29 KiB
API
pino([options], [destination]) => logger
The exported pino
function takes two optional arguments,
options
and destination
and
returns a logger instance.
options
(Object)
name
(String)
Default: undefined
The name of the logger. When set adds a name
field to every JSON line logged.
level
(String)
Default: 'info'
One of 'fatal'
, 'error'
, 'warn'
, 'info
', 'debug'
, 'trace'
or 'silent'
.
Additional levels can be added to the instance via the customLevels
option.
customLevels
(Object)
Default: undefined
Use this option to define additional logging levels. The keys of the object correspond the namespace of the log level, and the values should be the numerical value of the level.
const logger = pino({
customLevels: {
foo: 35
}
})
logger.foo('hi')
useOnlyCustomLevels
(Boolean)
Default: false
Use this option to only use defined customLevels
and omit Pino's levels.
Logger's default level
must be changed to a value in customLevels
in order to use useOnlyCustomLevels
Warning: this option may not be supported by downstream transports.
const logger = pino({
customLevels: {
foo: 35
},
useOnlyCustomLevels: true,
level: 'foo'
})
logger.foo('hi')
logger.info('hello') // Will throw an error saying info in not found in logger object
mixin
(Function):
Default: undefined
If provided, the mixin
function is called each time one of the active
logging methods is called. The function must synchronously return an
object. The properties of the returned object will be added to the
logged JSON.
let n = 0
const logger = pino({
mixin () {
return { line: ++n }
}
})
logger.info('hello')
// {"level":30,"time":1573664685466,"pid":78742,"hostname":"x","line":1,"msg":"hello","v":1}
logger.info('world')
// {"level":30,"time":1573664685469,"pid":78742,"hostname":"x","line":2,"msg":"world","v":1}
redact
(Array | Object):
Default: undefined
As an array, the redact
option specifies paths that should
have their values redacted from any log output.
Each path must be a string using a syntax which corresponds to JavaScript dot and bracket notation.
If an object is supplied, three options can be specified:
paths
(array): Required. An array of paths. See redaction - Path Syntax ⇗ for specifics.censor
(String|Function|Undefined): Optional. When supplied as a String thecensor
option will overwrite keys which are to be redacted. When set toundefined
the the key will be removed entirely from the object. Thecensor
option may also be a mapping function. The (synchronous) mapping function is called with the unredacted value. The value returned from the mapping function becomes the applied censor value. Default:'[Redacted]'
value synchronously. Default:'[Redacted]'
remove
(Boolean): Optional. Instead of censoring the value, remove both the key and the value. Default:false
WARNING: Never allow user input to define redacted paths.
- See the redaction ⇗ documentation.
- See fast-redact#caveat ⇗
serializers
(Object)
Default: {err: pino.stdSerializers.err}
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.
serializers[Symbol.for('pino.*')]
(Function)
Default: undefined
The serializers
object may contain a key which is the global symbol: Symbol.for('pino.*')
.
This will act upon the complete log object rather than corresponding to a particular key.
base
(Object)
Default: {pid: process.pid, hostname: os.hostname}
Key-value object added as child logger to each log line.
Set to null
to avoid adding pid
, hostname
and name
properties to each log.
enabled
(Boolean)
Default: true
Set to false
to disable logging.
crlf
(Boolean)
Default: false
Set to true
to logs newline delimited JSON with \r\n
instead of \n
.
timestamp
(Boolean | Function)
Default: true
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: attempting to format time in-process will significantly impact logging performance.
messageKey
(String)
Default: 'msg'
The string key for the 'message' in the JSON object.
nestedKey
(String)
Default: null
If there's a chance that objects being logged have properties that conflict with those from pino itself (level
, timestamp
, v
, pid
, etc)
and duplicate keys in your log records are undesirable, pino can be configured with a nestedKey
option that causes any object
s that are logged
to be placed under a key whose name is the value of nestedKey
.
This way, when searching something like Kibana for values, one can consistently search under the configured nestedKey
value instead of the root log record keys.
