1 /** 2 * Copyright 2010 The Apache Software Foundation 3 * 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, software 15 * distributed under the License is distributed on an "AS IS" BASIS, 16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 17 * See the License for the specific language governing permissions and 18 * limitations under the License. 19 */ 20 package org.apache.hadoop.hbase.master; 21 22 import org.apache.hadoop.hbase.HRegionInfo; 23 import org.apache.hadoop.hbase.RemoteExceptionHandler; 24 25 import java.io.IOException; 26 27 /** Scanner for the <code>ROOT</code> HRegion. */ 28 class RootScanner extends BaseScanner { 29 /** 30 * Constructor 31 * @param master 32 */ 33 public RootScanner(HMaster master) { 34 super(master, true, master.getShutdownRequested()); 35 } 36 37 /** 38 * Don't retry if we get an error while scanning. Errors are most often 39 * 40 * caused by the server going away. Wait until next rescan interval when 41 * things should be back to normal. 42 * @return True if successfully scanned. 43 */ 44 private boolean scanRoot() { 45 master.getRegionManager().waitForRootRegionLocation(); 46 if (master.isClosed()) { 47 return false; 48 } 49 50 try { 51 // Don't interrupt us while we're working 52 synchronized(scannerLock) { 53 if (master.getRegionManager().getRootRegionLocation() != null) { 54 scanRegion(new MetaRegion(master.getRegionManager().getRootRegionLocation(), 55 HRegionInfo.ROOT_REGIONINFO)); 56 } 57 } 58 } catch (IOException e) { 59 e = RemoteExceptionHandler.checkIOException(e); 60 LOG.warn("Scan ROOT region", e); 61 // Make sure the file system is still available 62 master.checkFileSystem(); 63 } catch (Exception e) { 64 // If for some reason we get some other kind of exception, 65 // at least log it rather than go out silently. 66 LOG.error("Unexpected exception", e); 67 } 68 return true; 69 } 70 71 @Override 72 protected boolean initialScan() { 73 this.initialScanComplete = scanRoot(); 74 return initialScanComplete; 75 } 76 77 @Override 78 protected void maintenanceScan() { 79 scanRoot(); 80 } 81 }