log4js log access to logstash

log4config.js

var logger = log4js.getLogger('access');

app.use(function (req, res, next) {
  
  // 无法直接得到response.data信息
  res._json = res.json;
  res.json = function(data){
    res.responseData = data;
    res._json(data);
  };
  
  var start = new Date()
    , statusCode
    , writeHead = res.writeHead
    , url = req.originalUrl;

  res.writeHead = function(code, headers){
    res.writeHead = writeHead;
    res.writeHead(code, headers);
    res.__statusCode = statusCode = code;
    res.__headers = headers || {};
  };

  res.on('finish', function() {
    res.responseTime = new Date() - start;
    var log = {
      host: require('os').hostname(),
      category: 'access',
      method: req.method,
      url: req.originalUrl,
      responseTime: res.responseTime + ' ms',
      status: res.__statusCode || res.statusCode,
      remoteAddress: req.ip || req._remoteAddress || ( req.socket && (req.socket.remoteAddress || (req.socket.socket && req.socket.socket.remoteAddress))) || 'unknown',
      body: req.body || {},
      ua: req.headers["user-agent"] || '',
      webappVersion: req.headers["X-Webapp-Version"] || '',
      referrer: req.headers.referer || req.headers.referrer || '',
      apiVersion: req.headers["accept-version"] || 'v1',
    }
    if(res.statusCode >= 400){
      log.responseData = res.responseData;
    }
    logger.info(JSON.stringify(log));
  });
  next();
})