Hi, very first question which comes to mind is: will vdsm hooks which alter the libvirt xml still work? I believe this is a much used feature and if it would not work anymore out of the box this would be a huge pain in upgrading existing systems.

furthermore I don't really see the benfits when you generate the xml in engine: you still need to alter it in vdsm as you write, to fill in host specific things like storagepaths anyway, meaning you have to maintain twice the codebase _and_ coordinate between the two of them, so nothing goes wrong if one project changes something in the xml.

but this are just my 2 cent :-) -- Mit freundlichen Grüßen / Regards Sven Kieske Systemadministrator Mittwald CM Service GmbH & Co. KG Königsberger Straße 6 32339 Espelkamp T: +495772 293100 F: +495772 293333 https://www.mittwald.de Geschäftsführer: Robert Meyer St.Nr.: 331/5721/1033, USt-IdNr.: DE814773217, HRA 6640, AG Bad Oeynhausen Komplementärin: Robert Meyer Verwaltungs GmbH, HRB 13260, AG Bad Oeynhausen _______________________________________________ Devel mailing list Devel(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/devel

On Wed, Nov 23, 2016 at 2:59 PM, Arik Hadas <ahadas(a)redhat.com&gt; wrote: > Hi All, > > We are working on something that is expected to have a big impact, hence > 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, 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] Thanks for the heads up! How does this, if at all, affect: 1. vdsm hooks

2. The interaction of engine, hosted-engine HA agent, engine vm configuration saved in shared storage, etc.? Will this require a change in ha-agent and the saved configuration?

Best, > > > [1] https://gerrit.ovirt.org/#/c/64473/ > [2] https://gerrit.ovirt.org/#/c/65182/ > > Regards, > Arik > _______________________________________________ > Devel mailing list > Devel(a)ovirt.org > http://lists.ovirt.org/mailman/listinfo/devel -- Didi

Hi All, We are working on something that is expected to have a big impact, hence 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, 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(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/devel

----- 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(a)redhat.com&gt; wrote: > > Hi All, > > > > We are working on something that is expected to have a big impact, hence > > 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, 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(a)ovirt.org > > http://lists.ovirt.org/mailman/listinfo/devel >

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. 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(a)redhat.com IRC : ydary On Wed, Nov 23, 2016 at 6:12 PM, Arik Hadas <ahadas(a)redhat.com&gt; 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(a)redhat.com&gt; wrote: > > > Hi All, > > > > > > We are working on something that is expected to have a big impact, > hence > > > 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, > 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(a)ovirt.org > > > http://lists.ovirt.org/mailman/listinfo/devel > > > _______________________________________________ > Devel mailing list > Devel(a)ovirt.org > http://lists.ovirt.org/mailman/listinfo/devel > _______________________________________________ Devel mailing list Devel(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/devel

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.

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(a)redhat.com IRC : ydary On Wed, Nov 23, 2016 at 6:12 PM, Arik Hadas <ahadas(a)redhat.com&gt; 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(a)redhat.com&gt; wrote: > > > Hi All, > > > > > > We are working on something that is expected to have a big impact, > hence > > > 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, > 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(a)ovirt.org > > > http://lists.ovirt.org/mailman/listinfo/devel > > > _______________________________________________ > Devel mailing list > Devel(a)ovirt.org > http://lists.ovirt.org/mailman/listinfo/devel >

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. 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(a)redhat.com IRC : ydary On Wed, Nov 23, 2016 at 6:12 PM, Arik Hadas <ahadas(a)redhat.com&gt; 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(a)redhat.com&gt; wrote: > > > Hi All, > > > > > > We are working on something that is expected to have a big impact, > > > hence > > > 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, > > > 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(a)ovirt.org > > > http://lists.ovirt.org/mailman/listinfo/devel > > > _______________________________________________ > Devel mailing list > Devel(a)ovirt.org > http://lists.ovirt.org/mailman/listinfo/devel

Hi All, We are working on something that is expected to have a big impact, hence 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, 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/

