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Table of Contents

module.exports

.pino([options], [stream])

Parameters:

  • options (object):
    • safe (boolean): avoid error caused by circular references in the object tree. Default: true.
    • name (string): the name of the logger. Default: undefined.
    • serializers (object): an object containing functions for custom serialization of objects. These functions should return an JSONifiable object and they should never throw. When logging an object, each top-level property matching the exact key of a serializer will be serialized using the defined serializer.
    • timestamp (boolean|function): Enables or disables the inclusion of a timestamp in the log message. If a function is supplied, it must synchronously return a JSON string representation of the time, e.g. ,"time":1493426328206 (which is the default). If set to false`, no timestamp will be included in the output. See stdTimeFunctions for a set of available functions for passing in as a value for this option. Caution: any sort of formatted time will significantly slow down Pino's performance.
    • slowtime (boolean): Outputs ISO time stamps ('2016-03-09T15:18:53.889Z') instead of Epoch time stamps (1457536759176). WARNING: This option carries a 25% performance drop. We recommend using default Epoch timestamps and transforming logs after if required. The pino -t command will do this for you (see CLI). Default: false. Deprecation: this option is scheduled to be removed in Pino 5.0.0. Use timestamp: pino.stdTimeFunctions.slowTime instead.
    • extreme (boolean): Enables extreme mode, yields an additional 60% performance (from 250ms down to 100ms per 10000 ops). There are trade-off's should be understood before usage. See Extreme mode explained. Default: false.
    • level (string): one of 'fatal', 'error', 'warn', 'info', 'debug', 'trace'; also 'silent' is supported to disable logging. Any other value defines a custom level and requires supplying a level value via levelVal. Default: 'info'.
    • levelVal (integer): when defining a custom log level via level, set to an integer value to define the new level. Default: undefined.
    • messageKey (string): the string key for the 'message' in the JSON object. Default msg.
    • prettyPrint (boolean|object): enables pino.pretty. This is intended for non-production configurations. This may be set to a configuration object as outlined in pino.pretty. Default: false.
    • onTerminated (function): this function will be invoked during process shutdown when extreme is set to true. The signature of the function is onTerminated(eventName, err). If you do not specify a function, Pino will invoke process.exit(0) when no error has occurred, and process.exit(1) otherwise. If you do specify a function, it is up to you to terminate the process; you must perform only synchronous operations at this point. See Extreme mode explained for more detail.
    • enabled (boolean): enables logging. Default: true
    • browser (Object): browser only, may have asObject and write keys, see Pino in the Browser
    • base (Object): key-value object added as child logger to each log line. If set to null the base child logger is not added . Default:
      • pid (process.pid)
      • hostname (os.hostname)
      • name of logger if supplied as option
    • crlf (boolean): logs newline delimited JSON with \r\n instead of \n. Default: false.
  • stream (Writable): a writable stream where the logs will be written. It can also receive some log-line metadata, if the relative protocol is enabled. Default: process.stdout

Example:

'use strict'

var pino = require('pino')
var logger = pino({
  name: 'myapp',
  safe: true,
  serializers: {
    req: pino.stdSerializers.req,
    res: pino.stdSerializers.res
  }
})

Discussion:

Returns a new logger instance.

.pretty([options])

Parameters:

  • options (object):
    • timeTransOnly (boolean): if set to true, it will only covert the unix timestamp to ISO 8601 date format, and reserialize the JSON (equivalent to pino -t).
    • formatter (function): a custom function to format the line. It's passed 2 arguments, JSON object log data and an options object that exposes utility functions. It should return a string value.
    • levelFirst (boolean): if set to true, it will print the name of the log level as the first field in the log line. Default: false.
    • messageKey (string): the key in the JSON object to use as the highlighted message. Default: msg.
    • forceColor (boolean): if set to true, will add color information to the formatted output message. Default: false.
    • crlf (boolean): emit \r\n instead of \n. Default: false.

Example:

'use strict'

var pino = require('pino')
var pretty = pino.pretty()
pretty.pipe(process.stdout)
var log = pino({
  name: 'app',
  safe: true
}, pretty)

log.child({ widget: 'foo' }).info('hello')
log.child({ widget: 'bar' }).warn('hello 2')

Discussion:

Provides access to the CLI log prettifier as an API.

This can also be enabled via the constructor by setting the prettyPrint option to either true or a configuration object described in this section.

Logger

.pino

Exposes the current version of Pino.

Example:

var log = require('pino')()
if ('pino' in child) console.log(`pino version: ${log.pino}`)

.child(bindings)

Parameters:

  • bindings (object): an object of key-value pairs to include in log lines as properties.

Example:

logger.child({ a: 'property' }).info('hello child!')
// generates
// {"pid":46497,"hostname":"MacBook-Pro-di-Matteo.local","level":30,"msg":"hello child!","time":1458124707120,"v":0,"a":"property"}

Discussion:

Creates a child logger, setting all key-value pairs in bindings as properties in the log lines. All serializers will be applied to the given pair.

