express-winston

What is express-winston?

express-winston is a middleware for logging HTTP requests and responses in Express applications. It integrates with the winston logging library, allowing you to log requests and responses in a structured and customizable way.

What are express-winston's main functionalities?

Request Logging

This feature allows you to log incoming HTTP requests. The code sample demonstrates how to set up express-winston to log requests to the console with a specific format.

const express = require('express');
const winston = require('winston');
const expressWinston = require('express-winston');

const app = express();

app.use(expressWinston.logger({
  transports: [
    new winston.transports.Console()
  ],
  format: winston.format.combine(
    winston.format.colorize(),
    winston.format.json()
  ),
  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.
  expressFormat: true, // Use the default Express/morgan request formatting
  colorize: false, // Color the text and status code, using the Express/morgan color palette
  ignoreRoute: function (req, res) { return false; } // optional: allows to skip some log messages based on request and/or response
}));

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Error Logging

This feature allows you to log errors that occur during the handling of requests. The code sample demonstrates how to set up express-winston to log errors to the console.

const express = require('express');
const winston = require('winston');
const expressWinston = require('express-winston');

const app = express();

app.use(expressWinston.errorLogger({
  transports: [
    new winston.transports.Console()
  ],
  format: winston.format.combine(
    winston.format.colorize(),
    winston.format.json()
  )
}));

app.get('/', (req, res) => {
  throw new Error('Something went wrong!');
});

app.use((err, req, res, next) => {
  res.status(500).send('Internal Server Error');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Custom Transports

This feature allows you to use custom transports for logging. The code sample demonstrates how to set up express-winston to log requests to a file.

const express = require('express');
const winston = require('winston');
const expressWinston = require('express-winston');
const fs = require('fs');

const app = express();

const fileTransport = new winston.transports.File({ filename: 'logfile.log' });

app.use(expressWinston.logger({
  transports: [
    fileTransport
  ],
  format: winston.format.combine(
    winston.format.timestamp(),
    winston.format.json()
  )
}));

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Other packages similar to express-winston

morgan

Morgan is another HTTP request logger middleware for Node.js. It is simpler and more lightweight compared to express-winston, but it does not offer the same level of customization and integration with winston.

bunyan

Bunyan is a simple and fast JSON logging library for Node.js services. It provides a similar functionality to express-winston but uses its own logging system instead of winston.

pino

Pino is a fast and low-overhead logging library for Node.js. It offers high performance and can be used with express-pino-logger for request logging, similar to express-winston.

README

express-winston

winston middleware for express.js

Changelog

CALL FOR MAINTAINERS

Installation

npm install winston express-winston

(supports node >= 6)

Usage

express-winston provides middlewares for request and error logging of your express.js application. It uses 'whitelists' to select properties from the request and (new in 0.2.x) response objects.

To make use of express-winston, you need to add the following to your application:

In package.json:

{
  "dependencies": {
    "...": "...",
    "winston": "^3.0.0",
    "express-winston": "^3.0.0",
    "...": "..."
  }
}

In server.js (or wherever you need it):

var winston = require('winston'),
    expressWinston = require('express-winston');

Request Logging

Use expressWinston.logger(options) to create a middleware to log your HTTP requests.

    var router = require('./my-express-router');

    app.use(expressWinston.logger({
      transports: [
        new winston.transports.Console()
      ],
      format: winston.format.combine(
        winston.format.colorize(),
        winston.format.json()
      ),
      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) { return false; } // optional: allows to skip some log messages based on request and/or response
    }));

    app.use(router); // notice how the router goes after the logger.

