Summary of how to use nodejs log module winston

This time I will bring you a summary of how to use the nodejs log module winston. What are the precautions when using the nodejs log module winston? The following is a practical case, let's take a look.

winston log module

In using the nodejs winston module, adding the two related modules will get twice the result with half the effort.

1. express-winston

2. winston-daily-rotate-file

express -winston

is an increased version of express-winston's winston. It is used as express's middleware to print logs. It not only has request header information, but also has response time.
As middleware, why is there a response time? Because express-winston rewrites express's res.end method, the log is generated after the request is completed.

Code snippet

var end = res.end;
res.end = function(chunk, encoding) {
 res.responseTime = (new Date) - req._startTime;
 res.end = end;
 res.end(chunk, encoding);
 ...
 }

express-winston does not modify or extend winston's transport, and winston-daily-rotate-file just enhances winston's transport method

winston-daily-rotate-file

winston-daily-rotate-file is an extension of winston, which adds a transport method so that winston has the ability to roll logs.

Combined use

We have a requirement: How to make express-winston print the log, and also print out the request parameters of the interface/api and response data?

1. The log middleware should be behind the call chain api and before api/* business processing. like: app.use('/api', apiRequestLogger, apiHandler)

2. To get the response data, it can only be captured after the business is processed and sent out. All express The final request response is res.send. We can start from here to capture the response data

The code is as follows

import winston from 'winston'
import expressWinston from 'express-winston'
import 'winston-daily-rotate-file'
import path from 'path'
export let DailyRotateFileTransport = (fileName) => {
 return new (winston.transports.DailyRotateFile)({
 filename: path.join(process.env.LOGPATH, `${fileName}-%DATE%.log`),
 datePattern: 'YYYY-MM-DD-HH',
 // maxSize: '20m',
 maxFiles: '7d',
 timestamp: () => new Date().format('yyyy-MM-dd hh:mm:ss.S')
 })
}
export let pageRequestLogger = expressWinston.logger({
 transports: [
 DailyRotateFileTransport('page-request')
 ],
 meta: true, // optional: control whether you want to log the meta data about the request (default to true)
 msg: 'HTTP {{req.method}} {{req.url}}', // optional: customize the default logging message. E.g. "{{res.statusCode}} {{req.method}} {{res.responseTime}}ms {{req.url}}"
 expressFormat: true, // Use the default Express/morgan request formatting. Enabling this will override any msg if true. Will only output colors with colorize set to true
 colorize: false, // Color the text and status code, using the Express/morgan color palette (text: gray, status: default green, 3XX cyan, 4XX yellow, 5XX red).
 ignoreRoute: function (req, res) {
 // 只打印页面请求信息
 let notPageRequest = false
 let ignoreArr = ['/api', '.js', '.css', '.png', '.jpg', '.gif']
 ignoreArr.forEach(item => {
  if (req.url.indexOf(item) > -1) notPageRequest = true
 })
 return notPageRequest
 } // optional: allows to skip some log messages based on request and/or response
})
export let apiRequestLogger = (req, res, next) => {
 let send = res.send
 let content = ''
 let query = req.query || {}
 let body = req.body || {}
 res.send = function () {
 content = arguments[0]
 send.apply(res, arguments)
 }
 expressWinston.logger({
 transports: [
  DailyRotateFileTransport('api-request')
 ],
 meta: true, // optional: control whether you want to log the meta data about the request (default to true)
 msg () {
  return `HTTP ${req.method} ${req.url} query ${JSON.stringify(query)} body ${JSON.stringify(body)} resData ${content} `
 },
 colorize: true, // Color the text and status code, using the Express/morgan color palette (text: gray, status: default green, 3XX cyan, 4XX yellow, 5XX red).
 ignoreRoute: function (req, res) {
  if (req.headers.self) return true
  return false
 } // optional: allows to skip some log messages based on request and/or response
 })(req, res, next)
}

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