Added TRACE level logging.

[loren-osborn]

This is just a rebased update to PR #652

Please see discussion and history there.

[loren-osborn]

Added tests from #643 as @stevvooe suggested in #652.

[loren-osborn]

Pulled in a few improvements from #810.

[loren-osborn]

@stevvooe, I saw your comment: containerd/containerd#2028

@Random-Liu I am a maintainer there...

I think the problem with #652 is that it is not backwards compatible for those using the interface to define a logger type. I'll LGTM it and see if that is a concern.

I understand your concern, but it rather makes me think we're using interfaces wrong. I think they should generally require the minimum functionality to accomplish what's required. All the logLevel methods are really convenience functions. Let me think on this a bit, but I think we can get a lot less repetitive code while making user-defined loggers much simpler and more adaptable.

The way StdLogger and FieldLogger are defined, they only make sense as a way to abstract logrus internal types. We could make implementing user-defined loggers dead simple, by adding a few interfaces and a bit of plumbing.

[loren-osborn]

@stevvooe I have some good ideas regarding interfaces for useful user-defined logging, but I think I will wait on implementation until this PR is merged in, so I don't have to make some of the changes twice.

@sirupsen, let me know if there are any additional blockers on reviewing and merging this PR, as it appears to have been kicking around in various forms for 2+ years now.

@drampull, @xandrewrampulla, @Random-Liu, @BenTheElder, @gonix, @Xiol, @chackett, @pasztorpisti, @dnephin, @mkorolyov, @dgsb, @dmathieu: All of your contributed code and/or comments on this issue. Do you have anything to add, or would you like to see any additions to this PR?

[gonix]

Looks good to me.

[Xiol]

Looks good to me too. Can't tell you how excited I am for this - can finally get rid of my trace level wrappers.

[dgsb]

Can you complete TestLogLevelEnabled with this new level ?

[dgsb]

@loren-osborn thank you for your contritbution, this looks mostly good to me, I've just requested a slight change in a test function.
We may also want to warn all hooks implementers of this new level before tagging this new version.
Even if it is a non-breaking api change it may have impact on how the hooks are implemented.

[loren-osborn]

@dgsb, Thanks for the quick feedback. I know everybody is eager to have this in a new release, but I have one more change in mind (that I mentioned above in my comment to @stevvooe ) after this is merged that would further extend Ext1FieldLogger, and I'd prefer not to add an additional Ext2FieldLogger for these new methods, so perhaps, after merging this into master, you could hold off on a release a few days until my next PR is ready?

[dgsb]

@loren-osborn, there is indeed no need to tag immediately a new version. I usually tag a new version at the beginning of the month.

[loren-osborn]

@dgsb, I expect to make that a separate PR, so feel free to merge this whenever convenient.

(You’ll probably also want to close #629, #643, #652, #663, and #810. It looks like you’ve closed several of these already.)

[loren-osborn]

I should probably amend the last commit message to

PR#844: Added Trace to TestLogLevelEnabled() (requested by @dgsb)

before you merge this branch, but I won’t be at a computer for another 3 hours.

I can do it then, or you’re welcome to amend the commit before then if you have time.

Thanks.

Update: Done.

[Dieterbe]

awesome. thank you so much. i've been wanting a trace level and now i have it :D 🎈

[loren-osborn]

@dgsb, Given all the legwork you're needing to do here, It's likely a good idea to add a way for a hook implementor to query the range of the log levels, so if it changes again, the hook developers don't need to make additional chanes?

[dgsb]

@loren-osborn we don't need an api for that, we already have the variable AllLevels which gathers all existing levels.
Anyhow, hooks implementors needs to be warned when we add a new level, especially ones with a high volume.

[loren-osborn]

Something like AllLevels is exactly what I had in mind. I’m sorry I hadn’t noticed it there before.