----- Original Message ----- > On Wed, Nov 23, 2016 at 07:59:40AM -0500, Arik Hadas wrote: > > Hi All, > > > > We are working on something that is expected to have a big impact, hence > > 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, 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/ > > I should start by saying that I love libvirt's domxml standard. Unlike > Vdsm's API, it is a real *standard* for defining VMs. In this regards, > you are suggesting a positive step. > > However, Engine is much more complex than Vdsm. It is also our > single-point-of-failure, and where CPU is the most scarce. I am worried > that in the foreseeable future it would only make Engine bigger, without > reducing the size and complexity of Vdsm. > > Before taking this move, we must map what Vdsm does, because that logic > would have to be copied into Engine. Few things pop up to mind: > > - pci addresses. would Vdsm report back the libvirt-assigned addresses > in XML format, or would it keep parsing them? Ideally, VDSM will report back the devices in XML format. The engine will then add the unmanaged devices and update the pci addresses. Need to put some more thoughts into this, though. > > - hot plug. Device xml should be generated by Engine, much like in the > vm cteate flow Good point, I didn't think of hot plugs - right, they could be changed as well later on. > > - network rewiring. Vdsm uses the "dummy bridge" to implement a vNIC > that is connected no-where. Engine would need to care about what was > up until now a vdsm-side implementation detail. Right, I almost finished to copy the creation of the network interfaces to the engine. This knowledge that you refer to will only be in the module that creates the XML, it doesn't seem to be much of an issue. > > - storage path. this was mentioned above, but actually, the paths are > the same on all hosts. We inteded to have an abstraction layer there, > but we never ever used it. All volumes sit under > /rhev/data-center/poolID/domainID/imageID/volumeID > Basically, Engine can hard-code this in the domxml, and no one would > notice.

But I see that LUN and cinder disks are represented differently (not as PDIV) - I'll check this.

> > - OvS. Recently, we have changed how VMs can be connected to their > network. It is possible (albeit not recommended yet!) to connect a VM > to an OvS instead of Linux bridges. This is done without Engine really > caring, or knowing how the domxml is modified. Yeah, I saw that. The only complication I see at this point is that for OvS we create more elements than only the 'source' element. I believe that we could use a place-holder that contains the network name and replace it with the tags that are needed for SR-IOV, OvS and ordinary interfaces, no? This seems to be the only thing that is difficult to generate on the engine's side (related to the network interfaces). > > - minor tweaks. exposing a new feature into Engine's UI is hard. Over > the years, few tweaks have been pushed as custom properties. > there are not many (I see now only sndbuf, queues, viodiskcache, > vhost) but the implementation should make sure they are not forgotten. Sure. > > Maybe, Vdsm should consider Engine's domxml only as a "recomendation" > and modify it based on its hooks and custom properties. This can > surprise Engine, a defies the pupose of having xml-building logic moved > away from Vdsm. > _______________________________________________ Devel mailing list Devel(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/devel

----- Original Message ----- > On Tue, Nov 29, 2016 at 2:21 PM, Arik Hadas <ahadas(a)redhat.com&gt; wrote: > > > > > > ----- Original Message ----- > >> On Wed, Nov 23, 2016 at 07:59:40AM -0500, Arik Hadas wrote: > >> > Hi All, > >> > > >> > We are working on something that is expected to have a big impact, hence > >> > 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, > >> > 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/ > >> > >> I should start by saying that I love libvirt's domxml standard. Unlike > >> Vdsm's API, it is a real *standard* for defining VMs. In this regards, > >> you are suggesting a positive step. > >> > >> However, Engine is much more complex than Vdsm. It is also our > >> single-point-of-failure, and where CPU is the most scarce. I am worried > >> that in the foreseeable future it would only make Engine bigger, without > >> reducing the size and complexity of Vdsm. > >> > >> Before taking this move, we must map what Vdsm does, because that logic > >> would have to be copied into Engine. Few things pop up to mind: > >> > >> - pci addresses. would Vdsm report back the libvirt-assigned addresses > >> in XML format, or would it keep parsing them? > > > > Ideally, VDSM will report back the devices in XML format. > > The engine will then add the unmanaged devices and update the pci > > addresses. > > Need to put some more thoughts into this, though. > > > >> > >> - hot plug. Device xml should be generated by Engine, much like in the > >> vm cteate flow > > > > Good point, I didn't think of hot plugs - right, they could be changed as > > well later on. > > > >> > >> - network rewiring. Vdsm uses the "dummy bridge" to implement a vNIC > >> that is connected no-where. Engine would need to care about what was > >> up until now a vdsm-side implementation detail. > > > > Right, I almost finished to copy the creation of the network interfaces to > > the engine. > > This knowledge that you refer to will only be in the module that creates > > the XML, it doesn't seem to be much of an issue. > > > >> > >> - storage path. this was mentioned above, but actually, the paths are > >> the same on all hosts. We inteded to have an abstraction layer there, > >> but we never ever used it. All volumes sit under > >> /rhev/data-center/poolID/domainID/imageID/volumeID > >> Basically, Engine can hard-code this in the domxml, and no one would > >> notice. > > This is wrong, and engine cannot hard code this or anything else. > > Engine should can describe only what is knows about disks, only vdsm > can add the disk xml. Of course, the engine will describe only the information it knows, but that seems to be most of the disk's related data. Let's say that the engine is managed to generate something like: <disk type='file' device='disk' snapshot='no'>

