HBASE-18000 Make sure we always return the scanner id with ScanResponse

Signed-off-by: Andrew Purtell <apurtell@apache.org>

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

@@ -3008,6 +3008,9 @@ public class RSRpcServices implements HBaseRPCErrorHandler,
     try {
       if (request.hasScannerId()) {
         rsh = getRegionScanner(request);
+        // The downstream projects such as AsyncHBase in OpenTSDB need this value. See HBASE-18000
+        // for more details.
+        builder.setScannerId(request.getScannerId());
       } else {
         rsh = newRegionScanner(request, builder);
       }

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

@@ -0,0 +1,104 @@
+/**
+ * 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.junit.Assert.*;
+
+import java.io.IOException;
+
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.HRegionInfo;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.shaded.com.google.protobuf.ServiceException;
+import org.apache.hadoop.hbase.shaded.protobuf.RequestConverter;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos.ScanRequest;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos.ScanResponse;
+import org.apache.hadoop.hbase.testclassification.MediumTests;
+import org.apache.hadoop.hbase.testclassification.RegionServerTests;
+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;
+
+/**
+ * Testcase to make sure that we always set scanner id in ScanResponse. See HBASE-18000.
+ */
+@Category({ RegionServerTests.class, MediumTests.class })
+public class TestAlwaysSetScannerId {
+
+  private static final HBaseTestingUtility UTIL = new HBaseTestingUtility();
+
+  private static final TableName TABLE_NAME = TableName.valueOf("test");
+
+  private static final byte[] CF = Bytes.toBytes("cf");
+
+  private static final byte[] CQ = Bytes.toBytes("cq");
+
+  private static final int COUNT = 10;
+
+  private static HRegionInfo HRI;
+
+  private static ClientProtos.ClientService.BlockingInterface STUB;
+
+  @BeforeClass
+  public static void setUp() throws Exception {
+    UTIL.startMiniCluster(1);
+    try (Table table = UTIL.createTable(TABLE_NAME, CF)) {
+      for (int i = 0; i < COUNT; i++) {
+        table.put(new Put(Bytes.toBytes(i)).addColumn(CF, CQ, Bytes.toBytes(i)));
+      }
+    }
+    HRI = UTIL.getAdmin().getTableRegions(TABLE_NAME).get(0);
+    STUB = ((ConnectionImplementation) UTIL.getConnection())
+        .getClient(UTIL.getHBaseCluster().getRegionServer(0).getServerName());
+  }
+
+  @AfterClass
+  public static void tearDown() throws Exception {
+    UTIL.shutdownMiniCluster();
+  }
+
+  @Test
+  public void test() throws ServiceException, IOException {
+    Scan scan = new Scan();
+    ScanRequest req = RequestConverter.buildScanRequest(HRI.getRegionName(), scan, 1, false);
+    ScanResponse resp = STUB.scan(null, req);
+    assertTrue(resp.hasScannerId());
+    long scannerId = resp.getScannerId();
+    int nextCallSeq = 0;
+    // test next
+    for (int i = 0; i < 5; i++) {
+      req = RequestConverter.buildScanRequest(scannerId, 1, false, nextCallSeq++, false, false, -1);
+      resp = STUB.scan(null, req);
+      assertTrue(resp.hasScannerId());
+      assertEquals(scannerId, resp.getScannerId());
+    }
+    // test renew
+    req = RequestConverter.buildScanRequest(scannerId, 0, false, nextCallSeq++, false, true, -1);
+    resp = STUB.scan(null, req);
+    assertTrue(resp.hasScannerId());
+    assertEquals(scannerId, resp.getScannerId());
+    // test close
+    req = RequestConverter.buildScanRequest(scannerId, 0, true, false);
+    resp = STUB.scan(null, req);
+    assertTrue(resp.hasScannerId());
+    assertEquals(scannerId, resp.getScannerId());
+  }
+}