Child loggers use the same output stream as the parent and inherit the current log level of the parent at the time they are spawned.

From v2.x.x the log level of a child is mutable (whereas in v1.x.x it was immutable), and can be set independently of the parent. If a level property is present in the object passed to child it will override the child logger level.

For example:

var logger = pino()
logger.level = 'error'
logger.info('nope') //does not log
var child = logger.child({foo: 'bar'})
child.info('nope again') //does not log
child.level = 'info'
child.info('hooray') //will log
logger.info('nope nope nope') //will not log, level is still set to error
logger.child({ foo: 'bar', level: 'debug' }).debug('debug!')

Child loggers inherit the serializers from the parent logger but it is possible to override them.

For example:

var pino = require('./pino')

var customSerializers = {
  test: function () {
    return 'this is my serializer'
  }
}
var child = pino().child({serializers: customSerializers})

child.info({test: 'should not show up'})

Will produce the following output:

{"pid":7971,"hostname":"mycomputer.local","level":30,"time":1469488147985,"test":"this is my serializer","v":1}

Also from version 2.x.x we can spawn child loggers from child loggers, for instance:

var logger = pino()
var child = logger.child({father: true})
var childChild = child.child({baby: true})

Child logger creation is fast:

benchBunyanCreation*10000: 1291.332ms
benchBoleCreation*10000: 1630.542ms
benchPinoCreation*10000: 352.330ms
benchPinoExtremeCreation*10000: 102.282ms

Logging through a child logger has little performance penalty:

benchBunyanChild*10000: 1343.933ms
benchBoleChild*10000: 1605.969ms
benchPinoChild*10000: 334.573ms
benchPinoExtremeChild*10000: 152.792ms

Spawning children from children has negligible overhead:

benchBunyanChildChild*10000: 1397.202ms
benchPinoChildChild*10000: 338.930ms
benchPinoExtremeChildChild*10000: 150.143ms

.level

Example:

logger.level = 'info'

Discussion:

Set this property to the desired logging level. In order of priority, available levels are:

  1. 'fatal'
  2. 'error'
  3. 'warn'
  4. 'info'
  5. 'debug'
  6. 'trace'

The logging level is a minimum level. For instance if logger.level is 'info' then all 'fatal', 'error', 'warn', and 'info' logs will be enabled.

You can pass 'silent' to disable logging.

.fatal([obj], msg, [...])

Parameters:

  • obj (object): object to be serialized
  • msg (string): the log message to write
  • ... (*): format string values when msg is a format string

Discussion:

Log at 'fatal' level the given msg. If the first argument is an object, all its properties will be included in the JSON line. If more args follows msg, these will be used to format msg using util.format.

.error([obj], msg, [...])

Parameters:

  • obj (object): object to be serialized
  • msg (string): the log message to write
  • ... (*): format string values when msg is a format string

Discussion:

Log at 'error' level the given msg. If the first argument is an object, all its properties will be included in the JSON line. If more args follows msg, these will be used to format msg using util.format.

.warn([obj], msg, [...])

Parameters:

  • obj (object): object to be serialized
  • msg (string): the log message to write
  • ... (*): format string values when msg is a format string

Discussion:

Log at 'warn' level the given msg. If the first argument is an object, all its properties will be included in the JSON line. If more args follows msg, these will be used to format msg using util.format.

.info([obj], msg, [...])

Parameters:

  • obj (object): object to be serialized
  • msg (string): the log message to write
  • ... (*): format string values when msg is a format string

Discussion:

Log at 'info' level the given msg. If the first argument is an object, all its properties will be included in the JSON line. If more args follows msg, these will be used to format msg using util.format.

.debug([obj], msg, [...])

Parameters:

  • obj (object): object to be serialized
  • msg (string): the log message to write
  • ... (*): format string values when msg is a format string

Discussion:

Log at 'debug' level the given msg. If the first argument is an object, all its properties will be included in the JSON line. If more args follows msg, these will be used to format msg using util.format.

.trace([obj], msg, [...])

Parameters:

  • obj (object): object to be serialized
  • msg (string): the log message to write
  • ... (*): format string values when msg is a format string

Discussion:

Log at 'trace' level the given msg. If the first argument is an object, all its properties will be included in the JSON line. If more args follows msg, these will be used to format msg using util.format.

.flush()

Discussion:

Flushes the content of the buffer in extreme mode. It has no effect if extreme mode is not enabled.

.addLevel(name, lvl)

Parameters:

  • name (string): defines the method name of the new level
  • lvl (integer): value for the level, e.g. 35 is between info and warn

Example:

var pino = require('pino')
var log = pino()
log.addLevel('myLevel', 35)
log.level = 'myLevel'
log.myLevel('a message')

Discussion:

Defines a new level on the logger instance. Returns true on success and false if there was a conflict (level name or number already exists).

When using this method, the current level of the logger instance does not change. You must adjust the level with the level property after adding your custom level.