Options

    transports: [<WinstonTransport>], // list of all winston transports instances to use.
    format: [<logform.Format>], // formatting desired for log output.
    winstonInstance: <WinstonLogger>, // a winston logger instance. If this is provided the transports and formats options are ignored.
    level: String or function(req, res) { return String; }, // log level to use, the default is "info". Assign a  function to dynamically set the level based on request and response, or a string to statically set it always at that level. statusLevels must be false for this setting to be used.
    msg: String or function, // customize the default logging message. E.g. "{{res.statusCode}} {{req.method}} {{res.responseTime}}ms {{req.url}}", "HTTP {{req.method}} {{req.url}}" or function(req, res) { return `${res.statusCode} - ${req.method}`.  Warning: while supported, returning mustache style interpolation from an options.msg function has performance and memory implications under load.
    expressFormat: Boolean, // Use the default Express/morgan request formatting. Enabling this will override any msg if true. Will only output colors when colorize set to true
    colorize: Boolean, // Color the text and status code, using the Express/morgan color palette (text: gray, status: default green, 3XX cyan, 4XX yellow, 5XX red).
    meta: Boolean, // control whether you want to log the meta data about the request (default to true).
    baseMeta: Object, // default meta data to be added to log, this will be merged with the meta data.
    metaField: String, // if defined, the meta data will be added in this field instead of the meta root object.
    statusLevels: Boolean or Object, // different HTTP status codes caused log messages to be logged at different levels (info/warn/error), the default is false. Use an object to control the levels various status codes are logged at. Using an object for statusLevels overrides any setting of options.level.
    ignoreRoute: function (req, res) { return false; }, // A function to determine if logging is skipped, defaults to returning false. Called _before_ any later middleware.
    skip: function(req, res) { return false; }, // A function to determine if logging is skipped, defaults to returning false. Called _after_ response has already been sent.
    requestFilter: function (req, propName) { return req[propName]; }, // A function to filter/return request values, defaults to returning all values allowed by whitelist. If the function returns undefined, the key/value will not be included in the meta.
    responseFilter: function (res, propName) { return res[propName]; }, // A function to filter/return response values, defaults to returning all values allowed by whitelist. If the function returns undefined, the key/value will not be included in the meta.
    requestWhitelist: [String], // Array of request properties to log. Overrides global requestWhitelist for this instance
    responseWhitelist: [String], // Array of response properties to log. Overrides global responseWhitelist for this instance
    bodyWhitelist: [String], // Array of body properties to log. Overrides global bodyWhitelist for this instance
    bodyBlacklist: [String], // Array of body properties to omit from logs. Overrides global bodyBlacklist for this instance
    ignoredRoutes: [String], // Array of paths to ignore/skip logging. Overrides global ignoredRoutes for this instance
    dynamicMeta: function(req, res) { return [Object]; } // Extract additional meta data from request or response (typically req.user data if using passport). meta must be true for this function to be activated
    headerBlacklist: [String], // Array of headers to omit from logs. Applied after any previous filters.

Error Logging

Use expressWinston.errorLogger(options) to create a middleware that log the errors of the pipeline.

    var router = require('./my-express-router');

    app.use(router); // notice how the router goes first.
    app.use(expressWinston.errorLogger({
      transports: [
        new winston.transports.Console()
      ],
      format: winston.format.combine(
        winston.format.colorize(),
        winston.format.json()
      )
    }));

The logger needs to be added AFTER the express router(app.router)) and BEFORE any of your custom error handlers(express.handler). Since express-winston will just log the errors and not handle them, you can still use your custom error handler like express.handler, just be sure to put the logger before any of your handlers.

Options

    transports: [<WinstonTransport>], // list of all winston transports instances to use.
    format: [<logform.Format>], // formatting desired for log output
    winstonInstance: <WinstonLogger>, // a winston logger instance. If this is provided the transports and formats options are ignored.
    msg: String or function // customize the default logging message. E.g. "{{err.message}} {{res.statusCode}} {{req.method}}" or function(req, res) { return `${res.statusCode} - ${req.method}` }
    baseMeta: Object, // default meta data to be added to log, this will be merged with the error data.
    metaField: String, // if defined, the meta data will be added in this field instead of the meta root object.
    requestFilter: function (req, propName) { return req[propName]; } // A function to filter/return request values, defaults to returning all values allowed by whitelist. If the function returns undefined, the key/value will not be included in the meta.
    requestWhitelist: [String] // Array of request properties to log. Overrides global requestWhitelist for this instance
    headerBlacklist: [String], // Array of headers to omit from logs. Applied after any previous filters.
    level: String or function(req, res, err) { return String; }// custom log level for errors (default is 'error'). Assign a function to dynamically set the log level based on request, response, and the exact error.
    dynamicMeta: function(req, res, err) { return [Object]; } // Extract additional meta data from request or response (typically req.user data if using passport). meta must be true for this function to be activated
    exceptionToMeta: function(error){return Object; } // Function to format the returned meta information on error log. If not given `winston.exception.getAllInfo` will be used by default
    blacklistedMetaFields: [String] // fields to blacklist from meta data
    skip: function(req, res, err) { return false; } // A function to determine if logging is skipped, defaults to returning false.

