Neutron attempts to schedule DHCP agents even when intentionally not in use

[Russell Bryant]

OVN has its own native support for DHCP, so the Neutron DHCP agent is not in use. When networks get created, we see warnings in the log about Neutron still trying to schedule DHCP agents.

We should be able to disable this code path completely when the DHCP agent is intentionally not in use.

2016-12-05 16:44:12.252 23149 WARNING neutron.scheduler.dhcp_agent_scheduler [req-038bedd2-fa56-4cfb-af68-8a36f39a2e9c 560fda6bf041441581ea756be353433c 21888697d4914989af439a25ebda0b76 - - -] No more DHCP agents
2016-12-05 16:44:12.253 23149 WARNING neutron.api.rpc.agentnotifiers.dhcp_rpc_agent_api [req-038bedd2-fa56-4cfb-af68-8a36f39a2e9c 560fda6bf041441581ea756be353433c 21888697d4914989af439a25ebda0b76 - - -] Unable to schedule network 45d29a60-a672-429f-b7d7-551ee985c8ca: no agents available; will retry on subsequent port and subnet creation events.

[Oleg Bondarev (obondarev)]

Possible workaround: get core plugin instance from ovn driver and set plugin.network_scheduler to None

[Pranab (pranabboruah)]

Unable to spend time on this. Sorry.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/693645

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/693645
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=139b496ef957364caee6861fd16676cdfb76a38b
Submitter: Zuul
Branch: master

commit 139b496ef957364caee6861fd16676cdfb76a38b
Author: Reedip <email address hidden>
Date: Mon Nov 11 10:54:42 2019 +0900

    Dont schedule Network, respecting network_auto_schedule config

    Currently, if dhcp mapping from a network is removed, it is reassigned
    to the network. This is because of the Network Scheduler's schedule
    function, which considers balancing the networks with the agents, whether
    enable_dhcp is set on its subnets or not. It does not take into account
    the network_auto_schedule config option. This is particularly disturbing
    when considering backends which have their provide their own DHCP.

    With this patch, if network_auto_schedule is set to False, networks wont
    be automatically scheduled to DHCP Agents. If DHCP is to be mapped to a
    network, it can be mapped using the CLI itself.

    While it may seem that this change is breaking what is already working,
    but as mentioned earlier, if there are network backends which provide DHCP
    support themselves, they wont need the automatic mapping, which the term
    "network_auto_schedule" actually stands for.

    Closes-Bug: #1647421
    Change-Id: If1a6a2a174d0f737415efa2abce518722316a77b

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 16.0.0.0b1 development milestone.