Add ability to format `debug` as JSON output

[gajus]

I'd like there to be an option (controllable using environment variables) that would make debug module print JSON output instead of plain text.

This at the moment can be achieved using a module such as debug-to-json (@ping yoshuawuyts). The problem with the pipe solution is that it is not always easy to modify the command used to start the program (e.g. How to append an argument to a container command?).

Maybe I am doing something wrong, but (in a large deployment) logs coming via debug are quite useless ("large deployment" being a Kubernetes cluster with filebeat + ELK used for logging). [I suppose it is possible to reconize debug output in logstash and convert it to JSON?]

Being able to configure debug output with environment variable would greatly alleviate the difficulty of log processing here, e.g.

DEBUG_FORMAT=json

The other thing to note here is that certain log aggregation methods (filebeat) require that logs come in one-per-line. Plain text output does not guarantee this; JSON can.

Furthermore, the JSON format could be used to supplement debug output with meta information such as package name, version. This can be a controllable option via environment variables too.

I'd be happy to raise a PR.

[thebigredgeek]

With v3, you'll be able to override the out function... which will allow you to format the log output however you want. v2 doesn't including functionality like this, though

[gajus]

Well, overriding the functionality of out is hardly a fix here. If I need to override something, I'd rather use a logging framework such as bunyan or winston. The convenience of debug is that it is a convention driven, runtime configurable logging tool. If I need to override something, then it is just another logging framework.

[thebigredgeek]

Well, a major goal of debug is to be minimal while also extensible. If you have a case where you need to write to a file, or write JSON to stdout, or move data to logstash via HTTP, debug should be able to support that without including the functionality into the core lib

[gajus]

debug should be able to support that without including the functionality into the core lib

How .. ?

[gajus]

The mere fact that the output can be multiline makes it impossible parse the logs in any reliable way.

[thebigredgeek]

Overwriting out, as I said before. You'll be able to stick whatever function you want on there, and do whatever you want with the output. It will be passed a string, which you parse into whatever form you want (JSON, etc) and then send wherever you want

[gajus]

Overwriting out, as I said before. You'll be able to stick whatever function you want on there, and do whatever you want with the output. It will be passed a string, which you parse into whatever form you want (JSON, etc) and then send wherever you want

That requires to have access to the debug instance. It is fine if my application and ALL of the dependencies share the same version of debug. However, if at least one of them does not, there is no way for me to control output format of that dependency from within my application.

[thebigredgeek]

I mean, by default, you aren't going to see any output if you are dealing with third-party libs. If you care about the output from third-party libs, and want a special format, it doesn't seem like a stretch to require you to install debug as a dep and overwrite the log function

[gajus]

This is year 2020.

• I have an application lalaland that uses debug@v4.
• lalaland dependency awesomestdlib uses debug@3.

How do I format logs of awesomestdlib using the proposed out property override?

[gajus]

If you really want to depend on overriding the output method, then use a global variable, e.g.

// debug-format.js
global.visionmediaDebugOut = () => {};

Then whatever app that wants to override the out method would need to include this script prior to executing any code, e.g. node -r debug-format.js my-app.js.

Unlike the proposed approach, this approach can be work with multiple versions of debug in a backwards compatible way.

I don't think thats a right approach. It is an overkill. Simply allowing to output content in JSON format using ENV as configuration would be enough.

[thebigredgeek]

Well, using an env variable is good and all, but it requires additional surface area for the lib.... yet another configuration option that has to be well supported on every single platform running debug (node, all major browsers, electron, cordova, etc).

[gajus]

another configuration option that has to be well supported on every single platform running debug (node, all major browsers, electron, cordova, etc).

Don't understand the argument. JSON.stringify is part of the ECMA standard since 1.7.

[thebigredgeek]

Standardized output to TTY and non-TTY interfaces on a variety of platforms with yet another output format isn't as simple as simply calling JSON.stringify