For example,
const logger = require('pino')({
nestedKey: 'payload'
})
const thing = { level: 'hi', time: 'never', foo: 'bar'} // has pino-conflicting properties!
logger.info(thing)
// logs the following:
// {"level":30,"time":1578357790020,"pid":91736,"hostname":"x","payload":{"level":"hi","time":"never","foo":"bar"},"v":1}
In this way, logged objects' properties don't conflict with pino's standard logging properties, and searching for logged objects can start from a consistent path.
prettyPrint
(Boolean | Object)
Default: false
Enables pretty printing log logs. This is intended for non-production
configurations. This may be set to a configuration object as outlined in the
pino-pretty
documentation.
The options object may additionally contain a prettifier
property to define
which prettifier module to use. When not present, prettifier
defaults to
'pino-pretty'
. Regardless of the value, the specified prettifier module
must be installed as a separate dependency:
npm install pino-pretty
useLevelLabels
(Boolean)
Default: false
Enables printing of level labels instead of level values in the printed logs. Warning: this option may not be supported by downstream transports.
changeLevelName
(String) - DEPRECATED
Use levelKey
instead. This will be removed in v7.
levelKey
(String)
Default: 'level'
Changes the property level
to any string value you pass in:
const logger = pino({
levelKey: 'priority'
})
logger.info('hello world')
// {"priority":30,"time":1531257112193,"msg":"hello world","pid":55956,"hostname":"x","v":1}
browser
(Object)
Browser only, may have asObject
and write
keys. This option is separately
documented in the Browser API ⇗ documentation.
- See Browser API ⇗
destination
(SonicBoom | WritableStream | String)
Default: pino.destination(1)
(STDOUT)
The destination
parameter, at a minimum must be an object with a write
method.
An ordinary Node.js stream
can be passed as the destination (such as the result
of fs.createWriteStream
) but for peak log writing performance it is strongly
recommended to use pino.destination
or pino.extreme
to create the destination stream.
// pino.destination(1) by default
const stdoutLogger = require('pino')()
// destination param may be in first position when no options:
const fileLogger = require('pino')( pino.destination('/log/path'))
// use the stderr file handle to log to stderr:
const opts = {name: 'my-logger'}
const stderrLogger = require('pino')(opts, pino.destination(2))
// automatic wrapping in pino.destination
const fileLogger = require('pino')('/log/path')
However, there are some special instances where pino.destination
is not used as the default:
- When something, e.g a process manager, has monkey-patched
process.stdout.write
.
In these cases process.stdout
is used instead.
- See
pino.destination
- See
pino.extreme
destination[Symbol.for('pino.metadata')]
Default: false
Using the global symbol Symbol.for('pino.metadata')
as a key on the destination
parameter and
setting the key it to true
, indicates that the following properties should be
set on the destination
object after each log line is written:
- the last logging level as
destination.lastLevel
- the last logging message as
destination.lastMsg
- the last logging object as
destination.lastObj
- the last time as
destination.lastTime
, which will be the partial string returned by the time function. - the last logger instance as
destination.lastLogger
(to support child loggers)
For a full reference for using Symbol.for('pino.metadata')
, see the pino-multi-stream
⇗
module.
The following is a succinct usage example:
const dest = pino.destination('/dev/null')
dest[Symbol.for('pino.metadata')] = true
const logger = pino(dest)
logger.info({a: 1}, 'hi')
const { lastMsg, lastLevel, lastObj, lastTime} = dest
console.log(
'Logged message "%s" at level %d with object %o at time %s',
lastMsg, lastLevel, lastObj, lastTime
) // Logged message "hi" at level 30 with object { a: 1 } at time 1531590545089
Logger Instance
The logger instance is the object returned by the main exported
pino
function.
The primary purpose of the logger instance is to provide logging methods.
The default logging methods are trace
, debug
, info
, warn
, error
, and fatal
.
Each logging method has the following signature:
([mergingObject], [message], [...interpolationValues])
.
The parameters are explained below using the logger.info
method but the same applies to all logging methods.
Logging Method Parameters
mergingObject
(Object)
An object can optionally be supplied as the first parameter. Each enumerable key and value
of the mergingObject
is copied in to the JSON log line.
logger.info({MIX: {IN: true}})
// {"level":30,"time":1531254555820,"pid":55956,"hostname":"x","MIX":{"IN":true},"v":1}
message
(String)
A message
string can optionally be supplied as the first parameter, or
as the second parameter after supplying a mergingObject
.
