@lesjoursfr/express-winston

winston middleware for express.js

Installation

npm install @lesjoursfr/express-winston

Usage

express-winston provides middlewares for request and error logging of your express.js application. It uses 'allowlists' 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": {
		"...": "...",
		"express": "^5.2.1",
		"winston": "^3.19.0",
		"...": "..."
	}
}

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

import winston from "winston";
import expressWinston from "@lesjoursfr/express-winston";

Request Logging

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

import router from "./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. Defaults to 'meta'. Set to `null` to store metadata at the root of the log entry.
    requestField: [String] // the property of the metadata to store the request under (default 'req'). Set to null to exclude request from metadata
    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 allowlist. 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 allowlist. If the function returns undefined, the key/value will not be included in the meta.
    requestAllowlist: [String], // Array of request properties to log. Overrides global requestAllowlist for this instance
    responseAllowlist: [String], // Array of response properties to log. Overrides global responseAllowlist for this instance
    bodyAllowlist: [String], // Array of body properties to log. Overrides global bodyAllowlist for this instance
    bodyDenylist: [String], // Array of body properties to omit from logs. Overrides global bodyDenylist 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
    headerDenylist: [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.

import router from "./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.
    meta: Boolean, // control whether you want to log the meta data about the request (default to true).
    metaField: String, // if defined, the meta data will be added in this field instead of the meta root object. Defaults to 'meta'. Set to `null` to store metadata at the root of the log entry.
    requestField: [String] // the property of the metadata to store the request under (default 'req'). Set to null to exclude request from metadata
    responseField: [String] // the property of the metadata to store the response under (default 'res'). If set to the same as 'requestField', filtered response and request properties will be merged. Set to null to exclude request from metadata
    requestFilter: function (req, propName) { return req[propName]; } // A function to filter/return request values, defaults to returning all values allowed by allowlist. If the function returns undefined, the key/value will not be included in the meta.
    requestAllowlist: [String] // Array of request properties to log. Overrides global requestAllowlist for this instance
    headerDenylist: [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
    denylistedMetaFields: [String] // fields to denylist 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.

metaField option

In versions of express-winston prior to 4.0.0, this field functioned differently.

Previously the log entry would always have a "meta" field which would be set to the metadata of the request/error. If metaField was set, this information would be stored as an object with the given property on the "meta" object of the log entry. This prevented the use case where the metadata should be located at the root of the log entry.

In this version, metaField defaults to "meta" which maintains the prior versions behavior of storing the metadata at a "meta" property of the log entry.

Explicitly setting the metaField to null or "null" causes the metadata to be stored at the root of the log entry.

The metaField option now also supports dot separated and array values to store the metadata at a nested location in the log entry.

Examples

import express from "express";
import expressWinston from "express-winston";
import winston from "winston"; // for transports.Console

const app = express();

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

// Let's make our express `Router` first.
const 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"
    }

StackDriver/Google Cloud Logging

If using this library with @google-cloud/logging-winston, use the following configuration to properly store httpRequest information.

See https://cloud.google.com/logging/docs/reference/v2/rest/v2/LogEntry

import express from "express";
import expressWinston from "express-winston";
import { LoggingWinston } from "@google-cloud/logging-winston";

const app = express();

app.use(
	expressWinston.logger({
		transports: [new LoggingWinston({})],
		metaField: null, //this causes the metadata to be stored at the root of the log entry
		responseField: null, // this prevents the response from being included in the metadata (including body and status code)
		requestAllowlist: ["headers", "query"], //these are not included in the standard StackDriver httpRequest
		responseAllowlist: ["body"], // this populates the `res.body` so we can get the response size (not required)
		dynamicMeta: (req, res) => {
			const httpRequest = {};
			const meta = {};
			if (req) {
				meta.httpRequest = httpRequest;
				httpRequest.requestMethod = req.method;
				httpRequest.requestUrl = `${req.protocol}://${req.get("host")}${req.originalUrl}`;
				httpRequest.protocol = `HTTP/${req.httpVersion}`;
				// httpRequest.remoteIp = req.ip // this includes both ipv6 and ipv4 addresses separated by ':'
				httpRequest.remoteIp =
					req.ip.indexOf(":") >= 0
						? req.ip.substring(req.ip.lastIndexOf(":") + 1)
						: req.ip; // just ipv4
				httpRequest.requestSize = req.socket.bytesRead;
				httpRequest.userAgent = req.get("User-Agent");
				httpRequest.referrer = req.get("Referrer");
			}

			if (res) {
				meta.httpRequest = httpRequest;
				httpRequest.status = res.statusCode;
				httpRequest.latency = {
					seconds: Math.floor(res.responseTime / 1000),
					nanos: (res.responseTime % 1000) * 1000000,
				};
				if (res.body) {
					if (typeof res.body === "object") {
						httpRequest.responseSize = JSON.stringify(
							res.body
						).length;
					} else if (typeof res.body === "string") {
						httpRequest.responseSize = res.body.length;
					}
				}
			}
			return meta;
		},
	})
);

Global Allowlists and Denylists

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

• requestAllowlist
• bodyAllowlist, bodyDenylist
• responseAllowlist

For example, requestAllowlist defaults to:

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

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

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

expressWinston.requestAllowlist.push("session");

The denylisting excludes certain properties and keeps all others. If both bodyAllowlist and bodyDenylist are set the properties excluded by the denylist are not included even if they are listed in the allowlist!

Example:

expressWinston.bodyDenylist.push("secretid", "secretproperty");

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

expressWinston.requestAllowlist.push("body");
expressWinston.responseAllowlist.push("body");

Nested Allowlists

requestAllowlist and responseAllowlist also support nested allowlist values, allowing access to parts of an object.

For example, using the following during logger setup:

expressWinston.responseAllowlist.push("body.important.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 Allowlists and Denylists

express-winston adds a _routeAllowlists object to the request, containing .body, .req and .res properties, to which you can set an array of 'allowlist' parameters to include in the log, specific to the route in question:

router.post("/user/register", function (req, res, next) {
	req._routeAllowlists.body = ["username", "email", "age"]; // But not 'password' or 'confirm-password' or 'top-secret'
	req._routeAllowlists.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": "[email protected]",
			"age": "72"
		}
	},
	"res": {
		"statusCode": 200
	},
	"responseTime": 12,
	"level": "info",
	"message": "HTTP GET /favicon.ico"
}

Denylisting supports only the body property.

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

If both req._routeAllowlists.body and req._routeDenylists.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 run test

Issues and Collaboration

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