Logging a future exception

log_future_exception.py

import tornado

from functools import wraps

def log_coroutine_exceptions(coro):
    """Coroutine (or any method that returns a future) decorator to log exceptions

    Example
    -------

    ::

    @log_coroutine_exceptions
    @tornado.gen.coroutine
    def raiser(self, arg):
        yield tornado.gen.moment
        raise Exception(arg)

    Assuming that your object (self) has a `log` attribute containing a logger instance

    """
    def log_cb(self, f):
        try:
            f.result()
        except Exception:
            self.log.exception('Unhandled exception calling coroutine {0!r}'
                               .format(coro))
    
    @wraps(coro)
    def wrapped_coro(self, *args, **kwargs):
        f = coro(self, *args, **kwargs)
        f.add_done_callback(partial(log_cb, self))
        return f

    return wrapped_coro