Writing a Backend¶
What is a backend¶
A backend is simply a store for objects. It needs to support four operations:
- Saving Python objects associated with a key (a key is a string)
- Loading Python objects by their key
- Create a lock (identified by a key)
- Release a lock (identified by a key)
There are a few other operations, like deleting an entry, that are useful, but not strictly necessary.
Backends are identified by a URI type string, generically called
For example, to connect to a redis backend, use
Your backend should support a similar scheme.
How to write a backend¶
You can start with the file
jug/backends/base.py which provides a
template with documentation. Implement the functions in there.
This module details all the operations that are necessary to implement a jug backend.
It can be used as a starting point (template) for writing new backends.
Mark a task as failed. Should have no effect if the task isn’t locked
- failed : bool
Whether the task was marked as failed
Try to atomically create a lock
- locked : bool
Whether the lock was created
Returns whether this task is marked as failed.
This code is not race-condition free. It may happen that by the time this function returns, the failed lock has been released.
- failed : boolean
Returns whether a lock exists for name. Note that the answer can be invalid by the time this function returns. Only by trying to acquire the lock can you avoid race-conditions. See the get() function.
This function is provided only because it might be possible to have a fast check before calling the expensive locking operation.
- locked : boolean