Re: [openstack-dev] [neutron] multiple agents with segment access

[Legacy, Allain]

> -Original Message-
> From: Ihar Hrachyshka [mailto:ihrac...@redhat.com]
> Sent: Tuesday, November 14, 2017 4:19 PM
> To: OpenStack Development Mailing List (not for usage questions)
> Subject: Re: [openstack-dev] [neutron] multiple agents with segment access
> 
> In general, you should be able to run both regular l2 agent (ovs) and sriov
> agent. If you have problems with it, we should probably assume it's a bug.
> Please report.


Ok, since this affects two distinct parts of the system I created 2 separate 
bug reports:

https://bugs.launchpad.net/neutron/+bug/1732445
https://bugs.launchpad.net/neutron/+bug/1732448
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Re: [openstack-dev] [neutron] multiple agents with segment access

[Ihar Hrachyshka]

In general, you should be able to run both regular l2 agent (ovs) and
sriov agent. If you have problems with it, we should probably assume
it's a bug. Please report.

On Tue, Nov 14, 2017 at 8:02 AM, Legacy, Allain
 wrote:
> Is it a known limitation that the ML2 plugin and associated drivers do not 
> properly handle cases where there are multiple agents running on the same 
> host?   That is, two or more agents that reside on the same host and both 
> report device/interface mappings  for physical networks?One such setup is 
> a set of nodes that are both running an L2 agent and a NIC SRIOV agent.
>
> We have found two problems specific to this configuration and are wondering 
> if these are known limitations, or simply not supported.
>
> For example, in a configuration where a host has L2, DHCP, and SRIOV agents 
> running on it, then:
>
> 1)   The DHCP scheduler can schedule a network to be hosted by that DHCP 
> agent even if the physical network is only supported by the SRIOV agent and 
> not by the L2 agent.  This can end up isolating the DHCP server as it will 
> not have access to the underlying physical segment.   This is happening 
> because "filter_hosts_with_network_access" in the Ml2Plugin will include the 
> host because the SRIOV mech driver reports that it has access to that segment.
>
> 2)   The Segment Plugin "segmenthostmappings" table gets overwritten with 
> tuples for whichever agent reports in last.  For example, if the L2 agent has 
> physical network mappings for 2 different physical networks (physnet0, 
> physnet1), but the SRIOV NIC agent only has 1 physical network reported 
> (physnet2), the segmenthostmappings table will have data for only physnet2 if 
> the SRIOV NIC agent reported last, or data for only both physnet0 and 
> physnet1 if the L2 agent reported last.  Data for physical networks belonging 
> to the other agent will be erroneously removed as stale entries.
>
> If it has been discussed before is there a plan to address this type of 
> configuration?
>
> Regards.
> Allain
>
>
>
> Allain Legacy, Software Developer, Wind River
> direct 613.270.2279  fax 613.492.7870 skype allain.legacy
> 350 Terry Fox Drive, Suite 200, Ottawa, Ontario, K2K 2W5
>
>
>
>
>
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