decorators.py

from functools import WRAPPER_ASSIGNMENTS, wraps

from .jobs import FunctionJob


def cacheback(
    lifetime=None,
    fetch_on_miss=None,
    cache_alias=None,
    job_class=None,
    task_options=None,
    **job_class_kwargs
):
    """
    Decorate function to cache its return value.

    :lifetime: How long to cache items for
    :fetch_on_miss: Whether to perform a synchronous fetch when no cached
                    result is found
    :cache_alias: The Django cache alias to store the result into.
    :job_class: The class to use for running the cache refresh job.  Defaults
                using the FunctionJob.
    :job_class_kwargs: Any extra kwargs to pass to job_class constructor.
                       Useful with custom job_class implementations.
    """
    if job_class is None:
        job_class = FunctionJob
    job = job_class(
        lifetime=lifetime,
        fetch_on_miss=fetch_on_miss,
        cache_alias=cache_alias,
        task_options=task_options,
        **job_class_kwargs
    )

    def _wrapper(fn):
        # using available_attrs to work around http://bugs.python.org/issue3445
        @wraps(fn, assigned=WRAPPER_ASSIGNMENTS)
        def __wrapper(*args, **kwargs):
            return job.get(fn, *args, **kwargs)

        # Assign reference to unwrapped function so that we can access it
        # later without descending into infinite regress.
        __wrapper.fn = fn
        # Assign reference to job so we can use the full Job API
        __wrapper.job = job
        return __wrapper

    return _wrapper