By default, the contents of the message
parameter will be merged into the
JSON log line under the msg
key:
logger.info('hello world')
// {"level":30,"time":1531257112193,"msg":"hello world","pid":55956,"hostname":"x","v":1}
The message
parameter takes precedence over the mergedObject
.
That is, if a mergedObject
contains a msg
property, and a message
parameter
is supplied in addition, the msg
property in the output log will be the value of
the message
parameter not the value of the msg
property on the mergedObject
.
The messageKey
option can be used at instantiation time to change the namespace
from msg
to another string as preferred.
The message
string may contain a printf style string with support for
the following placeholders:
%s
– string placeholder%d
– digit placeholder%O
,%o
and%j
– object placeholder
Values supplied as additional arguments to the logger method will then be interpolated accordingly.
...interpolationValues
(Any)
All arguments supplied after message
are serialized and interpolated according
to any supplied printf-style placeholders (%s
, %d
, %o
|%O
|%j
)
or else concatenated together with the message
string to form the final
output msg
value for the JSON log line.
logger.info('hello', 'world')
// {"level":30,"time":1531257618044,"msg":"hello world","pid":55956,"hostname":"x","v":1}
logger.info('hello', {worldly: 1})
// {"level":30,"time":1531257797727,"msg":"hello {\"worldly\":1}","pid":55956,"hostname":"x","v":1}
logger.info('%o hello', {worldly: 1})
// {"level":30,"time":1531257826880,"msg":"{\"worldly\":1} hello","pid":55956,"hostname":"x","v":1}
logger.trace([mergingObject], [message], [...interpolationValues])
Write a 'trace'
level log, if the configured level
allows for it.
- See
mergingObject
log method parameter - See
message
log method parameter - See
...interpolationValues
log method parameter
logger.debug([mergingObject], [message], [...interpolationValues])
Write a 'debug'
level log, if the configured level
allows for it.
- See
mergingObject
log method parameter - See
message
log method parameter - See
...interpolationValues
log method parameter
logger.info([mergingObject], [message], [...interpolationValues])
Write an 'info'
level log, if the configured level
allows for it.
- See
mergingObject
log method parameter - See
message
log method parameter - See
...interpolationValues
log method parameter
logger.warn([mergingObject], [message], [...interpolationValues])
Write a 'warn'
level log, if the configured level
allows for it.
- See
mergingObject
log method parameter - See
message
log method parameter - See
...interpolationValues
log method parameter
logger.error([mergingObject], [message], [...interpolationValues])
Write a 'error'
level log, if the configured level
allows for it.
- See
mergingObject
log method parameter - See
message
log method parameter - See
...interpolationValues
log method parameter
logger.fatal([mergingObject], [message], [...interpolationValues])
Write a 'fatal'
level log, if the configured level
allows for it.
Since 'fatal'
level messages are intended to be logged just prior to the process exiting the fatal
method will always sync flush the destination.
Therefore it's important not to misuse fatal
since
it will cause performance overhead if used for any
other purpose than writing final log messages before
the process crashes or exits.
- See
mergingObject
log method parameter - See
message
log method parameter - See
...interpolationValues
log method parameter
logger.child(bindings) => logger
The logger.child
method allows for the creation of stateful loggers,
where key-value pairs can be pinned to a logger causing them to be output
on every log line.
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.
The log level of a child is mutable. It can be set independently
of the parent either by setting the level
accessor after creating
the child logger or using the reserved bindings.level
key.
bindings
(Object)
An object of key-value pairs to include in every log line output via the returned child logger.
const child = logger.child({ MIX: {IN: 'always'} })
child.info('hello')
// {"level":30,"time":1531258616689,"msg":"hello","pid":64849,"hostname":"x","MIX":{"IN":"always"},"v":1}
child.info('child!')
// {"level":30,"time":1531258617401,"msg":"child!","pid":64849,"hostname":"x","MIX":{"IN":"always"},"v":1}
The bindings
object may contain any key except for reserved configuration keys level
and serializers
.
bindings.level
(String)
If a level
property is present in the bindings
object passed to logger.child
it will override the child logger level.
const logger = pino()
logger.debug('nope') // will not log, since default level is info
const child = logger.child({foo: 'bar', level: 'debug'})
child.debug('debug!') // will log as the `level` property set the level to debug
bindings.serializers
(Object)
Child loggers inherit the serializers from the parent logger.