To use winston's existing transports, set transports to the values (as in key-value) of the winston.default.transports object. This may be done, for example, by using underscorejs: transports: _.values(winston.default.transports).

Alternatively, if you're using a winston logger instance elsewhere and have already set up levels and transports, pass the instance into expressWinston with the winstonInstance option. The transports option is then ignored.

Examples

    var express = require('express');
    var expressWinston = require('express-winston');
    var winston = require('winston'); // for transports.Console
    var app = module.exports = express();

    app.use(express.bodyParser());
    app.use(express.methodOverride());

    // Let's make our express `Router` first.
    var router = express.Router();
    router.get('/error', function(req, res, next) {
      // here we cause an error in the pipeline so we see express-winston in action.
      return next(new Error("This is an error and it should be logged to the console"));
    });

    router.get('/', function(req, res, next) {
      res.write('This is a normal request, it should be logged to the console too');
      res.end();
    });

    // express-winston logger makes sense BEFORE the router
    app.use(expressWinston.logger({
      transports: [
        new winston.transports.Console()
      ],
      format: winston.format.combine(
        winston.format.colorize(),
        winston.format.json()
      )
    }));

    // Now we can tell the app to use our routing code:
    app.use(router);

    // express-winston errorLogger makes sense AFTER the router.
    app.use(expressWinston.errorLogger({
      transports: [
        new winston.transports.Console()
      ],
      format: winston.format.combine(
        winston.format.colorize(),
        winston.format.json()
      )
    }));

    // Optionally you can include your custom error handler after the logging.
    app.use(express.errorLogger({
      dumpExceptions: true,
      showStack: true
    }));

    app.listen(3000, function(){
      console.log("express-winston demo listening on port %d in %s mode", this.address().port, app.settings.env);
    });

Browse / to see a regular HTTP logging like this:

{
  "req": {
    "httpVersion": "1.1",
    "headers": {
      "host": "localhost:3000",
      "connection": "keep-alive",
      "accept": "*/*",
      "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_4) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.57 Safari/536.11",
      "accept-encoding": "gzip,deflate,sdch",
      "accept-language": "en-US,en;q=0.8,es-419;q=0.6,es;q=0.4",
      "accept-charset": "ISO-8859-1,utf-8;q=0.7,*;q=0.3",
      "cookie": "connect.sid=nGspCCSzH1qxwNTWYAoexI23.seE%2B6Whmcwd"
    },
    "url": "/",
    "method": "GET",
    "originalUrl": "/",
    "query": {}
  },
  "res": {
    "statusCode": 200
  },
  "responseTime" : 12,
  "level": "info",
  "message": "HTTP GET /favicon.ico"
}

Browse /error will show you how express-winston handles and logs the errors in the express pipeline like this:

