----- Original Message -----
Does this mean we will be able to move the hooks to the engine side at some point? That would be much better than needing it on VDSM.
Well, it sounds feasible to provide a hooking mechanism that enables to alter the domain XML in the engine, at some point. I'm not sure though that it could actually replace the hooks in VDSM since: 1. The XML won't be complete (host-specific configuration will be missing). 2. If the user wants to do some operation on the host with the hook, he'll need to send a request from the engine to the host, which is more complicated.
Yaniv Dary Technical Product Manager Red Hat Israel Ltd. 34 Jerusalem Road Building A, 4th floor Ra'anana, Israel 4350109
Tel : +972 (9) 7692306 8272306 Email: ydary@redhat.com IRC : ydary
On Wed, Nov 23, 2016 at 6:12 PM, Arik Hadas <ahadas@redhat.com> wrote:
----- Original Message -----
Hi,
Arik there is also custom metadata section for MOM and QoS in the libvirt domain XML and those values are now created as XML and later manipulated using libvirt API. VDSM will still need to know at least some basic stuff about the XML to be able to process it correctly (the metadata descriptor and the structure for example).
Besides the parsing of the devices that we would love to get rid of, I believe the parsing of Libvirt XML done by VDSM would remain as is.
Will the engine assume anything about the XML post-migration (for example to speed-up restarts for highly available VMs)? Because the hooks can change it significantly. Start hooks will be used anyway, but migration hook changes might not be reflected during the restart.
Not sure that I fully understand. You have a VM with configuration conf1 running on host1. While being migrated to host2 the configuration is changed to conf2. Do you suggest that the next time the VM restarts it would be created based on conf2?
Changes in the devices would be reflected on the next run (assuming the engine got the updated devices) - as today. Other than the devices, no configuration that is used on VM creation (static data) is read back by the engine so if it is changed it won't be reflected. And at the moment we have no plan to change the content of the data that is passed between the engine and VDSM, only its representation.
Btw, I'm taking back my statement about migration: "5. Not to re-generate the XML on each rerun attempt of VM run/migration." VM migration flow is irrelevant since the engine doesn't pass the VM configuration. It will remain as-is.
Martin
On Wed, Nov 23, 2016 at 1:59 PM, Arik Hadas <ahadas@redhat.com> wrote:
Hi All,
We are working on something that is expected to have a big impact,
this heads-up. First, we want you to be aware of this change and provide your feedback to make it as good as possible. Second, until the proposed mechanism is fully merged there will be a chase to cover all features unless new features are also implemented with the new mechanism. So please, if you are working on something that adds/changes something in the Libvirt's domain xml, do it with this new mechanism as well (first version would be merged soon).
* Goal Creating Libvirt XML in the engine rather than in VDSM. ** Today's flow Engine: VM business entity -> VM properties map VDSM: VM properties map -> Libvirt XML ** Desired flow Engine: VM business entity -> Libvirt XML
* Potential Benefits 1. Reduce the number of conversions from 2 to 1, reducing chances for mistakes in the process. 2. Reduce the amount of code in VDSM. 3. Make VM related changes easier - today many of these changes need to be reviewed in 2 projects, this will eliminate the one that tends to take longer. 4. Prevent shortcuts in the form of VDSM-only changes that should be better reflected in the engine. 5. Not to re-generate the XML on each rerun attempt of VM run/migration. 6. Future - not to re-generate the XML on each attempt to auto-start HA VM when using vm-leases (need to make sure we're using the up-to-date VM configuration though). 7. We already found improvements and cleanups that could be made while touching this area (e.g., remove the boot order from devices in the database).
* Challenges 1. Not to move host-specific information to the engine. For example,
hence path
to storage domain or sockets of channels. The solution is to use place-holders that will be replaced by VDSM. 2. Backward compatibility. 3. The more challenging part is the other direction - that will be the next phase.
* Status As a first step, we began with producing the Libvirt XML in the engine by converting the VM properties map to XML in the engine [1] And using the XML that is received as an input in VDSM [2]
[1] https://gerrit.ovirt.org/#/c/64473/ [2] https://gerrit.ovirt.org/#/c/65182/
Regards, Arik _______________________________________________ Devel mailing list Devel@ovirt.org http://lists.ovirt.org/mailman/listinfo/devel
_______________________________________________ Devel mailing list Devel@ovirt.org http://lists.ovirt.org/mailman/listinfo/devel