LSK.js – log
@lskjs/log – Логгер совмещающий лучшие черты morgan, winston, bunyan, logrus. debug. Базируется на debug-level.
Table of contents
⌨️ Install
yarn i @lskjs/log
npm i @lskjs/log
Installation
$ npm install --save @lskjs/log
Usage
@lskjs/log
provides 6 log levels which are trace
, debug
, info
, warn
, error
,
fatal
, and off
.
Each level has a corresponding method debug
-> log.debug
... fatal
-->
log.fatal
which shall be used to indicated the level to log.
The characters %s
, %d
, %i
, %f
, %j
, %o
, %O
, %%
are supported formatters when
given in the first argument.
examples/levels.js
const Log = require('@lskjs/log')
const log = new Log('test')
const log = require('@lskjs/log').log('test')
log.fatal(new Error('fatal'))
log.error(new Error('boom'))
log.warn('huh %o', {ghost: 'rider'})
log.info('%s world', 'hello')
log.debug({object: 1})
log.log('always logs')
Running levels.js
without environment variables will show no output (apart from log.log
).
Setting only DEBUG_LEVEL
shows all lines with their respective level.
Combined with DEBUG
, using comma separated namespaces, only
those log lines with matching namespace and level get logged.
The following table gives an overview of possible combinations:
DEBUG_LEVEL | DEBUG | Output |
---|
-- | -- | no output |
fatal | -- | logs only log.fatal |
error | -- | log.fatal, log.error |
warn | -- | log.fatal, log.error, log.warn |
info | -- | log.fatal, log.error, log.warn and log.info |
debug | -- | log.fatal, log.error, log.warn, log.info and log.debug |
trace | -- | log.fatal, log.error, log.warn, log.info, log.debug and log.trace |
-- | <namespaces> | log.fatal, to log.debug which apply to <namespaces> . Same behavior as debug. |
fatal | <namespaces> | log.fatal for all <namespaces> only |
error | <namespaces> | log.fatal, log.error for <namespaces> only |
warn | <namespaces> | log.fatal, to log.warn for <namespaces> only |
info | <namespaces> | log.fatal, to log.info for <namespaces> only |
debug | <namespaces> | log.fatal, to log.debug for <namespaces> only |
trace | <namespaces> | log.fatal, to log.trace for <namespaces> only |
-- | error:n1,debug:n2,fatal:* | Logs namespace n1 at level error , namespace n2 at level debug and all other namespaces (* ) at level fatal |
datal | error:n1,n2 | Logs n1 at level error , n2 at level fatal . All other namespaces will NOT get logged |
Examples
Run the server.js example with different settings:
No output
$ node examples/server.js
Logging .info and .error
$ DEBUG_LEVEL=info node examples/server.js
Logging .error for server only
$ DEBUG_LEVEL=error DEBUG=server node examples/server.js
Logging .error in production mode (JSON without colors)
$ NODE_ENV=production DEBUG_LEVEL=error node examples/server.js
Behavior is as with debug.
$ DEBUG=server,client:A node examples/server.js
Log server
at level info
, and all other modules at level error
$ DEBUG=info:server,error:* node examples/server.js
Settings
Environment Variables
Common
Setting | Values | Description
---- | ---- | ----
DEBUG | | Enables/disables specific debugging namespaces
DEBUG_LEVEL | error, warn, info, debug | sets debug level
DEBUG_COLORS | true/false | display colors (if supported)
Node only
Setting | Values | NODE_ENV=
development
| Description
---- | ---- | ---- | ----
DEBUG_JSON | true/false | false | use JSON format instead of string based log
DEBUG_SERVERINFO | true/false | false | adds server information like pid
and hostname
DEBUG_HIDE_DATE | true/false | false | hides date from log output default false
For NODE_ENV !== 'development'
the default logging is in JSON format using serverinfo and date.
Browsers only
Setting | Values | Description
---- | ---- | ----
DEBUG_URL | URL | log in JSON format to server (needs middleware.js
at the server side)
In the browser localStorage
is used to set/save the settings.
