Node.js module for native bindings to the dearly beloved systemd-journald.
This example will start an ExpressJS server. Open your browser and visit: http://localhost:3000/{a}/{b}
The server will return the result of a divided by b. You feel subversive and may want to try b equals zero?! ;)
// npm install express systemd-journald
const Journald = require('systemd-journald');
const app = require('express')();
// This creates a new logging instance. The stated object defines default
// journal fields attached to every logging entry. syslog_identifier is the
// name displayed along with the log lines.
const log = new Journald({syslog_identifier: 'awesome-divide'});
app.get('/:a/:b', (req, res) => {
try {
// Convert numbers
let a = parseInt(req.params.a);
let b = parseInt(req.params.b);
// Divide a by b
let q = a / b;
// Throw an error if the result is not a number
// Funny side fact: In the first place I checked:
// if( typeof q != 'number' ) ...
// Well, this was not working. Infinity is recognised as 'number' and, you
// might already guessed it, NaN as well! Javascript as we know and love it.
if(isNaN(q) || q === Infinity ) throw new Error('No number!');
// Send the result to the client
res.end(q.toString());
// Log this request with priority 7
log.debug('Just answered a request', {
'dividend' : a,
'divisor' : b,
'quotient' : q,
'remote_addr': req.connection.remoteAddress
});
// Are you interested in the requests of a specific IP? Try:
// $ journalctl -t awesome-divide REMOTE_ADDR={IP}
// As you can see, you have to enter the field names in capital letters.
} catch(e) {
// The user screwed up! This will write the error message and stack trace to
// the journal with priority 3. Checkout your journal:
// $ journalctl -t awesome-divide -p 3 -o json-pretty
log.err(e);
res.status(400).end(e.message);
}
});
app.listen(3000);Debian-flavoured Linux distributions:
sudo apt-get install build-essential \
pkg-config \
libsystemd-devRHEL 7 flavoured Linux distributions:
sudo yum install gcc gcc-c++ make git \
systemd-develIn all cases, once the build dependencies are installed:
npm install systemd-journald --saveconst Journald = require( 'systemd-journald' );
const log = new Journald( defaultFields );
// Corresponding syslog level:
log.emerg( message, fields ); // - LOG_EMERG
log.alert( message, fields ); // - LOG_ALERT
log.crit( message, fields ); // - LOG_CRIT
log.err( message, fields ); // - LOG_ERR
log.warning( message, fields ); // - LOG_WARNING
log.notice( message, fields ); // - LOG_NOTICE
log.info( message, fields ); // - LOG_INFO
log.debug( message, fields ); // - LOG_DEBUGmessage: String or instance of Error.fields: Further key-value data attached to the journal. Nested objects will be also included in the journal. Keys will be converted to upper-case.{'obj': {'nested': 'Chuck Norris'}}will becomeOBJ_NESTED=Chuck Norris. Quite handy for filtering the journal.defaultFields: Fields attached to every entry. They may be overridden byfields.
Sepcial thanks to:
- ianare for improving compatibility with older systemd versions.
- jez9999 for making this module immune to future changes of syslog levels.
- Z3TA is responsible for
CODE_FILE,CODE_FUNCandCODE_LINEbeing settable by thefieldsparameter. - bryanburgers introduced the idea of default fields.
- spion for introducing compatibility with NodeJS 12 while preserving compatibility down to Node 0.10.
- GaikwadPratik for porting this module from NAN to Node-API.
I owe you a drink!
This module has been written after some unsuccessful attempts to get the module journald version 0.0.5 working under NodeJS 4.x / 5.x. Due to massive API changes of the v8 engine this module is fully broken from the point of view of recent NodeJS releases. So I rewrote it - this time with a little help of Native Abstractions for Node.js (nan). The nice guys from nan promised to ensure compatibility even on future API changes of v8. We will see ;)
Update: They've kept the promise - but we've changed to the on-board solution for native modules: Node-API. We hope to have even less problems with keeping this module compatible to NodeJS.
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