console.log in Node.js Azure Function does not output anywhere

[wpitallo]

How do we get console.log in a Node.js Azure function. I have been looking everywhere and cant seem to find out how to do this anywhere. I get that you can use context.log. But what if we need to log from dependencies etc. I really find it hard to believe that that console.log does not show up anywhere in a node.js azure function. Its a real deal breaker...

[sadranyi]

Aside the context, I believe you can instrument Application insights or some other 3rd party logging tools to to that. I personally use sentry.

[bnb]

You'll probably want to use context.log() – there's some more context here: https://docs.microsoft.com/en-us/azure/azure-functions/functions-reference-node#writing-trace-output-to-the-console

[BrianRosamilia]

This is possible with something like this @wpitallo

https://github.com/BrianRosamilia/azure-function-log-intercept/blob/master/index.js

If you're feeling adventurous you can try out the npm package I made to fix this https://www.npmjs.com/package/azure-function-log-intercept

It was frustrating my team as well.

[orvillelim]

+100

[nicholasdavidbrown]

Hi all, thanks @BrianRosamilia for the interceptor. It served me well for the past 12 months :) , however recently I've migrated the functions from V3 to V4.

I rewrote the log intercepter to use the new @azure/functions type like so:

import { InvocationContext } from "@azure/functions";

type LogMethod = 'log' | 'info' | 'warn' | 'error';

function interceptor(context: InvocationContext) {
    const methods = ['log', 'info', 'warn', 'error'];
    return methods.forEach((m: LogMethod) => higherOrderLog(m, context));
}

const higherOrderLog = (name: LogMethod, context: InvocationContext) => {
    const logFn = (...params: any[]) => {
        if (context[name]) {
            context[name](...params);
        }
        else if (context.log[name]) {
            // Must check context.log for some methods (currently warn, info, error)
            context.log[name](...params);
        }
    };

    console[name] = logFn;
};

export = interceptor;

It passes the tests. But when I use it, I get:

Warning: Unexpected call to 'log' on the context object after function execution has completed. Please check for asynchronous calls that are not awaited. Function name: {name}. Invocation Id: {id}.

I guess my question is, was there any fundamental changing to the logging between V3 and V4?

I'm not a huge fan of feeding the context through all of my functions if I can avoid it.

Thanks

[BrianRosamilia]

@nicholasdavidbrown Pretty slick code. Everyone using my library gets spammed by that and I don't think it actually changed between v3 and v4 as I've seen that message for years now.

Someone made a DefinitelyTyped definition for consuming my package, btw. Not sure if that would help your use case enough since you have added some nice typing to the core of my code.

I thought about overriding console.warn to just not output those messages. It's completely possible, but I didn't feel like playing whack-a-mole with the Microsoft warnings, but this might be a great use case for you since you are already hacking on what I started :D let me know if you have additional thoughts (but maybe move them to my repo so we don't notify everyone in this thread). It actually might make a great optional setting, a PR would be great but maybe I can work on it if you think its valuable enough.