Adding a custom tag to a Sentry event

chris48s

2023-05-29

Sentry allows you to enrich captured events by applying custom tags and attributes. I was recently working on a python application where I needed a re-usable abstraction to express the logic "if function X throws exception Y then apply this custom key=value tag when we log the exception to Sentry" in a bunch of places. Here's what I came up with:

from functools import wraps
from sentry_sdk import capture_exception, push_scope

def tag_error(exc_class, key, value):
    def decorator(fn):
        @wraps(fn)
        def wrapper(*args, **kwargs):
            try:
                return fn(*args, **kwargs)
            except (KeyboardInterrupt, SystemExit):
                raise
            except Exception as err:
                if isinstance(err, exc_class):
                    with push_scope() as scope:
                        scope.set_tag(key, value)
                        capture_exception(err)
                raise
        return wrapper
    return decorator

This gives us a @tag_error decorator, which can be applied to any function. For example:

@tag_error(ValueError, "custom-key", "custom-value")
def do_a_thing():
    ...
    raise ValueError("Oh no. A terrible thing has happened.")
    ...

This will tag any ValueErrors raised by calling do_a_thing() with custom-key=custom-value when we log the exception to sentry.