HBASE-22738 Fallback to default group to choose RS when there are no RS in current group (#1789)

Signed-off-by: Guanghao Zhang <zghao@apache.org>

hbase-server/src/main/java/org/apache/hadoop/hbase/rsgroup/RSGroupBasedLoadBalancer.java

@@ -19,12 +19,15 @@ package org.apache.hadoop.hbase.rsgroup;
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeMap;
+
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.ClusterMetrics;
 import org.apache.hadoop.hbase.HBaseIOException;
@@ -77,6 +80,17 @@ public class RSGroupBasedLoadBalancer implements LoadBalancer {
   private volatile RSGroupInfoManager rsGroupInfoManager;
   private LoadBalancer internalBalancer;
 
+  /**
+   * Define the config key of fallback groups
+   * Enabled only if this property is set
+   * Please keep balancer switch on at the same time, which is relied on to correct misplaced
+   * regions
+   */
+  public static final String FALLBACK_GROUPS_KEY = "hbase.rsgroup.fallback.groups";
+
+  private boolean fallbackEnabled = false;
+  private Set<String> fallbackGroups;
+
   /**
    * Used by reflection in {@link org.apache.hadoop.hbase.master.balancer.LoadBalancerFactory}.
    */
@@ -200,11 +214,14 @@ public class RSGroupBasedLoadBalancer implements LoadBalancer {
               .orElse(defaultInfo).getName();
         groupToRegion.put(groupName, region);
       }
-      for (String key : groupToRegion.keySet()) {
+      for (String group : groupToRegion.keySet()) {
         Map<RegionInfo, ServerName> currentAssignmentMap = new TreeMap<RegionInfo, ServerName>();
-        List<RegionInfo> regionList = groupToRegion.get(key);
+        List<RegionInfo> regionList = groupToRegion.get(group);
-        RSGroupInfo info = rsGroupInfoManager.getRSGroup(key);
+        RSGroupInfo info = rsGroupInfoManager.getRSGroup(group);
         List<ServerName> candidateList = filterOfflineServers(info, servers);
+        if (fallbackEnabled && candidateList.isEmpty()) {
+          candidateList = getFallBackCandidates(servers);
+        }
         for (RegionInfo region : regionList) {
           currentAssignmentMap.put(region, regions.get(region));
         }
@@ -213,7 +230,7 @@ public class RSGroupBasedLoadBalancer implements LoadBalancer {
             .putAll(this.internalBalancer.retainAssignment(currentAssignmentMap, candidateList));
         } else {
           if (LOG.isDebugEnabled()) {
-            LOG.debug("No available servers to assign regions: {}",
+            LOG.debug("No available servers for group {} to assign regions: {}", group,
                 RegionInfo.getShortNameToLog(regionList));
           }
           assignments.computeIfAbsent(LoadBalancer.BOGUS_SERVER_NAME, s -> new ArrayList<>())
@@ -250,7 +267,10 @@ public class RSGroupBasedLoadBalancer implements LoadBalancer {
       for (String groupKey : regionMap.keySet()) {
         RSGroupInfo info = rsGroupInfoManager.getRSGroup(groupKey);
         serverMap.putAll(groupKey, filterOfflineServers(info, servers));
-        if(serverMap.get(groupKey).size() < 1) {
+        if (fallbackEnabled && serverMap.get(groupKey).isEmpty()) {
+          serverMap.putAll(groupKey, getFallBackCandidates(servers));
+        }
+        if (serverMap.get(groupKey).isEmpty()) {
           serverMap.put(groupKey, LoadBalancer.BOGUS_SERVER_NAME);
         }
       }
@@ -369,6 +389,12 @@ public class RSGroupBasedLoadBalancer implements LoadBalancer {
       internalBalancer.setClusterMetrics(clusterStatus);
     }
     internalBalancer.initialize();
+    // init fallback groups
+    Collection<String> groups = config.getTrimmedStringCollection(FALLBACK_GROUPS_KEY);
+    if (groups != null && !groups.isEmpty()) {
+      this.fallbackEnabled = true;
+      this.fallbackGroups = new HashSet<>(groups);
+    }
   }
 
   public boolean isOnline() {
@@ -457,4 +483,17 @@ public class RSGroupBasedLoadBalancer implements LoadBalancer {
     }
     return regionPlans;
   }
+
+  private List<ServerName> getFallBackCandidates(List<ServerName> servers) {
+    List<ServerName> serverNames = new ArrayList<>();
+    for (String fallbackGroup : fallbackGroups) {
+      try {
+        RSGroupInfo info = rsGroupInfoManager.getRSGroup(fallbackGroup);
+        serverNames.addAll(filterOfflineServers(info, servers));
+      } catch (IOException e) {
+        LOG.error("Get group info for {} failed", fallbackGroup, e);
+      }
+    }
+    return serverNames;
+  }
 }

hbase-server/src/test/java/org/apache/hadoop/hbase/rsgroup/TestRSGroupsFallback.java

