HBASE-27793 Make HBCK be able to report unknown servers

hbase-server/src/main/java/org/apache/hadoop/hbase/util/HBaseFsck.java

@@ -655,6 +655,8 @@ public int onlineConsistencyRepair() throws IOException, KeeperException, Interr
     loadDeployedRegions();
     // check whether hbase:meta is deployed and online
     recordMetaRegion();
+    // Report inconsistencies if there are any unknown servers.
+    reportUnknownServers();
     // Check if hbase:meta is found only once and in the right place
     if (!checkMetaRegion()) {
       String errorMsg = "hbase:meta table is not consistent. ";
@@ -707,6 +709,18 @@ public int onlineConsistencyRepair() throws IOException, KeeperException, Interr
     return errors.getErrorList().size();
   }
 
+  private void reportUnknownServers() throws IOException {
+    List<ServerName> unknownServers = admin.listUnknownServers();
+    if (!unknownServers.isEmpty()) {
+      unknownServers.stream().forEach(serverName -> {
+        errors.reportError(ERROR_CODE.UNKNOWN_SERVER,
+          "Found unknown server,"
+            + "some of the regions held by this server may not get assigned. "
+            + String.format("Use HBCK2 scheduleRecoveries %s to recover.", serverName));
+      });
+    }
+  }
+
   /**
    * This method maintains an ephemeral znode. If the creation fails we return false or throw
    * exception

hbase-server/src/main/java/org/apache/hadoop/hbase/util/HbckErrorReporter.java

@@ -65,7 +65,8 @@ enum ERROR_CODE {
     UNDELETED_REPLICATION_QUEUE,
     DUPE_ENDKEYS,
     UNSUPPORTED_OPTION,
-    INVALID_TABLE
+    INVALID_TABLE,
+    UNKNOWN_SERVER
   }
 
   void clear();

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

@@ -40,6 +40,9 @@
 import org.apache.hadoop.hbase.TableExistsException;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.TableNotFoundException;
+import org.apache.hadoop.hbase.master.HMaster;
+import org.apache.hadoop.hbase.master.assignment.AssignmentManager;
+import org.apache.hadoop.hbase.master.assignment.RegionStateNode;
 import org.apache.hadoop.hbase.regionserver.storefiletracker.StoreFileTrackerFactory;
 import org.apache.hadoop.hbase.testclassification.ClientTests;
 import org.apache.hadoop.hbase.testclassification.LargeTests;
@@ -552,4 +555,23 @@ public void testOnlineChangeTableSchema() throws IOException, InterruptedExcepti
     ADMIN.listTableDescriptors();
     assertFalse(ADMIN.tableExists(tableName));
   }
+
+  @Test
+  public void testUnknownServers() throws Exception {
+    TableName table = TableName.valueOf(name.getMethodName());
+    ColumnFamilyDescriptor cfd = ColumnFamilyDescriptorBuilder.of(HConstants.CATALOG_FAMILY);
+    ADMIN.createTable(TableDescriptorBuilder.newBuilder(table).setColumnFamily(cfd).build());
+    final List<RegionInfo> regions = ADMIN.getRegions(table);
+    HMaster master = TEST_UTIL.getHBaseCluster().getMaster();
+    final AssignmentManager am = master.getAssignmentManager();
+    RegionStateNode rsNode = am.getRegionStates().getRegionStateNode(regions.get(0));
+    ServerName regionLocation = rsNode.getRegionLocation();
+    rsNode.setRegionLocation(ServerName.valueOf("dummyserver", 1234, System.currentTimeMillis()));
+    try {
+      assertTrue(ADMIN.listUnknownServers().get(0).getHostname().equals("dummyserver"));
+    } finally {
+      rsNode.setRegionLocation(regionLocation);
+    }
+    assertTrue(ADMIN.listUnknownServers().isEmpty());
+  }
 }