https://github.com/clinicjs/notare-monitor

https://github.com/clinicjs/notare-monitor

Last synced: 2 months ago
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• Host: GitHub
• URL: https://github.com/clinicjs/notare-monitor
• Owner: clinicjs
• License: other
• Created: 2020-05-11T20:17:30.000Z (over 4 years ago)
• Default Branch: main
• Last Pushed: 2020-11-24T20:47:54.000Z (about 4 years ago)
• Last Synced: 2024-10-22T22:50:07.198Z (3 months ago)
• Language: TypeScript
• Size: 38.1 KB
• Stars: 5
• Watchers: 3
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Contributing: CONTRIBUTING.md
  • License: LICENSE
  • Code of conduct: CODE_OF_CONDUCT.md

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README

        
# notare-monitor -- Node.js observer

Extracted from the `notare` module, `notare-monitor` provides

a Node.js streams `Readable` that monitors and reports on

various Node.js performance metrics.

## Example

```js

const { Monitor } = require('notare-monitor');

const { pipeline, Writable } = require('stream');

class myWritable extends Writable {

  constructor() {

    super({ objectMode: true });

  }

  _write(chunk, encoding, callback) {

    console.log(JSON.stringify(chunk));

    callback();

  }

}

const monitor = new Monitor();

pipeline(monitor, new myWritable(), (err) => {

  if (err) {

    console.error('There was an error!');

    process.exit(1);

  }

});

```

## API

### Constructor:  `Monitor([options])`

Create a new `'Monitor` object.

* `options` (`object`)

  * `hz`: (`number`) An integer between 1 and 1000 that specifies the number

    of samples per second the `Monitor` should generate. The higher this

    number, the greater the performance impact the `Monitor` will have.

    The default is `2`. The `NOTARE_HZ` environment variable may also be

    used to set this value.

  * `handles`: (`boolean`) When true, the `Monitor` will track and report

    on the number of async resources in use by Node.js. Enabling this has

    a measurable performance impact on the Node.js process so it is off

    by default. Setting the `NOTARE_HANDLES` environment variable to `1`

    may also be used to set this value.

  * `gc`: (`boolean`) When true, the `Monitor` will track and report on

    garbage collection counts and durations. Enabling this has a

    measurable performance impact on the Node.js process so it is off

    by default. Setting the `NOTARE_GC` environment variable to `1`

    may also be used to set this value.

The `Monitor` object extends from Node.js [`stream.Readable`][].

## Configuration via Environment Variables

* `NOTARE_HZ=n` where `n` is the number of samples per second (default `2`)

* `NOTARE_HANDLES=1` instructs notare to monitor async hook handle counts

  (disabled by default)

* `NOTARE_GZ=1` instructs notare to monitor garbage collection (disabled

  by default)

[`stream.Readable`]: https://nodejs.org/dist/latest-v14.x/docs/api/stream.html#stream_readable_streams