{
  "date": "Thu Jul 19 2012 23:39:44 GMT-0500 (COT)",
  "process": {
    "pid": 35719,
    "uid": 501,
    "gid": 20,
    "cwd": "/Users/thepumpkin/Projects/testExpressWinston",
    "execPath": "/usr/local/bin/node",
    "version": "v0.6.18",
    "argv": [
      "node",
      "/Users/thepumpkin/Projects/testExpressWinston/app.js"
    ],
    "memoryUsage": {
      "rss": 14749696,
      "heapTotal": 7033664,
      "heapUsed": 5213280
    }
  },
  "os": {
    "loadavg": [
      1.95068359375,
      1.5166015625,
      1.38671875
    ],
    "uptime": 498086
  },
  "trace": [
    ...,
    {
      "column": 3,
      "file": "Object].log (/Users/thepumpkin/Projects/testExpressWinston/node_modules/winston/lib/winston/transports/console.js",
      "function": "[object",
      "line": 87,
      "method": null,
      "native": false
    }
  ],
  "stack": [
    "Error: This is an error and it should be logged to the console",
    "    at /Users/thepumpkin/Projects/testExpressWinston/app.js:39:15",
    "    at callbacks (/Users/thepumpkin/Projects/testExpressWinston/node_modules/express/lib/router/index.js:272:11)",
    "    at param (/Users/thepumpkin/Projects/testExpressWinston/node_modules/express/lib/router/index.js:246:11)",
    "    at pass (/Users/thepumpkin/Projects/testExpressWinston/node_modules/express/lib/router/index.js:253:5)",
    "    at Router._dispatch (/Users/thepumpkin/Projects/testExpressWinston/node_modules/express/lib/router/index.js:280:4)",
    "    at Object.handle (/Users/thepumpkin/Projects/testExpressWinston/node_modules/express/lib/router/index.js:45:10)",
    "    at next (/Users/thepumpkin/Projects/testExpressWinston/node_modules/express/node_modules/connect/lib/http.js:204:15)",
    "    at done (/Users/thepumpkin/Dropbox/Projects/express-winston/index.js:91:14)",
    "    at /Users/thepumpkin/Dropbox/Projects/express-winston/node_modules/async/lib/async.js:94:25",
    "    at [object Object].log (/Users/thepumpkin/Projects/testExpressWinston/node_modules/winston/lib/winston/transports/console.js:87:3)"
  ],
  "req": {
    "httpVersion": "1.1",
    "headers": {
      "host": "localhost:3000",
      "connection": "keep-alive",
      "cache-control": "max-age=0",
      "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_4) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.57 Safari/536.11",
      "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
      "accept-encoding": "gzip,deflate,sdch",
      "accept-language": "en-US,en;q=0.8,es-419;q=0.6,es;q=0.4",
      "accept-charset": "ISO-8859-1,utf-8;q=0.7,*;q=0.3",
      "cookie": "connect.sid=nGspCCSzH1qxwNTWYAoexI23.seE%2B6WhmcwdzFEjqhMDuIIl3mAUY7dT4vn%2BkWvRPhZc"
    },
    "url": "/error",
    "method": "GET",
    "originalUrl": "/error",
    "query": {}
  },
  "level": "error",
  "message": "middlewareError"
}

Global Whitelists and Blacklists

Express-winston exposes three whitelists that control which properties of the request, body, and response are logged:

• requestWhitelist
• bodyWhitelist, bodyBlacklist
• responseWhitelist

For example, requestWhitelist defaults to:

['url', 'headers', 'method', 'httpVersion', 'originalUrl', 'query'];

Only those properties of the request object will be logged. Set or modify the whitelist as necessary.

For example, to include the session property (the session data), add the following during logger setup:

expressWinston.requestWhitelist.push('session');

The blacklisting excludes certain properties and keeps all others. If both bodyWhitelist and bodyBlacklist are set the properties excluded by the blacklist are not included even if they are listed in the whitelist!

Example:

expressWinston.bodyBlacklist.push('secretid', 'secretproperty');

Note that you can log the whole request and/or response body:

expressWinston.requestWhitelist.push('body');
expressWinston.responseWhitelist.push('body');

Nested Whitelists

requestWhitelist and responseWhitelist also support nested whitelist values, allowing access to parts of an object.

