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Builtin module REQuire Durations

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# breqd

**B**uiltin modules **REQ**uire **D**urations

This library measures the duration of `require()` on Node.js' builtin modules.

## Usage

### CLI usage

```js
$ npx breqd
...
  { moduleName: 'tty', duration: 3822 },
  { moduleName: 'diagnostics_channel', duration: 3410 },
  { moduleName: 'url', duration: 3151 }
]
File generated by breqd: breqd-node-v20.17.0-darwin-x64.json
Open it on https://ui.perfetto.dev!
```

Opening the generated file on <https://ui.perfetto.dev> looks like this.

![](https://raw.githubusercontent.com/RaisinTen/breqd/main/breqd.png)

### Programmatic usage

```ts
import {
  ModuleDurationsMap,
  ModuleDuration,
  getModuleDurations,
  sortModuleDurations,
} from 'breqd';

const moduleDurations: ModuleDurationsMap = getModuleDurations();

const sortedModuleDurations: ModuleDuration[] = sortModuleDurations(moduleDurations);

console.log(sortedModuleDurations);
// [
//   { moduleName: 'repl', duration: 4989944 },
//   { moduleName: 'assert', duration: 3411434 },
//   { moduleName: 'http2', duration: 2925764 },
//   ...
// ]
```

## API

### `getModuleDurations()`

- Returns `ModuleDurationsMap`:
  - `index` (**string**) - The module name.
  - value (**number**) - The duration of `require()` on the module in nanoseconds.

Measures the duration of `require()` on all builtin modules of the running Node.js process and returns it.

### `sortModuleDurations()`

- `moduleDurations` (**ModuleDurationsMap**) - The module-duration object from `getModuleDurations()`.
- Returns `ModuleDuration[]`:
  - `moduleName` (**string**) - The module name.
  - `duration` (**number**) - The duration of `require()` on the module in nanoseconds.

Returns a sorted array of all the builtin module `require()` durations in descending order of durations.

### `convertModuleDurationstoTEF()`

- `moduleDurations` (**ModuleDuration[]**) - The module-duration object from `sortModuleDurations()`.
- Returns `TEF[]`:
  - `name` (**string**) - The builtin module name.
  - `cat` (**string**) - The event category.
  - `ph` (**string**) - The event type.
  - `pid` (**number**) - The process ID.
  - `ts` (**number**) - The tracing clock timestamp of the event.
  - `dur` (**number**) - The duration of `require()` on the module in microseconds.

Converts the sorted array of all the builtin module `require()` durations into Chrome's [Trace Event Format](https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview#heading=h.yr4qxyxotyw), so that it can be viewed on <https://ui.perfetto.dev>.

## Why does it matter?

It matters if you care about startup performance, like in your Electron app where you might be `require()`-ing a number of Node.js modules during startup. For example:

The [`https-proxy-agent`](https://www.npmjs.com/package/https-proxy-agent) module has over 65M weekly downloads and it takes ~75ms to `require()` v7.0.5 on my Intel macOS Sonoma 14.6.1 running Node.js v20.17.0. ~43ms, i.e., 57% of the total module loading time is spent in requiring just Node.js' own builtin modules! Wouldn't it be great to see this get improved?

![](https://raw.githubusercontent.com/RaisinTen/breqd/main/https-proxy-agent.png)

The visualization has been generated by using the [perftrace](https://github.com/RaisinTen/perftrace) project.

## License

[MIT](LICENSE)

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