DHCP timeout when creating instances for specific tenants

Grant Morley grant at civo.com
Wed Dec 4 23:53:17 UTC 2019

HI Eric,

We are indeed already setting the DNS servers explicitly in the subnet 
so I don't think that is the issue ( from what I can tell ) I was 
wondering if it could be an issue with Neutron not responding in time 
for the DHCP request from the instance, however I haven't yet found any 
evidence of this.

The only other thought I had was that it could be an issue with RabbitMQ 
somehow and potentially increasing the "rpc timeout" on neutron to see 
if that helps as I have seen some errors stating that RabbitMQ didn't 
respond to a message request in time. However I think it could be a red 
herring as I would assume if RabbitMQ was to blame, existing tenants and 
instances would also be suffering.


On 04/12/2019 23:46, Eric K. Miller wrote:
> Hi Grant,
> I didn't see any DNS errors either.  The solution was to explicitly 
> configure the dns servers in the subnet.  Are you doing this already?  
> Or are you relying on the dnsmasq processes created for the router to 
> respond to DNS queries (and forward them respectively)?
> Eric
> *From:*Grant Morley [mailto:grant at civo.com]
> *Sent:* Wednesday, December 04, 2019 5:40 PM
> *To:* Eric K. Miller; openstack-operators at lists.openstack.org
> *Cc:* Ian Banks
> *Subject:* Re: DHCP timeout when creating instances for specific tenants
> Hi Eric,
> Thanks for getting back to me. I am fairly sure it is a DHCP error. 
> The instances are getting an IP when they eventually boot, it is just 
> taking a long time for them to bring up networking. The strange thing 
> is, it only seems to be new tenants. All existing tenants are 
> absolutely fine.
> I can check DNS as well just to be on the safe side, however I wasn't 
> seeing any errors in the Nova or Neutron logs when the instance(s) 
> were being created.
> Regards,
> On 04/12/2019 22:47, Eric K. Miller wrote:
>     Hi Grant,
>     Are you sure this is a DHCP timeout and not a DNS resolution
>     issue?  I ask because we have seen a strange DNS issue occur that
>     can cause something similar.
>     Are the VMs being assigned an IP after they finally boot?
>     Eric K. Miller
>     Genesis Hosting Solutions, LLC
>     Try our Genesis Public Cloud - powered by OpenStack!eut
>     https://genesishosting.com/
>     *From:*Grant Morley [mailto:grant at civo.com]
>     *Sent:* Wednesday, December 04, 2019 11:00 AM
>     *To:* openstack-operators at lists.openstack.org
>     <mailto:openstack-operators at lists.openstack.org>
>     *Cc:* Ian Banks
>     *Subject:* DHCP timeout when creating instances for specific tenants
>     Hi all,
>     I wonder if anyone can help shed any light on an odd issue we are
>     seeing with only a couple of specific tenants. Basically if they
>     launch an instance they are taking about 5 minutes to launch
>     rather than our usual 30 second or so launch.
>     We are seeing the following on the instance logs:
>     https://pastebin.com/hDstsd8G
>     Weirdly it only seems to be happening for 1 or 2 new tenants. I
>     have tested this on our personal account and a few other customers
>     have tested and their instances launch really quickly as expected.
>     Is there anything specific during the tenant creation that can
>     cause this issue? Or are there any logs in nova / neutron I should
>     be looking out for that might shed some light?
>     I haven't seen anything that is obvious. Any help would be much
>     appreciated as we are a little stumped at the moment.
>     Many thanks,
>     -- 
>     Image removed by sender.
>     Grant Morley
>     Cloud Lead, Civo Ltd
>     www.civo.com <https://www.civo.com/>| Signup for an account!
>     <https://www.civo.com/signup>
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