org.apache.hadoop.hbase.zookeeper.ZKUtil#listChildrenAndWatchThem ( )源码实例Demo

/**
 * Starts the tracking of draining RegionServers.
 *
 * <p>All Draining RSs will be tracked after this method is called.
 *
 * @throws KeeperException
 */
public void start() throws KeeperException, IOException {
  watcher.registerListener(this);
  // Add a ServerListener to check if a server is draining when it's added.
  serverManager.registerListener(new ServerListener() {
    @Override
    public void serverAdded(ServerName sn) {
      if (drainingServers.contains(sn)){
        serverManager.addServerToDrainList(sn);
      }
    }
  });
  List<String> servers =
    ZKUtil.listChildrenAndWatchThem(watcher, watcher.getZNodePaths().drainingZNode);
  add(servers);
}
 

/**
 * Read the list of children under the archive znode as table names and then sets those tables to
 * the list of tables that we should archive
 * @throws KeeperException if there is an unexpected zk exception
 */
private void updateWatchedTables() throws KeeperException {
  // get the children and watch for new children
  LOG.debug("Updating watches on tables to archive.");
  // get the children and add watches for each of the children
  List<String> tables = ZKUtil.listChildrenAndWatchThem(watcher, archiveHFileZNode);
  LOG.debug("Starting archive for tables:" + tables);
  // if archiving is still enabled
  if (tables != null && tables.size() > 0) {
    getMonitor().setArchiveTables(tables);
  } else {
    LOG.debug("No tables to archive.");
    // only if we currently have a tracker, then clear the archive
    clearTables();
  }
}
 

/**
 * Get a list of all the other region servers in this cluster and set a watch
 * @return a list of server nanes
 */
private List<String> getRegisteredRegionServers(boolean watch) {
  List<String> result = null;
  try {
    if (watch) {
      result = ZKUtil.listChildrenAndWatchThem(this.zookeeper,
              this.zookeeper.getZNodePaths().rsZNode);
    } else {
      result = ZKUtil.listChildrenNoWatch(this.zookeeper, this.zookeeper.getZNodePaths().rsZNode);
    }
  } catch (KeeperException e) {
    this.abortable.abort("Get list of registered region servers", e);
  }
  return result;
}