<driver name='qemu' type='qcow2' cache='none'/> <source file='$PATH:PDIV or other representations$'/>

<target dev='hda' bus='ide'/> <serial>54-a672-23e5b495a9ea</serial> </disk>

(and similar structures for the other kind of disks). Then, VDSM can simply replace the placeholder $PATH...$ with the concrete path of the disk. For VDSM it would save a lot of code (most of the code in vdsm/virt/vmdevices/storage.py I suppose) What else doesn't the engine know? And couldn't this data be set by VDSM by replacing place-holders as in the example above? > > > > > But I see that LUN and cinder disks are represented differently (not as > > PDIV) - I'll check this. > > Of course, and even disks using DIV can modified in by vdsm, for > example glusterfs > using libgfapi. > > > > >> > >> - OvS. Recently, we have changed how VMs can be connected to their > >> network. It is possible (albeit not recommended yet!) to connect a VM > >> to an OvS instead of Linux bridges. This is done without Engine really > >> caring, or knowing how the domxml is modified. > > > > Yeah, I saw that. The only complication I see at this point is that for OvS > > we create more elements than only the 'source' element. > > I believe that we could use a place-holder that contains the network name > > and replace it with the tags that are needed for SR-IOV, OvS and ordinary > > interfaces, no? > > This seems to be the only thing that is difficult to generate on the > > engine's side (related to the network interfaces). > > > >> > >> - minor tweaks. exposing a new feature into Engine's UI is hard. Over > >> the years, few tweaks have been pushed as custom properties. > >> there are not many (I see now only sndbuf, queues, viodiskcache, > >> vhost) but the implementation should make sure they are not forgotten. > > > > Sure. > > > >> > >> Maybe, Vdsm should consider Engine's domxml only as a "recomendation" > >> and modify it based on its hooks and custom properties. This can > >> surprise Engine, a defies the pupose of having xml-building logic moved > >> away from Vdsm. > >> > > _______________________________________________ > > Devel mailing list > > Devel(a)ovirt.org > > http://lists.ovirt.org/mailman/listinfo/devel >

----- Original Message ----- > On Tue, Nov 29, 2016 at 4:30 PM, Arik Hadas <ahadas(a)redhat.com&gt; wrote: > > > > > > ----- Original Message ----- > >> On Tue, Nov 29, 2016 at 2:21 PM, Arik Hadas <ahadas(a)redhat.com&gt; wrote: > >> > > >> > > >> > ----- Original Message ----- > >> >> On Wed, Nov 23, 2016 at 07:59:40AM -0500, Arik Hadas wrote: > >> >> > Hi All, > >> >> > > >> >> > We are working on something that is expected to have a big impact, > >> >> > hence > >> >> > 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, > >> >> > 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/ > >> >> > >> >> I should start by saying that I love libvirt's domxml standard. Unlike > >> >> Vdsm's API, it is a real *standard* for defining VMs. In this regards, > >> >> you are suggesting a positive step. > >> >> > >> >> However, Engine is much more complex than Vdsm. It is also our > >> >> single-point-of-failure, and where CPU is the most scarce. I am worried > >> >> that in the foreseeable future it would only make Engine bigger, > >> >> without > >> >> reducing the size and complexity of Vdsm. > >> >> > >> >> Before taking this move, we must map what Vdsm does, because that logic > >> >> would have to be copied into Engine. Few things pop up to mind: > >> >> > >> >> - pci addresses. would Vdsm report back the libvirt-assigned addresses > >> >> in XML format, or would it keep parsing them? > >> > > >> > Ideally, VDSM will report back the devices in XML format. > >> > The engine will then add the unmanaged devices and update the pci > >> > addresses. > >> > Need to put some more thoughts into this, though. > >> > > >> >> > >> >> - hot plug. Device xml should be generated by Engine, much like in the > >> >> vm cteate flow > >> > > >> > Good point, I didn't think of hot plugs - right, they could be changed > >> > as > >> > well later on. > >> > > >> >> > >> >> - network rewiring. Vdsm uses the "dummy bridge" to implement a vNIC > >> >> that is connected no-where. Engine would need to care about what was > >> >> up until now a vdsm-side implementation detail. > >> > > >> > Right, I almost finished to copy the creation of the network interfaces > >> > to > >> > the engine. > >> > This knowledge that you refer to will only be in the module that creates > >> > the XML, it doesn't seem to be much of an issue. > >> > > >> >> > >> >> - storage path. this was mentioned above, but actually, the paths are > >> >> the same on all hosts. We inteded to have an abstraction layer there, > >> >> but we never ever used it. All volumes sit under > >> >> /rhev/data-center/poolID/domainID/imageID/volumeID > >> >> Basically, Engine can hard-code this in the domxml, and no one would > >> >> notice. > >> > >> This is wrong, and engine cannot hard code this or anything else. > >> > >> Engine should can describe only what is knows about disks, only vdsm > >> can add the disk xml. > > > > Of course, the engine will describe only the information it knows, but that > > seems to be most of the disk's related data. > > Let's say that the engine is managed to generate something like: > > <disk type='file' device='disk' snapshot='no'> > > file may be "block" or "network", in glusterfs engine may send "file" and > vdsm > will replace it to "network". Right right, that's what I meant by "and similar structures for the other kind of disks" - basically we'll move the same logic that determines this to the engine in order to produce the right elements. > > > <driver name='qemu' type='qcow2' cache='none'/> > > <source file='$PATH:PDIV or other representations$'/> > > file may need to be "dev" Same, we'll check the diskType in the engine in order to determine the right attributes.

