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HTTP request logger middleware for node.js

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# morgan

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HTTP request logger middleware for node.js

> Named after [Dexter](https://en.wikipedia.org/wiki/Dexter_Morgan), a show you should not watch until completion.

## Installation

This is a [Node.js](https://nodejs.org/en/) module available through the
[npm registry](https://www.npmjs.com/). Installation is done using the
[`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally):

```sh
$ npm install morgan
```

## API

```js
var morgan = require('morgan')
```

### morgan(format, options)

Create a new morgan logger middleware function using the given `format` and `options`.
The `format` argument may be a string of a predefined name (see below for the names),
a string of a format string, or a function that will produce a log entry.

The `format` function will be called with three arguments `tokens`, `req`, and `res`,
where `tokens` is an object with all defined tokens, `req` is the HTTP request and `res`
is the HTTP response. The function is expected to return a string that will be the log
line, or `undefined` / `null` to skip logging.

#### Using a predefined format string

```js
morgan('tiny')
```

#### Using format string of predefined tokens

```js
morgan(':method :url :status :res[content-length] - :response-time ms')
```

#### Using a custom format function

``` js
morgan(function (tokens, req, res) {
  return [
    tokens.method(req, res),
    tokens.url(req, res),
    tokens.status(req, res),
    tokens.res(req, res, 'content-length'), '-',
    tokens['response-time'](req, res), 'ms'
  ].join(' ')
})
```

#### Options

Morgan accepts these properties in the options object.

##### immediate

Write log line on request instead of response. This means that a requests will
be logged even if the server crashes, _but data from the response (like the
response code, content length, etc.) cannot be logged_.

##### skip

Function to determine if logging is skipped, defaults to `false`. This function
will be called as `skip(req, res)`.

```js
// EXAMPLE: only log error responses
morgan('combined', {
  skip: function (req, res) { return res.statusCode < 400 }
})
```

##### stream

Output stream for writing log lines, defaults to `process.stdout`.

#### Predefined Formats

There are various pre-defined formats provided:

##### combined

Standard Apache combined log output.
```
:remote-addr - :remote-user [:date[clf]] ":method :url HTTP/:http-version" :status :res[content-length] ":referrer" ":user-agent"
# will output
::1 - - [27/Nov/2024:06:21:42 +0000] "GET /combined HTTP/1.1" 200 2 "-" "curl/8.7.1"
```

##### common

Standard Apache common log output.

```
:remote-addr - :remote-user [:date[clf]] ":method :url HTTP/:http-version" :status :res[content-length]
# will output
::1 - - [27/Nov/2024:06:21:46 +0000] "GET /common HTTP/1.1" 200 2
```

##### dev

Concise output colored by response status for development use. The `:status`
token will be colored green for success codes, red for server error codes,
yellow for client error codes, cyan for redirection codes, and uncolored
for information codes.

```
:method :url :status :response-time ms - :res[content-length]
# will output
GET /dev 200 0.224 ms - 2
```

##### short

Shorter than default, also including response time.

```
:remote-addr :remote-user :method :url HTTP/:http-version :status :res[content-length] - :response-time ms
# will output
::1 - GET /short HTTP/1.1 200 2 - 0.283 ms
```

##### tiny

The minimal output.

```
:method :url :status :res[content-length] - :response-time ms
# will output
GET /tiny 200 2 - 0.188 ms
```

#### Tokens

##### Creating new tokens

To define a token, simply invoke `morgan.token()` with the name and a callback function.
This callback function is expected to return a string value. The value returned is then
available as ":type" in this case:

```js
morgan.token('type', function (req, res) { return req.headers['content-type'] })
```

Calling `morgan.token()` using the same name as an existing token will overwrite that
token definition.

The token function is expected to be called with the arguments `req` and `res`, representing
the HTTP request and HTTP response. Additionally, the token can accept further arguments of
it's choosing to customize behavior.

##### :date[format]

The current date and time in UTC. The available formats are:

- `clf` for the common log format (`"10/Oct/2000:13:55:36 +0000"`)
  - `iso` for the common ISO 8601 date time format (`2000-10-10T13:55:36.000Z`)
  - `web` for the common RFC 1123 date time format (`Tue, 10 Oct 2000 13:55:36 GMT`)

If no format is given, then the default is `web`.

##### :http-version

The HTTP version of the request.

##### :method

The HTTP method of the request.

##### :pid

The process ID of the Node.js process handling the request.

##### :referrer

The Referrer header of the request. This will use the standard mis-spelled Referer header if exists, otherwise Referrer.

##### :remote-addr

The remote address of the request. This will use `req.ip`, otherwise the standard `req.connection.remoteAddress` value (socket address).

##### :remote-user

The user authenticated as part of Basic auth for the request.

##### :req[header]

The given `header` of the request. If the header is not present, the
value will be displayed as `"-"` in the log.

##### :res[header]

The given `header` of the response. If the header is not present, the
value will be displayed as `"-"` in the log.

##### :response-time[digits]

The time between the request coming into `morgan` and when the response
headers are written, in milliseconds.

The `digits` argument is a number that specifies the number of digits to
include on the number, defaulting to `3`, which provides microsecond precision.

