Public bug reported:
Related bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166197
NOTE: Config option "router_distributed" must be False.
This issue is happening when initially we have a
"max_l3_agents_per_router" number, we create a router and then we reduce
the redundancy.
For example, if "max_l3_agents_per_router=3" and we create a HA router. Neutron
will create 3 instances of this router and will create the corresponding
"routerl3agentbindings" registers. E.g.:
MariaDB [ovs_neutron]> select * from routerl3agentbindings;
+--------------------------------------+--------------------------------------+---------------+
| router_id | l3_agent_id |
binding_index |
+--------------------------------------+--------------------------------------+---------------+
| f8d3fec5-4648-48e9-b546-94f2e135df77 | 5c54529e-1f4e-4332-9674-96a1d15a16b2 |
1 |
| f8d3fec5-4648-48e9-b546-94f2e135df77 | 8112e03e-9191-495d-aea2-d2d7cd621767 |
2 |
| f8d3fec5-4648-48e9-b546-94f2e135df77 | 850beebc-3144-4673-a4cc-142162dba436 |
3 |
+--------------------------------------+--------------------------------------+---------------+
Now we reduce the redundancy to "max_l3_agents_per_router=1". If we remove the
agent assignation for those registers with "binding_index" different to 1, the
next time the router is updated, the L3 scheduler will create a new assignation
with "binding_index=1". When the router is updated (a subnet is added or
removed, a FIP is assigned or removed, etc), the scheduler is called. This
method [1] will determine what is the next index that needs to be created (that
is used both for the DHCP scheduler and the L3 scheduler).
In the given example, if the agents with "binding_index" different from 1 are
removed, the vacant binding index method [1] will return 1:
open_slots = sorted(list(all_indicies - set(binding_indices)))
--> all_indicies = {1}
--> binding_indices = {3} # for example
--> open_slots = {1} # instead of an empty set(), as expected here.
[1]https://github.com/openstack/neutron/blob/7c3d6c414d3c0f085cae94b6f2186c4415a9298b/neutron/scheduler/base_scheduler.py#L102-L107
** Affects: neutron
Importance: Medium
Assignee: Rodolfo Alonso (rodolfo-alonso-hernandez)
Status: New
** Changed in: neutron
Assignee: (unassigned) => Rodolfo Alonso (rodolfo-alonso-hernandez)
** Changed in: neutron
Importance: Undecided => Medium
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https://bugs.launchpad.net/bugs/2006496
Title:
[L3-HA] "max_l3_agents_per_router" not honored when the redundancy is
reduced
Status in neutron:
New
Bug description:
Related bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166197
NOTE: Config option "router_distributed" must be False.
This issue is happening when initially we have a
"max_l3_agents_per_router" number, we create a router and then we
reduce the redundancy.
For example, if "max_l3_agents_per_router=3" and we create a HA router.
Neutron will create 3 instances of this router and will create the
corresponding "routerl3agentbindings" registers. E.g.:
MariaDB [ovs_neutron]> select * from routerl3agentbindings;
+--------------------------------------+--------------------------------------+---------------+
| router_id | l3_agent_id
| binding_index |
+--------------------------------------+--------------------------------------+---------------+
| f8d3fec5-4648-48e9-b546-94f2e135df77 | 5c54529e-1f4e-4332-9674-96a1d15a16b2
| 1 |
| f8d3fec5-4648-48e9-b546-94f2e135df77 | 8112e03e-9191-495d-aea2-d2d7cd621767
| 2 |
| f8d3fec5-4648-48e9-b546-94f2e135df77 | 850beebc-3144-4673-a4cc-142162dba436
| 3 |
+--------------------------------------+--------------------------------------+---------------+
Now we reduce the redundancy to "max_l3_agents_per_router=1". If we remove
the agent assignation for those registers with "binding_index" different to 1,
the next time the router is updated, the L3 scheduler will create a new
assignation with "binding_index=1". When the router is updated (a subnet is
added or removed, a FIP is assigned or removed, etc), the scheduler is called.
This method [1] will determine what is the next index that needs to be created
(that is used both for the DHCP scheduler and the L3 scheduler).
In the given example, if the agents with "binding_index" different from 1 are
removed, the vacant binding index method [1] will return 1:
open_slots = sorted(list(all_indicies - set(binding_indices)))
--> all_indicies = {1}
--> binding_indices = {3} # for example
--> open_slots = {1} # instead of an empty set(), as expected here.
[1]https://github.com/openstack/neutron/blob/7c3d6c414d3c0f085cae94b6f2186c4415a9298b/neutron/scheduler/base_scheduler.py#L102-L107
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