Setting the serializers
key of the bindings
object will override
any configured parent serializers.
const logger = require('pino')()
logger.info({test: 'will appear'})
// {"level":30,"time":1531259759482,"pid":67930,"hostname":"x","test":"will appear","v":1}
const child = logger.child({serializers: {test: () => `child-only serializer`}})
child.info({test: 'will be overwritten'})
// {"level":30,"time":1531259784008,"pid":67930,"hostname":"x","test":"child-only serializer","v":1}
logger.bindings()
Returns an object containing all the current bindings, cloned from the ones passed in via logger.child()
.
const child = logger.child({ foo: 'bar' })
console.log(child.bindings())
// { foo: 'bar' }
const anotherChild = child.child({ MIX: { IN: 'always' } })
console.log(anotherChild.bindings())
// { foo: 'bar', MIX: { IN: 'always' } }
logger.flush()
Flushes the content of the buffer when using a pino.extreme
destination.
This is an asynchronous, fire and forget, operation.
The use case is primarily for Extreme mode logging, which may hold up to
4KiB of logs. The logger.flush
method can be used to flush the logs
on an long interval, say ten seconds. Such a strategy can provide an
optimium balance between extremely efficient logging at high demand periods
and safer logging at low demand periods.
- See
pino.extreme
- See
destination
parameter - See Extreme mode ⇗
logger.level
(String) [Getter/Setter]
Set this property to the desired logging level.
The core levels and their values are as follows:
Level: | trace | debug | info | warn | error | fatal | silent |
Value: | 10 | 20 | 30 | 40 | 50 | 60 | Infinity |
The logging level is a minimum level based on the associated value of that level.
For instance if logger.level
is info
(30) then info
(30), warn
(40), error
(50) and fatal
(60) log methods will be enabled but the trace
(10) and debug
(20) methods, being less than 30, will not.
The silent
logging level is a specialized level which will disable all logging,
there is no silent
log method.
logger.isLevelEnabled(level)
A utility method for determining if a given log level will write to the destination.
level
(String)
The given level to check against:
if (logger.isLevelEnabled('debug')) logger.debug('conditional log')
levelLabel
(String)
Defines the method name of the new level.
- See
logger.level
levelValue
(Number)
Defines the associated minimum threshold value for the level, and therefore where it sits in order of priority among other levels.
- See
logger.level
logger.levelVal
(Number)
Supplies the integer value for the current logging level.
if (logger.levelVal === 30) {
console.log('logger level is `info`')
}
logger.levels
(Object)
Levels are mapped to values to determine the minimum threshold that a
logging method should be enabled at (see logger.level
).
The logger.levels
property holds the mappings between levels and values,
and vice versa.
$ node -p "require('pino')().levels"
{ labels:
{ '10': 'trace',
'20': 'debug',
'30': 'info',
'40': 'warn',
'50': 'error',
'60': 'fatal' },
values:
{ fatal: 60, error: 50, warn: 40, info: 30, debug: 20, trace: 10 } }
- See
logger.level
logger[Symbol.for('pino.serializers')]
Returns the serializers as applied to the current logger instance. If a child logger did not register it's own serializer upon instantiation the serializers of the parent will be returned.
Event: 'level-change'
The logger instance is also an EventEmitter ⇗
A listener function can be attached to a logger via the level-change
event
The listener is passed four arguments:
levelLabel
– the new level string, e.gtrace
levelValue
– the new level number, e.g10
previousLevelLabel
– the prior level string, e.ginfo
previousLevelValue
– the prior level numbebr, e.g30
const logger = require('pino')()
logger.on('level-change', (lvl, val, prevLvl, prevVal) => {
console.log('%s (%d) was changed to %s (%d)', lvl, val, prevLvl, prevVal)
})
logger.level = 'trace' // trigger event
logger.version
(String)
Exposes the Pino package version. Also available on the exported pino
function.
- See
pino.version
logger.LOG_VERSION
(Number)
Holds the current log format version as output in the v
property of each log record.
Also available on the exported pino
function.
