Suppressing the KeyError for an unbind() call

[anirvan-majumdar]

Hi,

This is a suggestion for possible improvement in the logic of invoking the unbind() method on the BoundLogger. We recently deployed structlog in our Django project. Everything seemed to work fine until we started getting a bunch of KeyErrors while unbinding parameters.

We realised that we had a recursive logic where on a child stack the context variable would get unbound and when the control came back to the parent stack, another call to unbind crashed the flow.

For now, we added a new wrapper class over the BoundLogger which simply suppresses the exception:

from structlog.stdlib import BoundLogger


class BoundLoggerWrapper(BoundLogger):
    def unbind(self, *keys):
        try:
            return super(BoundLoggerWrapper, self).unbind(*keys)
        except KeyError:
            return self.bind()

Just wanted to check whether doing this might have any unwanted consequences.

Thanks for this wonderful library!

[hynek]

I don’t think silencing errors is a good plan, but I may be open to add something like try_unbind?

---

Unrelatedly you mentioned you deployed structlog in a Django app…would you mind to contribute some wisdom how you did it? I haven’t used Django in years but people keep mentioning, that they’d like examples of that.

[anirvan-majumdar]

try_unbind would be perfect and clear in intent. The KeyError issue can be quite pervasive in a big application where binding/unbinding on the same key might happen within the context of a request/response cycle. Esp more so when a web application might also rely on an async library like celery 😕

would you mind to contribute some wisdom how you did it?

Sure thing. Would you like me to jot down some notes in the comments here or in a separate doc?

[hynek]

Sure thing. Would you like me to jot down some notes in the comments here or in a separate doc?

I think it would be the easiest for everybody if you just opened a bug “Add integration information for Django" and dump whatever you‘re comfortable to share there. Then we can start thinking how to structure it and where to put it!

[anirvan-majumdar]

Cool. Will do so by end of this week.

[hynek]

try_unbind() has been added in fd01af7 and will be released with 18.2.

[anirvan-majumdar]

Added a document here: #175