deleted_ports memory leak in dhcp agent

[Allain Legacy]

The "deleted_ports" member variable in the DHCP NetworkCache [1] can potentially leak memory. As ports are deleted uuid values are added to this set but they are never removed. If ports are continuously added and deleted on a network this set will grow unbounded.

[1] neutron.agent.dhcp.agent.NetworkCache.deleted_ports

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/521035

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/521035
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=5754f00ea8734a894e0c7963d46244ba7dc0dbe7
Submitter: Zuul
Branch: master

commit 5754f00ea8734a894e0c7963d46244ba7dc0dbe7
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Tue Jun 25 12:10:44 2019 +0000

    [DHCP] Implement an aging method for deleted_ports

    When a port is deleted, is added to the NetworkCache instance
    as a "deleted port". This set of ports is used by the DHCP agent
    to mark out as "stalled" any message received with this port
    in the payload.

    Eventually, each deleted port should be dropped from this set
    depending on when was deleted. A timeout of 1 day has been defined
    in this patch to drop any older deleted port.

    A "loopingcall.FixedIntervalLoopingCall" executes the deleted port
    cleanup, with an execution interval of 1 day too.

    Co-Authored-By: Rodolfo Alonso Hernandez <email address hidden>
    Partial-Bug: #1732458

    Change-Id: I0bca03a67e8b0ff8f508cf59383340a13724e51c