Lambda wrapper @linzjs/lambda

$3

- Automatically chooses the correct HTTP output event format based on input event (API Gateway, ALB, FunctionURL or Cloudfront)
- Generates a request id for every request using a ULID
- Automatically Logs the correlationId if one is provided to the function.
- Logs a meta log at the end of the request @type: "report"
- Tracks performance and logs request duration & metrics using @linzjs/metrics

Why?

This repository wraps the default lambda handler so it can be invoked by ALB, API Gateway or Cloudfront without requiring code changes, while also apply a opinionated set of lambda defaults

#### Http

``typescript
import { lf, LambdaHttpResponse } from '@linzjs/lambda';

// This works for Cloudfront, FunctionURL, ALB or API Gateway events
export const handler = lf.http();

handler.router.get('/v1/ping', () => new LambdaHttpResponse(200, 'Ok'));
handler.router.get<{ Params: { style: string } }>(
'/v1/style/:style.json',
(req) => new LambdaHttpResponse(200, 'Style: ' + req.params.style),
);

// Handle all requests
handler.router.get('*', () => new LambdaHttpResponse(404, 'Not found'));

// create middleware to validate api key on all requests
handler.router.hook('request', (req) => {
const isApiValid = validateApiKey(req.query.get('api'));
// Bail early
if (!isApiValid) return new LambdaHttpResponse(400, 'Invalid api key');

// Continue
return;
});
`

#### Lambda

`typescript
import { lf } from '@linzjs/lambda';

export const handler = lf.handler(async (req) => {
if (req.event.Records.length === 0) throw new Error('No records provided');
for (const evt of req.event.Records) {
req.log.info({ key: evt.key }, 'Request s3');
}
});
`

$3

A ULID is generated for every request and can be accessed at req.id

every log message generated by req.log will by include the request id.

$3

Simple timing events can be tracked with timer see @linzjs/metrics

`typescript
req.timer.start('some:event');
// Do Work
const duration = req.timer.end('some:event');
`

TODO: this should eventually be replaced by open telemetry spans

$3

At the end of every request a metalog is logged with use information for monitoring and alerting in something like elasticsearch, to add additional keys to the metatalog use req.set()

`typescript
req.set('xyz', { x, y, z });
req.set('location', { lat, lon });
`

$3

Automatically includes a configured pino logger

`typescript
function doRequest(req) {
req.log.info('Some Log line'); // Includes useful information like requestId
}
`

This can be overridden at either the wrapper

`typescript
export const handler = lf.wrap(doRequest, myOwnLogger);
`

of set a different default logger

`typescript
lf.logger = myOwnLogger;
export const handler = lf.wrap(doRequest);
``