"dependencies": {
  "body-parser": "1.18.3",
  "compression": "1.7.2",
  "cookie-parser": "1.4.3",
  "ejs": "2.6.1",
  "express": "4.16.3",
  "forever": "0.15.3",
  "http-proxy-middleware": "0.18.0",
  "log4js": "2.9.0",
  "log4js-logstash-tcp": "1.0.1",
  "serve-favicon": "2.5.0"
 },

// filename: /logs/logger.js

var log4js = require('log4js')

// 获取配置文件中logstash的IP地址和端口
var {logHost, logPort} = require('../config/index.js') 

if (!logHost || !logPort) {
 console.log('ERROR not config logstash_host or logstash_port')
}

log4js.configure({
 appenders: {
  console: { type: 'console' },
  logstash: {
   // 因为我们的logstash暴露的是tcp写日志的端口，所以我用了log4js-logstash-tcp，
   // 这个需要安装 https://github.com/Aigent/log4js-logstash-tcp
   // 如果你的logstash使用UDP的，参考 https://github.com/log4js-node/logstashUDP
   type: 'log4js-logstash-tcp', 
   host: logHost,
   port: parseInt(logPort)
  }
 },
 categories: {
  default: { appenders: ['logstash'], level: 'debug' }
 }
})

const logger = log4js.getLogger('default')

// filename: /app.js
var express = require('express')
var compression = require('compression')
var path = require('path')
var log4js = require('log4js')
var proxyMiddleware = require('http-proxy-middleware')
var cookieParser = require('cookie-parser')

var logger = require('./logs/logger.js') // 这了引用了上面的logger
var {proxyTable, maxAge} = require('./config/index.js')

...
Object.keys(proxyTable).forEach(function (context) {
 if (!proxyTable[context].ws) {
  // 这里我是用的反向代理，当代理响应时，开始写日志
  proxyTable[context].onProxyRes = writeLog
 }
 app.use(proxyMiddleware(context, proxyTable[context]))
})
...

// 主要谢日日志的就是这里
function writeLog (proxyRes, req, res) {
 var baseLog = `${req.method} ${proxyRes.statusCode} ${req.cookies.email} ${req.url}`
 var msgObj = {
  method: req.method,
  statusCode: proxyRes.statusCode,
  url: req.url,
  email: req.cookies.email || '',
  sessionId: req.cookies.sessionId || '',
  instanceId: 'newTm',
  nodeName: 'newTm'
 }

 if (proxyRes.statusCode < 400) {
  logger.info(baseLog, msgObj)
 } else {
  logger.error(baseLog, msgObj)
 }
}

{
 "_index": "logstash-2018.07.11",
 "_type": "logs",
 "_id": "AWSIGyY0vR6RLdfU8xZj",
 "_score": null,
 "_source": {
  "nodeName": "newTm",
  "method": "GET",
  "level": "INFO",
  "sessionId": "",
  "message": "GET 204 test.cc.com /api/touch",
  "url": "/api/touch",
  "@timestamp": "2018-07-11T06:53:29.059Z",
  "port": 57250,
  "@version": "1",
  "host": "192.168.2.74",
  "fields": {
   "nodeName": "newTm",
   "method": "GET",
   "level": "INFO",
   "sessionId": "",
   "category": "default",
   "url": "/api/touch",
   "email": "test.cc.com",
   "statusCode": 204
  },
  "category": "default",
  "email": "test.cc.com",
  "statusCode": 204
 },
 "fields": {
  "@timestamp": [
   1531292009059
  ]
 },
 "highlight": {
  "nodeName": [
   "@kibana-highlighted-field@newTm@/kibana-highlighted-field@"
  ]
 },
 "sort": [
  1531292009059
 ]
}