[Impact]
When running the latest Neutron ML2 Arista plugin on Ubuntu 18.04 with Python 3.6 I get:
Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/networking_arista/ml2/arista_sync.py", line 255, in sync_loop
sync_required = self.wait_for_sync_required()
File "/usr/lib/python3/dist-packages/networking_arista/ml2/arista_sync.py", line 184, in wait_for_sync_required
return self.wait_for_mech_driver_update(timeout)
File "/usr/lib/python3/dist-packages/networking_arista/ml2/arista_sync.py", line 165, in wait_for_mech_driver_update
resource = self.provision_queue.get(timeout=timeout)
File "/usr/lib/python3.6/multiprocessing/queues.py", line 104, in get
if not self._poll(timeout):
File "/usr/lib/python3.6/multiprocessing/connection.py", line 257, in poll
return self._poll(timeout)
File "/usr/lib/python3.6/multiprocessing/connection.py", line 414, in _poll
r = wait([self], timeout)
File "/usr/lib/python3.6/multiprocessing/connection.py", line 903, in wait
with _WaitSelector() as selector:
File "/usr/lib/python3.6/selectors.py", line 348, in __init__
self._poll = select.poll()
AttributeError: module 'select' has no attribute 'poll'
This is because arista_sync.py imports eventlet, which removes poll() from select as it is considered "non-green", see https://github.com/eventlet/eventlet/issues/608 . However earlier in mechanism_arista.py multiprocessing was imported, which then adjusted its implementation based on the fact that hasattr(select, 'poll') was True at that time.
The first solution that comes to mind would be to import eventlet way earlier in the project, before any import to multiprocessing and selectors, see http://eventlet.net/doc/patching.html#monkeypatching-the-standard-library . But I couldn't find the perfect place for this.
A cleaner solution (validated locally) is to import eventlet.queue.Queue instead of multiprocessing.Queue as we use this queue only to synchronise with en eventlet.greenthread. See http://eventlet.net/doc/modules/queue.html . So basically:
--- a/networking_arista/ml2/mechanism_arista.py
+++ b/networking_arista/ml2/mechanism_arista.py
[...]
-from multiprocessing import Queue
+from eventlet.queue import Queue
I'll open a review. Thanks!
PS: I'm hitting this while extending the new OpenStack Neutron API Arista Plugin charm ( https://opendev.org/openstack/charm-neutron-api-plugin-arista ) in order to support the latest OpenStack releases.
[Test Case]
Within the project itself:
https://opendev.org/x/networking-arista/src/branch/master/networking_arista/tests/unit/ml2/test_arista_sync.py#L31 exercises the newly introduced imports.
Within a consuming project:
https://opendev.org/openstack/charm-neutron-api-plugin-arista/src/branch/master/src/tests/tests.yaml#L18 has this code imported by neutron and validates that neutron runs, behaves as expected and succeeds at communicating with an Arista eAPI by creating/deleting networks.
[Regression Potential]
A mistake in the touched code could lead to:
1. neutron-server failing to start if the newly introduced imports don't work.
2. neutron-server failing to communicate with an Arista eAPI if the monkey-patched multiprocessing.Queue doesn't behave as expected. Note that this problem is already there anyway and this is what we intend to fix here.
Fix proposed to branch: master
Review: https:/