Request-scoped logging

[macourteau]

Fastify includes a log member in the request, which makes it possible to output request-scoped logs. Specifically, the output logs include a reqId which is unique to every request, but consistent across all logs generated within the scope of a request, making it possible to better analyze logs later.

It would be very useful to be able to access this logger from within request handlers. I presume the logger could output non-request-scoped logs in other plugins if the system they integrate into doesn't have request-scoped logging (e.g. connect-express, AFAICT).

This would be useful in Connect for Node.js - I don't think it would apply to Connect for Web.

I have tried to capture the log member from the Fastify object and use it within request handlers, but the logs generated by that logger are not request-scoped.

[smaye81]

Hi @macourteau you can do this now using context. Take a look at #835 for an example of how to do it. Specifically this comment.

Let me know if that helps.

[macourteau]

Ah, yes, that absolutely works - thanks! I think it would be useful to add this to the documentation, perhaps in the Context section, or an "Advanced" section.

[smaye81]

Totally agree @macourteau . We are actually updating the docs to include this, they're just still in-flight. You can see the PR here.