Lifecycle hooks

[ceilfors]

Recently I've got a use case of trying to execute something before a Lambda times out. This made me think of a lifecycle that I should have been able to listen to, for example, it may look like this:

laconia(app)
  .register(...)
  .on('30sBeforeTimeout', () => { /* do something * / })

Discussion

• Is this something that we should introduce?
• What other lifecycle hooks that developers may find useful here?
• Should the API be using .on(string)? I felt that a string makes it too easy for developers to have a typo. How might the API look like?

[hugosenari]

Maybe something like:

• 'error': to works like try/catch for unhandled errors;
• 'finally': to works like try/catch/finally;
• 'beforeHandle': to set adapters to event;

[ceilfors]

@hugosenari Thanks for joining this discussion! On try/catch or setting control flow, at the moment one of the philosophy I'm trying to encourage is use JavaScript as close as possible. Control flow like try/catch is a JavaScript syntax, I think a middleware can be introduced to tackle this. I think it's quite similar to beforeHandle for adapter, where high order function is used instead. What do you think?

[hugosenari]

Maybe we could implement everything as HOF adapter and see what makes sense move to core.

const myAdapter = hofAdapter({
  mappings: [getBody],
  onEnd: result => result,
  onSuccess: identity,
  throwMillisBeforeTimeout: 500,
  onError: error => { throw error; }
});

exports.handler = laconia(myAdapter(body => ({ data: body })));

Until we could do this:

module.exports = laconia(body => ({ data: body }))
  .on('end', () => {})
  .on('mapping', getBody)
  .on('success', result => result)
  .on('error', error => { throw error; )
  .on('beforeTimeout': timeroutErrorHandler);