Only one instance of a DHCP agent is run per network

Bug #1174132 reported by Robert Collins on 2013-04-29
8
This bug affects 1 person
Affects Status Importance Assigned to Milestone
neutron
Undecided
Gary Kotton
tripleo
Medium
Ryan O'Hara

Bug Description

DHCP Agent's are stateless and can run HA, but the scheduler only schedules one instance - when a network node fails (or is rebooted / has maintenance done on it) this results in user visible downtime.

See also bug 1174591 which talks about the administrative overhead of dealing with failed nodes.

Robert Collins (lifeless) wrote :

https://etherpad.openstack.org/HavanaBareMetalVLAN was the summit discussion about this.

Changed in tripleo:
status: New → Triaged
importance: Undecided → High
Gary Kotton (garyk) wrote :

Hi,
By default the scheduler allocates one agent. You are then able to add additional ones.
Please see the example below:

openstack@openstack:~/devstack$ quantum dhcp-agent-list-hosting-net private
+--------------------------------------+----------------------------------+----------------+-------+
| id | host | admin_state_up | alive |
+--------------------------------------+----------------------------------+----------------+-------+
| f10e63e1-ea10-4897-adc3-7c395b7bbb20 | openstack.eng.lab.tlv.redhat.com | True | :-) |
+--------------------------------------+----------------------------------+----------------+-------+
openstack@openstack:~/devstack$ quantum agent-list
+--------------------------------------+--------------------+-----------------------------------------+-------+----------------+
| id | agent_type | host | alive | admin_state_up |
+--------------------------------------+--------------------+-----------------------------------------+-------+----------------+
| 18cf3f85-3879-497c-833e-0a5bfea38e71 | Open vSwitch agent | openstack.eng.lab.tlv.redhat.com | :-) | True |
| dcc13a1d-9d3c-4b06-ae4c-2263ece97a59 | L3 agent | openstack.eng.lab.tlv.redhat.com | :-) | True |
| dd1a8201-9f24-4b59-be67-310668a6030d | DHCP agent | gkotton-ubuntu12.eng.lab.tlv.redhat.com | :-) | True |
| f10e63e1-ea10-4897-adc3-7c395b7bbb20 | DHCP agent | openstack.eng.lab.tlv.redhat.com | :-) | True |
+--------------------------------------+--------------------+-----------------------------------------+-------+----------------+
openstack@openstack:~/devstack$ quantum dhcp-agent-network-add dd1a8201-9f24-4b59-be67-310668a6030d f10e63e1-ea10-4897-adc3-7c395b7bbb20
Unable to find network with name 'f10e63e1-ea10-4897-adc3-7c395b7bbb20'
openstack@openstack:~/devstack$ quantum dhcp-agent-network-add dd1a8201-9f24-4b59-be67-310668a6030d private
Added network private to DHCP agent
openstack@openstack:~/devstack$ quantum dhcp-agent-list-hosting-net private
+--------------------------------------+-----------------------------------------+----------------+-------+
| id | host | admin_state_up | alive |
+--------------------------------------+-----------------------------------------+----------------+-------+
| dd1a8201-9f24-4b59-be67-310668a6030d | gkotton-ubuntu12.eng.lab.tlv.redhat.com | True | :-) |
| f10e63e1-ea10-4897-adc3-7c395b7bbb20 | openstack.eng.lab.tlv.redhat.com | True | :-) |
+--------------------------------------+-----------------------------------------+----------------+-------+

Does this suffice?

Changed in quantum:
status: New → Opinion
Gary Kotton (garyk) on 2013-04-29
Changed in quantum:
status: Opinion → Confirmed
description: updated

Fix proposed to branch: master
Review: https://review.openstack.org/27907

Changed in quantum:
assignee: nobody → Gary Kotton (garyk)
status: Confirmed → In Progress
Gary Kotton (garyk) on 2013-05-15
Changed in quantum:
milestone: none → havana-1

Reviewed: https://review.openstack.org/27907
Committed: http://github.com/openstack/quantum/commit/c95e58b70796eae6bbc8bac283f81df9aa1d1894
Submitter: Jenkins
Branch: master

commit c95e58b70796eae6bbc8bac283f81df9aa1d1894
Author: Gary Kotton <email address hidden>
Date: Wed May 1 12:54:11 2013 +0000

    Enable network to be scheduled to N DHCP agents

    Fixes bug 1174132

    Change-Id: Iabe96fd8a98f3539eb21268fb5ef58df8dbd8782

Changed in quantum:
status: In Progress → Fix Committed
Robert Collins (lifeless) wrote :

Wooo! Thanks.

We need to fold this into the tripleO automation to close the tripleo task.

Thierry Carrez (ttx) on 2013-05-29
Changed in quantum:
status: Fix Committed → Fix Released
Robert Collins (lifeless) wrote :

From a tripleo perspective we just need to set 235 # dhcp_agents_per_network = 2 (or three) now.

tags: added: grizzly-backport-potential
Changed in tripleo:
importance: High → Medium
Thierry Carrez (ttx) on 2013-10-17
Changed in neutron:
milestone: havana-1 → 2013.2
Ryan O'Hara (rohara) on 2014-02-13
Changed in tripleo:
assignee: nobody → Ryan O'Hara (rohara)

Fix proposed to branch: master
Review: https://review.openstack.org/74424

Changed in tripleo:
status: Triaged → In Progress

Reviewed: https://review.openstack.org/74424
Committed: https://git.openstack.org/cgit/openstack/tripleo-image-elements/commit/?id=6dd529e01a5bb0df3be4ce518f25968fe8ed416f
Submitter: Jenkins
Branch: master

commit 6dd529e01a5bb0df3be4ce518f25968fe8ed416f
Author: Ryan O'Hara <email address hidden>
Date: Tue Feb 18 10:07:42 2014 -0600

    Update neutron config to use multiple dhcp agents

    Neutron should schedule two dhcp agents per network by default.

    Change-Id: I9775937cc54864fcc1cb95e3015d702b68131830
    Partial-Bug: #1174132

Alan Pevec (apevec) on 2014-03-31
tags: removed: grizzly-backport-potential
Dan Prince (dan-prince) on 2014-03-31
Changed in tripleo:
status: In Progress → Fix Committed
Changed in tripleo:
status: Fix Committed → Fix Released
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