HBASE-23682 Fix NPE when disable DeadServerMetricRegionChore (#1026)

Signed-off-by: Bharath Vissapragada <bharathv@apache.org>

Author: binlijin

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureExecutor.java

@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.hbase.procedure2;
 
+import edu.umd.cs.findbugs.annotations.Nullable;
 import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.util.ArrayDeque;
@@ -732,7 +733,10 @@ public long getKeepAliveTime(final TimeUnit timeUnit) {
    * Add a chore procedure to the executor
    * @param chore the chore to add
    */
-  public void addChore(ProcedureInMemoryChore<TEnvironment> chore) {
+  public void addChore(@Nullable ProcedureInMemoryChore<TEnvironment> chore) {
+    if (chore == null) {
+      return;
+    }
     chore.setState(ProcedureState.WAITING_TIMEOUT);
     timeoutExecutor.add(chore);
   }
@@ -742,7 +746,10 @@ public void addChore(ProcedureInMemoryChore<TEnvironment> chore) {
    * @param chore the chore to remove
    * @return whether the chore is removed, or it will be removed later
    */
-  public boolean removeChore(ProcedureInMemoryChore<TEnvironment> chore) {
+  public boolean removeChore(@Nullable ProcedureInMemoryChore<TEnvironment> chore) {
+    if (chore == null) {
+      return true;
+    }
     chore.setState(ProcedureState.SUCCESS);
     return timeoutExecutor.remove(chore);
   }

hbase-server/src/test/java/org/apache/hadoop/hbase/master/assignment/TestDeadServerMetricRegionChore.java

@@ -0,0 +1,65 @@
+/*
+ * 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.master.assignment;
+
+import static org.junit.Assert.fail;
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.testclassification.MasterTests;
+import org.apache.hadoop.hbase.testclassification.MediumTests;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+/**
+ * Testcase for HBASE-23682.
+ */
+@Category({ MasterTests.class, MediumTests.class })
+public class TestDeadServerMetricRegionChore {
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+    HBaseClassTestRule.forClass(TestDeadServerMetricRegionChore.class);
+
+  protected HBaseTestingUtility util;
+
+  @Before
+  public void setUp() throws Exception {
+    util = new HBaseTestingUtility();
+    // Disable DeadServerMetricRegionChore
+    util.getConfiguration()
+      .setInt(AssignmentManager.DEAD_REGION_METRIC_CHORE_INTERVAL_MSEC_CONF_KEY, -1);
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    this.util.shutdownMiniCluster();
+  }
+
+  @Test
+  public void testDeadServerMetricRegionChore() throws Exception {
+    try {
+      this.util.startMiniCluster();
+    } catch (Exception e) {
+      fail("Start cluster failed");
+    }
+  }
+
+}