> > > <target dev='hda' bus='ide'/> > > <serial>54-a672-23e5b495a9ea</serial> > > </disk> > > Basically you must inspect the code in vdsm to understand the difference > and what engine can do and cannot. > > Also, how will vdsm fix the xml without the pool, domin, image and volume > ids? > > How do you want to send them if we send xml? Note that the placeholder contains this information ($PATH:PDIV or other representations$)

It will be the engine's responsibility to provide all the data that VDSM needs in order to produce the right replacements within the placeholders > > > > > (and similar structures for the other kind of disks). > > > > Then, VDSM can simply replace the placeholder $PATH...$ with the concrete > > path of the disk. > > For VDSM it would save a lot of code (most of the code in > > vdsm/virt/vmdevices/storage.py I suppose) > > > > What else doesn't the engine know? And couldn't this data be set by VDSM by > > replacing place-holders as in the example above? > > > >> > >> > > >> > But I see that LUN and cinder disks are represented differently (not as > >> > PDIV) - I'll check this. > >> > >> Of course, and even disks using DIV can modified in by vdsm, for > >> example glusterfs > >> using libgfapi. > >> > >> > > >> >> > >> >> - OvS. Recently, we have changed how VMs can be connected to their > >> >> network. It is possible (albeit not recommended yet!) to connect a VM > >> >> to an OvS instead of Linux bridges. This is done without Engine > >> >> really > >> >> caring, or knowing how the domxml is modified. > >> > > >> > Yeah, I saw that. The only complication I see at this point is that for > >> > OvS > >> > we create more elements than only the 'source' element. > >> > I believe that we could use a place-holder that contains the network > >> > name > >> > and replace it with the tags that are needed for SR-IOV, OvS and > >> > ordinary > >> > interfaces, no? > >> > This seems to be the only thing that is difficult to generate on the > >> > engine's side (related to the network interfaces). > >> > > >> >> > >> >> - minor tweaks. exposing a new feature into Engine's UI is hard. Over > >> >> the years, few tweaks have been pushed as custom properties. > >> >> there are not many (I see now only sndbuf, queues, viodiskcache, > >> >> vhost) but the implementation should make sure they are not > >> >> forgotten. > >> > > >> > Sure. > >> > > >> >> > >> >> Maybe, Vdsm should consider Engine's domxml only as a "recomendation" > >> >> and modify it based on its hooks and custom properties. This can > >> >> surprise Engine, a defies the pupose of having xml-building logic moved > >> >> away from Vdsm. > >> >> > >> > _______________________________________________ > >> > Devel mailing list > >> > Devel(a)ovirt.org > >> > http://lists.ovirt.org/mailman/listinfo/devel > >> >

Hi All, We are working on something that is expected to have a big impact, hence 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, 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