Expose this library as a pino mixin

simoneb commented 3 years ago

Thanks for this package. In reference to https://github.com/pinojs/pino/issues/648, I was thinking that a more robust way to expose this functionality might be to take a composition over inheritance^1 approach.

Instead of wrapping pino and use this library as a drop-in replacement, you could simply expose the mixin instead, so a user could compose it with pino.

The API would look something like:

import pino from 'pino';
import pinoLambda from 'pino-lambda';

async function handler(event, context) {
  const logger = pino({
    mixin: pinoLambda(event, context)
  });

  logger.info({ data: 'Some data' }, 'A log message');
}

In this way this package would become part of the pino ecosystem instead of being a replacement for pino.

What do you think?

carbonrobot commented 3 years ago

That was the original design, but pino mixins do not allow you to alter the formatting of the final output that is written to stdout. So although we could mixin the data from the request, we could not change the log format to the one required by Cloudwatch

simoneb commented 3 years ago

Interesting, then it's definitely something we need to look into on the pino side. I'll get back to you about this, thanks!

Eomm commented 3 years ago

I think we could find a good balance to do it using the default Pino apis.

Here is a quick&dirty example using:

pino mixin
within pino destination https://github.com/pinojs/pino/blob/master/docs/api.md#destination

The pino transport would be the best fit (the JSON.parse can be skipped), but I don't know if it works as expected on the Lambda environment

'use strict'

const pino = require('pino')
const { Transform, Writable } = require('stream')

const cloudwatchWritable = new Writable({
  defaultEncoding: 'utf8',
  write(chunk, encoding, callback) {
    const obj = JSON.parse(chunk)
    const time = new Date().toISOString();
    console.log(`${time}\t${obj.awsRequestId}\t${obj.msg}`)
    callback()
  }
})

let n = 0
const logger = pino({
  mixin() {
    return { awsRequestId: ++n }
  }
}, cloudwatchWritable)
logger.info('hello')
// 2021-10-21T16:46:49.985Z        1       hello

simoneb commented 2 years ago

@carbonrobot what do you think of @Eomm's proposed approach? Would you be interested in turning this library into something that could be plugged into pino instead of replacing it? We can help out on this. As an alternative, we may create a different library, but we'd prefer to avoid duplicated efforts.

carbonrobot commented 2 years ago

@simoneb I will begin testing this today for a new version

simoneb commented 2 years ago