Hello dev community. Recently I’ve faced following behaviour of virtual DNS in OpenContrail when using it with OpenStack deployment. During cold migration/resize procedure we are losing A-record and PTR-record for VM. Detailed steps are quite simple:
1: VM boot via nova. when new vif for VM is created agent sends dns requests to add A and PTR records for VM. 2: cold migration / resize operation. “new” VM with same name is booting on another compute node, but “old” vm is still present on original host with appropriate vif plugged into vrouter. Vif insertion for “new” VM causes agent to send requests to DNS for A and PTR records. However, requests looks same that was created for original VM since data, ttl, name, zone and type of record has not changed. DNS server just ignores this update. 3: confirmation of operation from step 2. Nova flushes original VM as well as VIF plugged to vrouter. Agent notifies DNS server with 2 delete requests - for A and PTR records respectively. Server handles requests correctly and removes records from table. “New” VM will have no appropriate DNS records. Appropriate bug is filed in Launchpad https://bugs.launchpad.net/opencontrail/+bug/1702856 This behaviour does not look correct, but due to architecture statement ( https://github.com/Juniper/contrail-controller/wiki/DNS-and-IPAM) that name of DNS record is actual name of VM server can’t handle this situation. So two questions are in my mind 1 - Is there any possibility to extend DNS record name in respect to “other” parameters in such way to avoid situation above? 2 - Is there any need to create additional handling for situation above? Since it’s pretty narrow case I wonder if it makes sense to add extensions to agent/server behaviour. Please feel free to add your comments here or in Launchpad. Any suggestions/help will be appreciated. Thanks. -- *Best Regards* *Sergey Matov* *Mirantis Inc*
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