##### :status

The status code of the response.

If the request/response cycle completes before a response was sent to the
client (for example, the TCP socket closed prematurely by a client aborting
the request), then the status will be empty (displayed as `"-"` in the log).

##### :total-time[digits]

The time between the request coming into `morgan` and when the response
has finished being written out to the connection, in milliseconds.

The `digits` argument is a number that specifies the number of digits to
include on the number, defaulting to `3`, which provides microsecond precision.

##### :url

The URL of the request. This will use `req.originalUrl` if exists, otherwise `req.url`.

##### :user-agent

The contents of the User-Agent header of the request.

### morgan.compile(format)

Compile a format string into a `format` function for use by `morgan`. A format string
is a string that represents a single log line and can utilize token syntax.
Tokens are references by `:token-name`. If tokens accept arguments, they can
be passed using `[]`, for example: `:token-name[pretty]` would pass the string
`'pretty'` as an argument to the token `token-name`.

The function returned from `morgan.compile` takes three arguments `tokens`, `req`, and
`res`, where `tokens` is object with all defined tokens, `req` is the HTTP request and
`res` is the HTTP response. The function will return a string that will be the log line,
or `undefined` / `null` to skip logging.

Normally formats are defined using `morgan.format(name, format)`, but for certain
advanced uses, this compile function is directly available.

## Examples

### express/connect

Sample app that will log all request in the Apache combined format to STDOUT

```js
var express = require('express')
var morgan = require('morgan')

var app = express()

app.use(morgan('combined'))

app.get('/', function (req, res) {
  res.send('hello, world!')
})
```

### vanilla http server

Sample app that will log all request in the Apache combined format to STDOUT

```js
var finalhandler = require('finalhandler')
var http = require('http')
var morgan = require('morgan')

// create "middleware"
var logger = morgan('combined')

http.createServer(function (req, res) {
  var done = finalhandler(req, res)
  logger(req, res, function (err) {
    if (err) return done(err)

// respond to request
    res.setHeader('content-type', 'text/plain')
    res.end('hello, world!')
  })
})
```

### write logs to a file

#### single file

Sample app that will log all requests in the Apache combined format to the file
`access.log`.

```js
var express = require('express')
var fs = require('fs')
var morgan = require('morgan')
var path = require('path')

var app = express()

// create a write stream (in append mode)
var accessLogStream = fs.createWriteStream(path.join(__dirname, 'access.log'), { flags: 'a' })

// setup the logger
app.use(morgan('combined', { stream: accessLogStream }))

app.get('/', function (req, res) {
  res.send('hello, world!')
})
```

#### log file rotation

Sample app that will log all requests in the Apache combined format to one log
file per day in the `log/` directory using the
[rotating-file-stream module](https://www.npmjs.com/package/rotating-file-stream).

```js
var express = require('express')
var morgan = require('morgan')
var path = require('path')
var rfs = require('rotating-file-stream') // version 2.x

var app = express()

// create a rotating write stream
var accessLogStream = rfs.createStream('access.log', {
  interval: '1d', // rotate daily
  path: path.join(__dirname, 'log')
})

// setup the logger
app.use(morgan('combined', { stream: accessLogStream }))

app.get('/', function (req, res) {
  res.send('hello, world!')
})
```

### split / dual logging

The `morgan` middleware can be used as many times as needed, enabling
combinations like:

* Log entry on request and one on response
  * Log all requests to file, but errors to console
  * ... and more!

Sample app that will log all requests to a file using Apache format, but
error responses are logged to the console:

```js
var express = require('express')
var fs = require('fs')
var morgan = require('morgan')
var path = require('path')

var app = express()

// log only 4xx and 5xx responses to console
app.use(morgan('dev', {
  skip: function (req, res) { return res.statusCode < 400 }
}))

// log all requests to access.log
app.use(morgan('common', {
  stream: fs.createWriteStream(path.join(__dirname, 'access.log'), { flags: 'a' })
}))

app.get('/', function (req, res) {
  res.send('hello, world!')
})
```

### use custom token formats

Sample app that will use custom token formats. This adds an ID to all requests and displays it using the `:id` token.

```js
var express = require('express')
var morgan = require('morgan')
var uuid = require('node-uuid')

morgan.token('id', function getId (req) {
  return req.id
})

var app = express()

app.use(assignId)
app.use(morgan(':id :method :url :response-time'))

app.get('/', function (req, res) {
  res.send('hello, world!')
})

function assignId (req, res, next) {
  req.id = uuid.v4()
  next()
}
```

## License

[MIT](LICENSE)

[ci-image]: https://badgen.net/github/checks/expressjs/morgan/master?label=ci
[ci-url]: https://github.com/expressjs/morgan/actions/workflows/ci.yml
[coveralls-image]: https://badgen.net/coveralls/c/github/expressjs/morgan/master
[coveralls-url]: https://coveralls.io/r/expressjs/morgan?branch=master
[npm-downloads-image]: https://badgen.net/npm/dm/morgan
[npm-url]: https://npmjs.org/package/morgan
[npm-version-image]: https://badgen.net/npm/v/morgan

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