- See
pino.LOG_VERSION
Statics
pino.destination([target]) => SonicBoom
Create a Pino Destination instance: a stream-like object with significantly more throughput (over 30%) than a standard Node.js stream.
const pino = require('pino')
const logger = pino(pino.destination('./my-file'))
const logger2 = pino(pino.destination())
The pino.destination
method may be passed a file path or a numerical file descriptor.
By default, pino.destination
will use process.stdout.fd
(1) as the file descriptor.
pino.destination
is implemented on sonic-boom
⇗.
A pino.destination
instance can also be used to reopen closed files
(for example, for some log rotation scenarios), see Reopening log files.
- See
destination
parameter - See
sonic-boom
⇗ - See Reopening log files
pino.extreme([target]) => SonicBoom
Create an extreme mode destination. This yields an additional 60% performance boost. There are trade-offs that should be understood before usage.
const pino = require('pino')
const logger = pino(pino.extreme('./my-file'))
const logger2 = pino(pino.extreme())
The pino.extreme
method may be passed a file path or a numerical file descriptor.
By default, pino.extreme
will use process.stdout.fd
(1) as the file descriptor.
pino.extreme
is implemented with the sonic-boom
⇗
module.
A pino.extreme
instance can also be used to reopen closed files
(for example, for some log rotation scenarios), see Reopening log files.
On AWS Lambda we recommend to call extreme.flushSync()
at the end
of each function execution to avoid losing data.
- See
destination
parameter - See
sonic-boom
⇗ - See Extreme mode ⇗
- See Reopening log files
pino.final(logger, [handler]) => Function | FinalLogger
The pino.final
method can be used to acquire a final logger instance
or create an exit listener function.
The finalLogger
is a specialist logger that synchronously flushes
on every write. This is important to guarantee final log writes,
both when using pino.extreme
target.
Since final log writes cannot be guaranteed with normal Node.js streams,
if the destination
parameter of the logger
supplied to pino.final
is a Node.js stream pino.final
will throw.
The use of pino.final
with pino.destination
is not needed, as
pino.destination
writes things synchronously.
pino.final(logger, handler) => Function
In this case the pino.final
method supplies an exit listener function that can be
supplied to process exit events such as exit
, uncaughtException
,
SIGHUP
and so on.
The exit listener function will call the supplied handler
function
with an error object (or else null
), a finalLogger
instance followed
by any additional arguments the handler
may be called with.
process.on('uncaughtException', pino.final(logger, (err, finalLogger) => {
finalLogger.error(err, 'uncaughtException')
process.exit(1)
}))
pino.final(logger) => FinalLogger
In this case the pino.final
method returns a finalLogger instance.
var finalLogger = pino.final(logger)
finalLogger.info('exiting...')
- See
destination
parameter - See Exit logging help
- See Extreme mode ⇗
- See Log loss prevention ⇗
pino.stdSerializers
(Object)
The pino.stdSerializers
object provides functions for serializing objects common to many projects. The standard serializers are directly imported from pino-std-serializers.
pino.stdTimeFunctions
(Object)
The timestamp
option can accept a function which determines the
timestamp
value in a log line.
The pino.stdTimeFunctions
object provides a very small set of common functions for generating the
timestamp
property. These consist of the following
-
pino.stdTimeFunctions.epochTime
: Milliseconds since Unix epoch (Default) -
pino.stdTimeFunctions.unixTime
: Seconds since Unix epoch -
pino.stdTimeFunctions.nullTime
: Clears timestamp property (Used whentimestamp: false
) -
pino.stdTimeFunctions.isoTime
: ISO 8601-formatted time in UTC -
See
timestamp
option
pino.symbols
(Object)
For integration purposes with ecosystem and third party libraries pino.symbols
exposes the symbols used to hold non-public state and methods on the logger instance.
Access to the symbols allows logger state to be adjusted, and methods to be overridden or proxied for performant integration where necessary.
The pino.symbols
object is intended for library implementers and shouldn't be utilized
for general use.
pino.version
(String)
Exposes the Pino package version. Also available on the logger instance.
- See
logger.version
pino.LOG_VERSION
(Number)
Holds the current log format version as output in the v
property of each log record. Also available on the logger instance.