@@ -0,0 +1,128 @@
+/**
+ * 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.rsgroup;
+
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.util.Collections;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.client.ColumnFamilyDescriptorBuilder;
+import org.apache.hadoop.hbase.client.TableDescriptor;
+import org.apache.hadoop.hbase.client.TableDescriptorBuilder;
+import org.apache.hadoop.hbase.master.assignment.AssignmentTestingUtil;
+import org.apache.hadoop.hbase.net.Address;
+import org.apache.hadoop.hbase.testclassification.MediumTests;
+import org.apache.hadoop.hbase.testclassification.RSGroupTests;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.hbase.util.Threads;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+@Category({ RSGroupTests.class, MediumTests.class })
+public class TestRSGroupsFallback extends TestRSGroupsBase {
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+      HBaseClassTestRule.forClass(TestRSGroupsFallback.class);
+
+  protected static final Logger LOG = LoggerFactory.getLogger(TestRSGroupsFallback.class);
+
+  private static final String FALLBACK_GROUP = "fallback";
+
+  @BeforeClass
+  public static void setUp() throws Exception {
+    Configuration configuration = TEST_UTIL.getConfiguration();
+    configuration.set(RSGroupBasedLoadBalancer.FALLBACK_GROUPS_KEY, FALLBACK_GROUP);
+    setUpTestBeforeClass();
+    MASTER.balanceSwitch(true);
+  }
+
+  @AfterClass
+  public static void tearDown() throws Exception {
+    tearDownAfterClass();
+  }
+
+  @Before
+  public void beforeMethod() throws Exception {
+    setUpBeforeMethod();
+  }
+
+  @After
+  public void afterMethod() throws Exception {
+    tearDownAfterMethod();
+  }
+
+  @Test
+  public void testGroupFallback() throws Exception {
+    // add fallback group
+    addGroup(FALLBACK_GROUP, 1);
+    // add test group
+    String groupName = getGroupName(name.getMethodName());
+    addGroup(groupName, 1);
+    TableDescriptor desc = TableDescriptorBuilder.newBuilder(tableName)
+        .setColumnFamily(ColumnFamilyDescriptorBuilder.newBuilder(Bytes.toBytes("f")).build())
+        .setRegionServerGroup(groupName)
+        .build();
+    ADMIN.createTable(desc);
+    TEST_UTIL.waitUntilAllRegionsAssigned(tableName);
+    // server of test group crash
+    for (Address server : ADMIN.getRSGroup(groupName).getServers()) {
+      AssignmentTestingUtil.crashRs(TEST_UTIL, getServerName(server), true);
+    }
+    Threads.sleep(1000);
+    TEST_UTIL.waitUntilNoRegionsInTransition(10000);
+    TEST_UTIL.waitUntilAllRegionsAssigned(tableName);
+
+    // regions move to fallback group
+    assertRegionsInGroup(FALLBACK_GROUP);
+
+    // move a new server from default group
+    Address address = ADMIN.getRSGroup(RSGroupInfo.DEFAULT_GROUP).getServers().first();
+    ADMIN.moveServersToRSGroup(Collections.singleton(address), groupName);
+
+    // correct misplaced regions
+    MASTER.balance();
+
+    TEST_UTIL.waitUntilNoRegionsInTransition(10000);
+    TEST_UTIL.waitUntilAllRegionsAssigned(tableName);
+
+    // regions move back
+    assertRegionsInGroup(groupName);
+
+    TEST_UTIL.deleteTable(tableName);
+  }
+
+  private void assertRegionsInGroup(String group) throws IOException {
+    RSGroupInfo fallbackGroup = ADMIN.getRSGroup(group);
+    MASTER.getAssignmentManager().getRegionStates().getRegionsOfTable(tableName).forEach(region -> {
+      Address regionOnServer = MASTER.getAssignmentManager().getRegionStates()
+          .getRegionAssignments().get(region).getAddress();
+      assertTrue(fallbackGroup.getServers().contains(regionOnServer));
+    });
+  }
+}