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a bunyan logger middleware for express


A express logger middleware powered by bunyan.

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npm install express-bunyan-logger

To use the logger:


To use the errorLogger:


And you can also pass bunyan logger options to the logger middleware:

    name: 'logger',
    streams: [{
        level: 'info',
        stream: process.stdout

Change default format:

    format: ":remote-address - :user-agent[major] custom logger"

And a child logger will be attached to each request object:

app.use(function(req, res, next) {
    req.log.debug('this is debug in middleware');

Format string, please go the source code to the metadata. ":name" will print out; ":name[key]" will print out the property 'key' of

Or you can pass a function to options.format. This function accept a object as argument and return string.

Whether to parse user-agent in logger, default is =true=.

Function that translate statusCode into log level. The meta argument is an object consisting of all the fields gathered by bunyan-express-logger, before exclusions are applied.

function(status, err /* only will work in error logger */, meta) {
     // return string of level
     if (meta["response-time"] > 30000) {
         return "fatal";
     } else {
         return "info";

Function that is passed req and res, and returns an object whose properties will be added to the meta object passed to bunyan

function(req, res) {
    if (req.user) {
        return {
            _id: req.user._id,

Array of string, Those fields will be excluded from meta object which passed to bunyan

Array of strings to obfuscate. These strings can be in dotted notation, for instance body.password, and it will only replace that specific value. This will replace the values in log messages with a placeholder.

Placeholder to use when obfuscating values. This is only applicable when there are values to obfuscate. Default is [HIDDEN].

An object of bunyan serializers. They are passed on to bunyan. The default serializers are defined as follows:

    req: bunyan.stdSerializers.req,
    res: bunyan.stdSerializers.res,
    err: bunyan.stdSerializers.err

Write log line on request instead of response (for response times)

By default, express-bunyan-logger will generate an unique id for each request, and a field 'req_id' will be added to child logger in request object.

If you have already use other middleware/framework to generate request id, you can pass a function to retrieve it:

// suppose connect-requestid middleware is already added. 
    genReqId: function(req) {

(The BSD License)

Copyright (c) 2013, Villa.Gao <>;