E.g. to enable level ERROR an all namespaces type in console and refresh your page/ app:
localStorage.DEBUG_LEVEL='error'
localStorage.DEBUG='*'
Options
You may set the global log options with:
examples/options.js
const fs = require('fs')
const Log = require('@lskjs/log')
const stream = fs.createWriteStream('./my.log')
Log.options({
level: 'DEBUG',
json: true,
serverinfo: true,
hideDate: false,
colors: false,
stream
})
const log = new Log('*')
log.debug({object: 1})
Option name | Setting | env | Type | Description
----- | ---- | ---- | ---- | ----
level | DEBUG_LEVEL | both | String |
namespaces | DEBUG | both | String |
json | DEBUG_JSON | node | Boolean |
spaces | DEBUG_SPACES | node | Number | JSON spaces
hideDate | DEBUG_HIDE_DATE | both | Boolean |
colors | DEBUG_COLORS | both | Boolean |
stream | -- | node | Stream | output stream (defaults to process.stderr
)
url | DEBUG_URL | browser | String |
formatters | -- | both | Object | custom formatters
Levels
(From bunyan)
fatal
: The service/app is going to stop or becomes unusable.
An operator should definitely look into this soon.error
: Fatal for a particular request, but the service/app continues servicing.
An operator should look at this soon(ish)warn
: A note on something that should probably be looked at by an operator eventually.info
: Detail on regular operation.debug
: Anything else, i.e. too verbose to be included in INFO
level.trace
: Anything else, i.e. too verbose to be included in INFO
level.
Namespaces
Namespaces select dedicated packages for logging (check Conventions)
considering the level selected with DEBUG_LEVEL
. To choose a different log-level
prefix the namespace with the level to be set for that namespace.
E.g. to log all packages on level FATAL
, test
on ERROR
, log:A
on WARN
. As a side-effect *
will also cause all modules using debug being logged.
$ DEBUG_LEVEL=fatal DEBUG=ERROR:test,WARN:log:A,* node examples/levels.js
ERROR test Error: boom
FATAL test fatal test +7ms
WARN log:A huh {"ghost":"rider"} +0ms
ERROR log:A Error: baam
FATAL log:A fatal A +1ms
FATAL log:B fatal B +0ms
using-debug using debug +0ms
using-debug:A using debug - feature A +1ms
So maybe consider using DEBUG=...,FATAL:*
instead:
$ DEBUG=error:test,warn:log:A,fatal:*,using-debug:* node examples/levels.js
ERROR test Error: boom
FATAL test fatal test +7ms
WARN log:A huh {"ghost":"rider"} +0ms
ERROR log:A Error: baam
FATAL log:A fatal A +1ms
FATAL log:B fatal B +0ms
using-debug:A using debug - feature A +1ms
Conventions
(from debug)
If you're using this in one or more of your libraries, you should use the name of
your library so that developers may toggle debugging as desired without guessing
names. If you have more than one debuggers you should prefix them with your
package name and use ":" to separate features. For example bodyParser
from
Connect would then be connect:bodyParser
. If you append a *
to the end of
your name, it will always be enabled regardless of the setting of the DEBUG
environment variable. You can then use it for normal output as well as debug output.
Wildcards
(from debug)
The *
character may be used as a wildcard. Suppose for example your library
has debuggers named connect:bodyParser
, connect:compress
, connect:session
,
instead of listing all three with DEBUG=connect:bodyParser,connect:compress,connect:session
,
you may simply do DEBUG=connect:*
, or to run everything using this module
simply use DEBUG=*
.
You can also exclude specific debuggers by prefixing them with a -
character.
For example, DEBUG=*,-connect:*
would include all debuggers except those starting with connect:
.