For example, using the following during logger setup:

expressWinston.responseWhitelist.push('body.import.value');

A response that looks like this :

{
    body: {
        important: {
            value: 5
        },
        notImportant: {
            value: 7
        }
    },
    other: {
        value: 3
    }
}

Would only log the following value :

{
    body: {
        important: {
            value: 5
        }
    }
}

Route-Specific Whitelists and Blacklists

New in version 0.2.x is the ability to add whitelist elements in a route. express-winston adds a _routeWhitelists object to the request, containing .body, .req and .res` properties, to which you can set an array of 'whitelist' parameters to include in the log, specific to the route in question:

    router.post('/user/register', function(req, res, next) {
      req._routeWhitelists.body = ['username', 'email', 'age']; // But not 'password' or 'confirm-password' or 'top-secret'
      req._routeWhitelists.res = ['_headers'];
    });

Post to /user/register would give you something like the following:

{
  "req": {
    "httpVersion": "1.1",
    "headers": {
      "host": "localhost:3000",
      "connection": "keep-alive",
      "accept": "*/*",
      "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_4) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.57 Safari/536.11",
      "accept-encoding": "gzip,deflate,sdch",
      "accept-language": "en-US,en;q=0.8,es-419;q=0.6,es;q=0.4",
      "accept-charset": "ISO-8859-1,utf-8;q=0.7,*;q=0.3",
      "cookie": "connect.sid=nGspCCSzH1qxwNTWYAoexI23.seE%2B6Whmcwd"
    },
    "url": "/",
    "method": "GET",
    "originalUrl": "/",
    "query": {},
    "body": {
      "username": "foo",
      "email": "[e-mail]",
      "age": "72"
    }
  },
  "res": {
    "statusCode": 200
  },
  "responseTime" : 12,
  "level": "info",
  "message": "HTTP GET /favicon.ico"
}

Blacklisting supports only the body property.

    router.post('/user/register', function(req, res, next) {
      req._routeWhitelists.body = ['username', 'email', 'age']; // But not 'password' or 'confirm-password' or 'top-secret'
      req._routeBlacklists.body = ['username', 'password', 'confirm-password', 'top-secret'];
      req._routeWhitelists.res = ['_headers'];
    });

If both req._routeWhitelists.body and req._routeBlacklists.body are set the result will be the white listed properties excluding any black listed ones. In the above example, only 'email' and 'age' would be included.

Custom Status Levels

If you set statusLevels to true express-winston will log sub 400 responses at info level, sub 500 responses as warnings and 500+ responses as errors. To change these levels specify an object as follows

  "statusLevels": {
    "success": "debug",
    "warn": "debug",
    "error": "info"
  }

Dynamic Status Levels

If you set statusLevels to false and assign a function to level, you can customize the log level for any scenario.

  statusLevels: false // default value
  level: function (req, res) {
    var level = "";
    if (res.statusCode >= 100) { level = "info"; }
    if (res.statusCode >= 400) { level = "warn"; }
    if (res.statusCode >= 500) { level = "error"; }
    // Ops is worried about hacking attempts so make Unauthorized and Forbidden critical
    if (res.statusCode == 401 || res.statusCode == 403) { level = "critical"; }
    // No one should be using the old path, so always warn for those
    if (req.path === "/v1" && level === "info") { level = "warn"; }
    return level;
  }

Dynamic meta data from request or response

If you set dynamicMeta function you can extract additional meta data fields from request or response objects. The function can be used to either select relevant elements in request or response body without logging them as a whole or to extract runtime data like the user making the request. The example below logs the user name and role as assigned by the passport authentication middleware.

   meta: true,
   dynamicMeta: function(req, res) {
     return {
       user: req.user ? req.user.username : null,
       role: req.user ? req.user.role : null,
       ...
   }
}

Tests

Run the basic Mocha tests:

npm test

View the coverage report:

npx http-server coverage/lcov-report

Issues and Collaboration

If you ran into any problems, please use the project Issues section to search or post any bug.

Contributors

• Johan Hernandez (https://github.com/bithavoc)
• Lars Jacob (https://github.com/jaclar)
• Jonathan Lomas (https://github.com/floatingLomas)
• Ross Brandes (https://github.com/rosston)
• Alex Kaplan (https://github.com/kapalex)

Also see AUTHORS file, add yourself if you are missing.

MIT License

Copyright (c) 2012 Bithavoc.io and Contributors - http://bithavoc.io

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Changelog

3.4.0

• Added: Nested Whitelists (#225, @kapalex)