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logging library doesn't support Exceptions #172
Description
The logger in firebase_functions doesn't seem to provide reasonable support for exceptions.
In the example, firebase suggests extracting a portion of the error and including it:
try
...
except:
e = sys.exc_info()[0]
# Attach an error object as the second argument
logger.error("Unable to read quote from Firestore, sending default instead", error=e)
However this fails with an error:
../../../../Library/Caches/pypoetry/virtualenvs/oasis-zYbk3Ww0-py3.11/lib/python3.11/site-packages/firebase_functions/logger.py:130: in error
write(_entry_from_args(LogSeverity.ERROR, *args, **kwargs))
../../../../Library/Caches/pypoetry/virtualenvs/oasis-zYbk3Ww0-py3.11/lib/python3.11/site-packages/firebase_functions/logger.py:95: in write
print(_json.dumps(_remove_circular(entry)), file=write_file)
../../../../.pyenv/versions/3.11.7/lib/python3.11/json/__init__.py:231: in dumps
return _default_encoder.encode(obj)
../../../../.pyenv/versions/3.11.7/lib/python3.11/json/encoder.py:200: in encode
chunks = self.iterencode(o, _one_shot=True)
../../../../.pyenv/versions/3.11.7/lib/python3.11/json/encoder.py:258: in iterencode
return _iterencode(o, 0)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
self = <json.encoder.JSONEncoder object at 0x10166ee10>, o = <class 'TypeError'>
def default(self, o):
"""Implement this method in a subclass such that it returns
a serializable object for ``o``, or calls the base implementation
(to raise a ``TypeError``).
For example, to support arbitrary iterators, you could
implement default like this::
def default(self, o):
try:
iterable = iter(o)
except TypeError:
pass
else:
return list(iterable)
# Let the base class default method raise the TypeError
return JSONEncoder.default(self, o)
"""
> raise TypeError(f'Object of type {o.__class__.__name__} '
f'is not JSON serializable')
E TypeError: Object of type type is not JSON serializable
../../../../.pyenv/versions/3.11.7/lib/python3.11/json/encoder.py:180: TypeError
Moreover it's not really an ideal API to log a subset of an exception. Ideally the entire stack trace would be included.
If you instead simply print the error, you can see a reasonable stack trace in the logs for the function.
I'd expect the example to not throw. I'd also expect the logging API to explicitly support logging Exceptions with stack traces
Activity
mattprinold commentedon Mar 1, 2024
so i ran into this problem also. It seems that the logger is trying to serialize an exception which is not possible so you need to convert the exception to something that is serializable, like a string representation of the exception. Found this out thanks to this stackoverflow thread: https://stackoverflow.com/questions/68108446/typeerror-object-of-type-typeerror-is-not-json-serializable-python
This should resolve the problem:
logger.error("Unable to read quote from Firestore, sending default instead", error=str(e))You also shouldn't be using a bare except so for a better message use something like:
HassanBahati commentedon Dec 8, 2025
Hi @sjudd, thank you for reporting this issue. We have received it and we shall keep you posted on any developments. Cheers!
cabljac commentedon Jul 22, 2026
Going through the backlog of open issues. Confirmed the shape of this one:
logger.error(..., error=e)hitsTypeError: Object of type type is not JSON serializablebecause the entry goes straight through_json.dumps, and @mattprinold'sstr(e)workaround is the right stopgap (thanks for digging that up). The docs example throwing is the immediate bug; explicit exception support with stack traces is the better fix and we'll look at it as part of this pass.