Output
@lskjs/log
supports two types of outputs
- human readable - this pretty much follows the output of debug
This is the default for
NODE_ENV=development
. Can be forced using DEBUG_JSON=0
- machine readable - JSON output (similar to bunyan)
This is the default for test/production envs. Can be forced using
DEBUG_JSON=1
JSON output
When using %j
, %o
, %O
all will expand to %j
JSON, so there is no difference when using in node.
Nonetheless it is not recommended to use these formatters for logging errors and objects as this complicates later log inspection.
Each log records into a single JSON stringified line.
Core fields are:
level
: One of the five log levels.name
: The name of the namespace logged.msg
: A message which should give reason for logging the line.hostname
: Hostname of the server. (Requires option serverinfo)pid
: PID of the logged process. (Requires option serverinfo).time
: Timestamp (Suppress with option hideDate).diff
: Difftime in milliseconds.
See examples/jsonOutput.js.
When logging a message string, number or a formatted string it will show up under msg
like:
log.debug('a %s, a number %d, an %o and %j', 'string', 1.2, {object: 1}, {NOT: 'RECOMMENDED'})
{ "level": "DEBUG",
"name": "package:feature",
"msg": "a string, a number 1.2, an {\"object\":1} and {\"NOT\":\"RECOMMENDED\"}",
"hostname": "server",
"pid": 8310,
"time": "2017-11-08T21:01:00.025Z",
"diff": 5
}
Objects without formatters get assigned, arrays will show up under arr
:
log.info({object: 1}, {json: true}, [1, 2, 3], '%s #%d', 'message', 1)
{ "level": "INFO",
"name": "package:feature",
"msg": "message #1"
"object": 1,
"json": true,
"arr": [1,2,3],
"time": "2017-11-09T21:09:49.482Z",
"diff": 0
}
An error gets logged under err
const err = new TypeError('bam')
err.status = 500
log.error(err, {object: 1})
{ "level":"ERROR",
"name":"package:feature",
"msg":"bam",
"err": {
"name":"TypeError",
"stack":"Error: bam\n at Object.<anonymous> (...\n at bootstrap_node.js:608:3",
"status": 500
},
"object": 1,
"time":"2017-11-09T21:16:16.764Z",
"diff":0
}
Custom formatters
You may use custom formatters e.g. to display numbers converted into hex-format.
examples/customFormatters.js
const Log = require('..')
Log.options({level: 'debug'})
const log = new Log('test', {formatters: {
h: (n) => `x${n.toString(16).toUpperCase()}`
}})
log.debug('%h', 255)
toJSON
If logging an object you may define a toJSON()
function on that object to change proper logging of the object itself:
examples/toJSON.js
const Log = require('@lskjs/log')
const log = new Log('*')
function reqToJSON () {
const {ip, method, url} = this
return {ip, method, url}
}
const req = {
method: 'GET', url: '/path', ip: '10.10.10.10',
headers: {'user-agent': 'Custom/2.0'}, connection: {}
}
req.toJSON = reqToJSON.bind(req)
log.debug({req: req})
Logging Browser messages
To log debug messages from the browser on your server you can enable a logger middleware in your express/ connect server.
const app = require('express')()
const {logger} = require('@lskjs/log')
app.use('./@lskjs/log', logger({maxSize: 100}))
...
In your single page application use:
import Log from '@lskjs/log'
localStorage.setItem('DEBUG_URL', '/api/log')
localStorage.setItem('DEBUG', 'myApp*')
const log = new Log('myApp')
log.debug('my first %s', 'logline')
Check example at examples/app
. To run it use:
DEBUG=* node examples/app/server.js
and open http://localhost:3000
References
Inspired by
📖 License
This project is licensed under the MIT License - see the LICENSE file for details
👥 Contributors
👏 Contributing
- Fork it (https://github.com/yourname/yourproject/fork)
- Create your feature branch (
git checkout -b features/fooBar
) - Commit your changes (
git commit -am 'feat(image): Add some fooBar'
) - Push to the branch (
git push origin feature/fooBar
) - Create a new Pull Request
📮 Any questions? Always welcome :)