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60 lines
2.6 KiB
Markdown
60 lines
2.6 KiB
Markdown
# Log4js - Appenders
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Appenders serialise log events to some form of output. They can write to files, send emails, send data over the network. All appenders have a `type` which determines which appender gets used. For example:
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```javascript
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const log4js = require('log4js');
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log4js.configure({
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appenders: {
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out: { type: 'stdout' },
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app: { type: 'file', filename: 'application.log' }
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},
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categories: {
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default: { appenders: [ 'out', 'app' ], level: 'debug' }
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}
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});
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```
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This defines two appenders named 'out' and 'app'. 'out' uses the [stdout](stdout.md) appender which writes to standard out. 'app' uses the [file](file.md) appender, configured to write to 'application.log'.
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## Core Appenders
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The following appenders are included with log4js. Some require extra dependencies that are not included as part of log4js (the [smtp](smtp.md) appender needs [nodemailer](https://www.npmjs.org/packages/nodemailer) for example), and these will be noted in the docs for that appender. If you don't use those appenders, then you don't need the extra dependencies.
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* [categoryFilter](categoryFilter.md)
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* [console](console.md)
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* [dateFile](dateFile.md)
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* [file](file.md)
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* [fileSync](fileSync.md)
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* [gelf](gelf.md)
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* [hipchat](hipchat.md)
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* [logFaces-HTTP](logFaces-HTTP.md)
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* [logFaces-UDP](logFaces-UDP.md)
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* [loggly](loggly.md)
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* [logLevelFilter](logLevelFilter.md)
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* [logstashUDP](logstashUDP.md)
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* [mailgun](mailgun.md)
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* [multiFile](multiFile.md)
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* [multiprocess](multiprocess.md)
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* [recording](recording.md)
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* [redis](redis.md)
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* [slack](slack.md)
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* [smtp](smtp.md)
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* [stderr](stderr.md)
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* [stdout](stdout.md)
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## Other Appenders
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Log4js can load appenders from outside the core appenders. The `type` config value is used as a require path if no matching appender can be found. For example, the following configuration will attempt to load an appender from the module 'cheese/appender', passing the rest of the config for the appender to that module:
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```javascript
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log4js.configure({
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appenders: { gouda: { type: 'cheese/appender', flavour: 'tasty' } },
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categories: { default: { appenders: ['gouda'], level: 'debug' }}
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});
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```
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Log4js checks the following places (in this order) for appenders based on the type value:
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1. The core appenders: `require('./appenders/' + type)`
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2. node_modules: `require(type)`
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3. relative to the main file of your application: `require(path.dirname(require.main.filename) + '/' + type)`
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4. relative to the process' current working directory: `require(process.cwd() + '/' + type)`
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If you want to write your own appender, read the [documentation](writing-appenders.md) first.
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