Error: No valid host was found

When launching an instance, I sometimes get an error “No valid host was found. Exceeded max scheduling attempts …” How do I resolve this?

Sometimes this error can be due to exceeding a quota. For example, if we check the logs on the hypervisor for this error, we might see

PortLimitExceeded: Maximum number of ports exceeded

To resolve this problem, you can increase the quota by running the command

neutron quota-update --tenant-id [TENANT-ID] --port 200

If that doesn’t work, https://bugs.launchpad.net/nova/+bug/1247844 might apply, and you may need to delete any instances with conflicting fixed IP addresses.

When resizing an instance, I get an error “No valid host was found. No valid host found for resize …” How do I resolve this?

This can happen for several different reasons, but if you ask our support team to check the logs and we find a “Filter AvailabilityZoneFilter returned 0 hosts” error in the nova-scheduler log, this can occasionally be due to a mismatch between the availability zone reported by nova and the availability zone listed in the database. This can be resolved on our end by having one of our engineers run a command similar to the following:

mysql> update instances set availability_zone="compute_enterprise" where uuid="8e53979f-76d8-47cf-ba9d-e6c594112683";