koa-server-timing/README.md

Koa Server Timinig header generation middleware

# koa-server-timing

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 Koa 2 [`Server-Timing`](http://wicg.github.io/server-timing/) header middleware.

## Installation

```bash
$ npm install koa-server-timing
```

## API

```js
const Koa = require('koa');
const app = new Koa();
app.use(require('koa-server-timing')({ total: true /* default to NODE_ENV !== 'production' */ }));

ctx.state.timings.startSpan('A Task description', 'taskSlug' /* optional, will be created a-task-description, if missed */)

/* ... do some long task to measure here */
ctx.state.timings.stopSpan('A Task description' /* or 'taskSlug' or return from startSpan */);

```

### Options

* `total` where do you want to see total processing time in Server-Timings

## Example

```js
const timings = require('koa-server-timing');
const koa = require('koa');
const db = require('./mongoose');
const app = koa();

app.use(timings());

app.listen(3000);

console.log('listening on port 3000');

app.use(async (ctx, next) => {
    ctx.state.timings.startSpan('Query DB for User object');
    const user = await db.User.findOne({ email: 'test@test.com' }).exec();
    ctx.state.timings.stopSpan('Query DB for User object'); // or just pass return of startSpan (it will be a slug)
})

```

### Why

  - Small, no dependencies, 100% test coverage
  - Uses `process.hrtime`, so, no extra timers and very precise

### See also
  - See [`@thomasbrueggemann/node-servertiming`](https://github.com/thomasbrueggemann/node-servertiming) for non-Koa version that uses Timers

## License

  MIT

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