Environment

Djangae contains a small collection of utility functions which are useful on App Engine.

Retry

This is a helper for calling functions which may intermittently throw errors. It is useful for things such as performing Datastore transactions which may collide, or calling other APIs which may occasionally fail but that should succeed on a subsequent attempt.

djangae.utils.retry

retry(function, _catch=None, _attempts=3, _initial_wait=375, _max_wait=30000)

Calls the given function, catching the given exception(s), and (re)trying up to a maximum of _attempts times. If the intial call fails, it will wait _initial_wait milliseconds before making the second attempt. The wait will double on each subsequent retry, up to a maximum of _max_wait milliseconds.

_catch defaults to:

(
    djangae.db.transaction.TransactionFailedError,
    google.appengine.api.datastore_errors.Error,
    google.appengine.runtime.apiproxy_errors.Error
)

djangae.utils.retry_on_error

A function decorator which routes the function through retry.

@retry_on_error(_catch=None, _attempts=3, _initial_wait=375, _max_wait=30000)
def my_function():
    ...

djangae.utils.retry_until_successful

retry(function, _catch=None, _attempts=∞, _initial_wait=375, _max_wait=30000)

The same as retry, but _attempts is unlimited, so it will keep on retrying until either it succeeds or you hit an uncaught exception, such as the App Engine DeadlineExceededError.