Return the value in case of pickle serialization exception instead of failing the whole call

from dogpile.cache import make_region

TIMEOUT_SECONDS = 10 * 60


def my_key_generator(namespace, fn):
    fname = fn.__name__

    def generate_key(*arg):
        # generate a key template:
        # "fname_%d_arg1_arg2_arg3..."
        # key_template = fname + "_" + "%d" + "_".join(str(s) for s in arg[1:])
        key_template = fname + "_" + "_".join(str(s) for s in arg)

        return key_template

    return generate_key


region = make_region(function_key_generator=my_key_generator).configure(
    "dogpile.cache.redis",
    expiration_time=TIMEOUT_SECONDS,
    arguments={
        "host": "localhost",
        "port": 6379,
        "db": 0,
        "redis_expiration_time": TIMEOUT_SECONDS * 2,  # 2 hours
        "distributed_lock": True,
        # thread_local_lock – bool, whether a thread-local Redis lock object should be used.
        # This is the default, but is not compatible with asynchronous runners, as they run in
        # a different thread than the one used to create the lock.
        "thread_local_lock": False,
    },

)


@region.cache_on_arguments()
def load_user_info(user_id):
    log.info(f"Called func {user_id}")
    return lambda: user_id

print(load_user_info(1))

This returns the pickle error, which is to be expected.

Traceback (most recent call last):
  File "/Users/riyad/dev-src/chaos-theory/python-test/dogpile-test.py", line 120, in <module>
    print(load_user_info(1))
          ^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/decorator.py", line 232, in fun
    return caller(func, *(extras + args), **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/dogpile/cache/region.py", line 1577, in get_or_create_for_user_func
    return self.get_or_create(
           ^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/dogpile/cache/region.py", line 1042, in get_or_create
    with Lock(
  File "/opt/homebrew/lib/python3.11/site-packages/dogpile/lock.py", line 185, in __enter__
    return self._enter()
           ^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/dogpile/lock.py", line 94, in _enter
    generated = self._enter_create(value, createdtime)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/dogpile/lock.py", line 178, in _enter_create
    return self.creator()
           ^^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/dogpile/cache/region.py", line 1012, in gen_value
    self._set_cached_value_to_backend(key, value)
  File "/opt/homebrew/lib/python3.11/site-packages/dogpile/cache/region.py", line 1288, in _set_cached_value_to_backend
    key, self._serialized_cached_value(value)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/dogpile/cache/region.py", line 1258, in _serialized_cached_value
    return self._serialize_cached_value_elements(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/lib/python3.11/site-packages/dogpile/cache/region.py", line 1232, in _serialize_cached_value_elements
    serializer(payload),
    ^^^^^^^^^^^^^^^^^^^
AttributeError: Can't pickle local object 'load_user_info.<locals>.<lambda>'

My question is is there a way when an exception happens on the dogpile side catch the exception, log the exception and return the actual value instead of totally failing the call?

Start in dogpile/cache/region.py at get_or_create_for_user_func, _set_cached_value_to_backend, and _serialized_cached_value, which appear in the traceback. Reproduce the failure with the supplied Redis configuration and verify the chosen behavior for serialization exceptions, including logging and returning the uncached value. Add coverage for the failing callable case.