.hadoop.hbase.CellUtil;
+import org.apache.hadoop.hbase.CoprocessorEnvironment;
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.KeyValue;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
+import org.apache.hadoop.hbase.coprocessor.RegionObserver;
+import org.apache.hadoop.hbase.testclassification.ClientTests;
+import org.apache.hadoop.hbase.testclassification.MediumTests;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+@Category({MediumTests.class, ClientTests.class})
+public class TestResultFromCoprocessor {
+  private static final HBaseTestingUtility TEST_UTIL = new HBaseTestingUtility();
+  private static final byte[] ROW = Bytes.toBytes("normal_row");
+  private static final byte[] FAMILY = Bytes.toBytes("fm");
+  private static final byte[] QUAL = Bytes.toBytes("qual");
+  private static final byte[] VALUE = Bytes.toBytes(100L);
+  private static final byte[] FIXED_VALUE = Bytes.toBytes("fixed_value");
+  private static final Cell FIXED_CELL = CellUtil.createCell(ROW, FAMILY,
+          QUAL, 0, KeyValue.Type.Put.getCode(), FIXED_VALUE);
+  private static final Result FIXED_RESULT = Result.create(Arrays.asList(FIXED_CELL));
+  private static final TableName TABLE_NAME = TableName.valueOf("TestResultFromCoprocessor");
+  @BeforeClass
+  public static void setUpBeforeClass() throws Exception {
+    TEST_UTIL.startMiniCluster(3);
+    TableDescriptor desc = TableDescriptorBuilder.newBuilder(TABLE_NAME)
+            .addCoprocessor(MyObserver.class.getName())
+            .addColumnFamily(ColumnFamilyDescriptorBuilder.newBuilder(FAMILY).build())
+            .build();
+    TEST_UTIL.getAdmin().createTable(desc);
+  }
+
+  @AfterClass
+  public static void tearDownAfterClass() throws Exception {
+    TEST_UTIL.shutdownMiniCluster();
+  }
+
+  @Test
+  public void testAppend() throws IOException {
+    try (Table t = TEST_UTIL.getConnection().getTable(TABLE_NAME)) {
+      Put put = new Put(ROW);
+      put.addColumn(FAMILY, QUAL, VALUE);
+      t.put(put);
+      assertRowAndValue(t.get(new Get(ROW)), ROW, VALUE);
+      Append append = new Append(ROW);
+      append.add(FAMILY, QUAL, FIXED_VALUE);
+      assertRowAndValue(t.append(append), ROW, FIXED_VALUE);
+      assertRowAndValue(t.get(new Get(ROW)), ROW, Bytes.add(VALUE, FIXED_VALUE));
+    }
+  }
+
+  @Test
+  public void testIncrement() throws IOException {
+    try (Table t = TEST_UTIL.getConnection().getTable(TABLE_NAME)) {
+      Put put = new Put(ROW);
+      put.addColumn(FAMILY, QUAL, VALUE);
+      t.put(put);
+      assertRowAndValue(t.get(new Get(ROW)), ROW, VALUE);
+      Increment inc = new Increment(ROW);
+      inc.addColumn(FAMILY, QUAL, 99);
+      assertRowAndValue(t.increment(inc), ROW, FIXED_VALUE);
+      assertRowAndValue(t.get(new Get(ROW)), ROW, Bytes.toBytes(199L));
+    }
+  }
+
+  private static void assertRowAndValue(Result r, byte[] row, byte[] value) {
+    for (Cell c : r.rawCells()) {
+      assertTrue(Bytes.equals(CellUtil.cloneRow(c), row));
+      assertTrue(Bytes.equals(CellUtil.cloneValue(c), value));
+    }
+  }
+
+  public static class MyObserver implements RegionObserver {
+
+    @Override
+    public Result postAppend(final ObserverContext<RegionCoprocessorEnvironment> c,
+      final Append append, final Result result) {
+      return FIXED_RESULT;
+    }
+
+    @Override
+    public Result postIncrement(final ObserverContext<RegionCoprocessorEnvironment> c,
+      final Increment increment, final Result result) {
+      return FIXED_RESULT;
+    }
+
+    @Override
+    public void start(CoprocessorEnvironment env) throws IOException {
+    }
+
+    @Override
+    public void stop(CoprocessorEnvironment env) throws IOException {
+    }
+  }
+
+}