If you need a custom level at construction, you can supply the level and levelVal options:

var pino = require('pino')
var log = pino({level: 'myLevel', levelVal: 35})
log.myLevel('a message')

The level is set to the custom level on construction, i.e. log.level does not need to be set.

.levelVal

Example:

if (logger.levelVal === 30) {
  console.log('logger level is `info`')
}

Discussion:

Returns the integer value for the logger instance's logging level.

.on('level-change', fn)

Example:

var listener = function (lvl, val, prevLvl, prevVal) {
  console.log(lvl, val, prevLvl, prevVal)
}
logger.on('level-change', listener)
logger.level = 'trace' // trigger console message
logger.removeListener('level-change', listener)
logger.level = 'info' // no message, since listener was removed

Discussion:

Registers a listener function that is triggered when the level is changed.

The listener is passed four arguments: levelLabel, levelValue, previousLevelLabel, previousLevelValue.

Note: When browserified, this functionality will only be available if the events module has been required elsewhere (e.g. if you're using streams in the browser). This allows for a trade-off between bundle size and functionality.

.levels.values

Example:

pino.levels.values.error === 50 // true

Discussion:

Returns the mappings of level names to their respective internal number representation. This property is available as a static property or as an instance property.

.levels.labels

Example:

pino.levels.labels[50] === 'error' // true

Discussion:

Returns the mappings of level internal level numbers to their string representations. This property is available as a static property or as an instance property.

.isLevelEnabled(logLevel)

Example:

if (logger.isLevelEnabled('debug')) logger.debug('conditional log')

Discussion:

A utility method for determining if a given log level will write to the output stream.

.LOG_VERSION

Discussion:

Read only. Holds the current log format version (as output in the v property of each log record). This property is available as a static property or as an instance property.

.stdSerializers

Available as a static property, the stdSerializers provide functions for serializing objects common to many projects.

.req

Generates a JSONifiable object from the HTTP request object passed to the createServer callback of Node's HTTP server.

It returns an object in the form:

{
  pid: 93535,
  hostname: 'your host',
  level: 30,
  msg: 'my request',
  time: '2016-03-07T12:21:48.766Z',
  v: 0,
  req: {
    method: 'GET',
    url: '/',
    headers: {
      host: 'localhost:50201',
      connection: 'close'
    },
    remoteAddress: '::ffff:127.0.0.1',
    remotePort: 50202
  }
}

.res

Generates a JSONifiable object from the HTTP response object passed to the createServer callback of Node's HTTP server.

It returns an object in the form:

{
  pid: 93581,
  hostname: 'myhost',
  level: 30,
  msg: 'my response',
  time: '2016-03-07T12:23:18.041Z',
  v: 0,
  res: {
    statusCode: 200,
    header: 'HTTP/1.1 200 OK\r\nDate: Mon, 07 Mar 2016 12:23:18 GMT\r\nConnection: close\r\nContent-Length: 5\r\n\r\n'
  }
}

.err

Serializes an Error object if passed in as an property.

{
  "pid": 40510,
  "hostname": "MBP-di-Matteo",
  "level": 50,
  "msg": "an error",
  "time": 1459433282301,
  "v": 1,
  "type": "Error",
  "stack": "Error: an error\n    at Object.<anonymous> (/Users/matteo/Repositories/pino/example.js:16:7)\n    at Module._compile (module.js:435:26)\n    at Object.Module._extensions..js (module.js:442:10)\n    at Module.load (module.js:356:32)\n    at Function.Module._load (module.js:313:12)\n    at Function.Module.runMain (module.js:467:10)\n    at startup (node.js:136:18)\n    at node.js:963:3"
}

.stdTimeFunctions

Available as a static property, the stdTimeFunctions provide functions for generating the timestamp property in the log output. You can set the timestamp option during initialization to one of these functions to adjust the output format. Alternatively, you can specify your own time function.

A time function must synchronously return a string that would be a valid component of a JSON string. For example, the default function returns a string like ,"time":1493426328206.

.epochTime

The default time function for Pino. Returns a string like ,"time":1493426328206.

.unixTime

Returns a unix time in seconds, like ,"time":1493426328.

.slowTime

Returns an ISO formatted string like `,"time":"2017-04-29T00:47:49.354Z". It is highly recommended that you avoid this function. It incurs a significant performance penalty.

.nulltime

Returns an empty string. This function is used when the timestamp option is set to false.

Metadata

A destination stream can have a property stream[Symbol.for('needsMetadata')] = true to indicate that for every log line written, the following properties of the stream should be set:

  • the last logging level as stream.lastLevel
  • the last logging message as stream.lastMsg
  • the last logging object as stream.lastObj
  • the last logger instance as stream.lastLogger (to support child loggers)

Example

var instance = pino({}, {
  [Symbol.for('needsMetadata')]: true,
  write: function (chunk) {
    console.log('lastLevel', this.lastLevel)
    console.log('lastMsg', this.lastMsg)
    console.log('lastObj', this.lastObj)
    console.log('lastLogger', this.lastLogger)
    console.log('line', chunk)
  }
})