import org.apache.hadoop.ha.NodeFencer; //导入依赖的package包/类
public JobTrackerHAServiceTarget(Configuration conf, String jtId) {
  this.logicalName = HAUtil.getLogicalName(conf);
  this.jtId = jtId;

  // Make a copy of the conf, and override configs based on the
  // target node -- not the node we happen to be running on.
  JobConf targetConf = new JobConf(conf);
  HAUtil.setGenericConf(targetConf, logicalName, jtId, HAUtil.JOB_TRACKER_SPECIFIC_KEYS);
  
  this.addr = HAUtil.getJtHaRpcAddress(targetConf, jtId);

  this.autoFailoverEnabled = targetConf.getBoolean(
      HAUtil.MR_HA_AUTO_FAILOVER_ENABLED_KEY,
      HAUtil.MR_HA_AUTO_FAILOVER_ENABLED_DEFAULT);
  if (autoFailoverEnabled) {
    int port = MRZKFailoverController.getZkfcPort(targetConf);
    if (port != 0) {
      setZkfcPort(port);
    }
  }
  try {
    fencer = NodeFencer.create(targetConf, HAUtil.MR_HA_FENCING_METHODS_KEY);
  } catch (BadFencingConfigurationException e) {
    this.fenceConfigError = e;
  }
}
 

import org.apache.hadoop.ha.NodeFencer; //导入依赖的package包/类
@Override
public NodeFencer getFencer() {
  return null;
}
 

import org.apache.hadoop.ha.NodeFencer; //导入依赖的package包/类
@Override
public NodeFencer getFencer() {
  return fencer;
}