docs: private void emitLogHeader(Context context, String mapredTaskId) throws IOException, InterruptedException {
      Configuration conf = context.getConfiguration();
      Text textId = new Text(mapredTaskId);
  
      for (Map.Entry<String, String> entry: conf) {
        StringBuilder sb = new StringBuilder();
        sb.append(entry.getKey());
        sb.append("=");
        sb.append(entry.getValue());
        context.write(textId, new Text(sb.toString()));
      }
  
      context.write(textId, new Text("----- Properties -----"));
      String[] plist = {
              "mapred.local.dir",
              "mapred.child.java.opts",
      };
      for (String k : plist) {
        String v = conf.get(k);
        if (v == null) {
          v = "(null)";
        }
        context.write(textId, new Text(k + " " + v));
      }
      String userDir = System.getProperty("user.dir");
      context.write(textId, new Text("user.dir " + userDir));
  
      try {
        java.net.InetAddress localMachine = java.net.InetAddress.getLocalHost();
        context.write(textId, new Text("hostname " + localMachine.getHostName()));
      }
      catch (java.net.UnknownHostException uhe) {
        // handle exception
      }
    }