Lambda wrapper @linzjs/lambda

A minimal lambda wrapper for LINZ Javascript lambda function development

• 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

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

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

export const handler = lf.handler<S3Event>(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');
  }
});

Request ID generation

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.

Metrics

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

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

TODO: this should eventually be replaced by open telemetry spans

Metalog

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()

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

Pino logging

Automatically includes a configured pino logger

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

This can be overridden at either the wrapper

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

of set a different default logger

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