Re: [ovirt-devel] [vdsm] Engine XML: metadata and devices from XML

> On 16 Mar 2017, at 09:45, Francesco Romani <fromani(a)redhat.com&gt; wrote: > > We talked about sending storage device purely on metadata, letting Vdsm > rebuild them and getting the XML like today. > > In the other direction, Vdsm will pass through the XML (perhaps only > parts of it, e.g. the devices subtree) like before. > > This way we can minimize the changes we are uncertain of, and more > importantly, we can minimize the risky changes. > > > The following is a realistic example of how the XML could look like if > we send all but the storage devices. It is built using my pyxmlpickle > module (see [3] below). That’s quite verbose. How much work would it need to actually minimize it and turn it into something more simple. Most such stuff should go away and I believe it would be beneficial to make it difficult to use to discourage using metadata as a generic junkyard

> > <domain type='kvm' id='10'> > <name>a0</name> > <uuid>ccd945c8-8069-4f31-8471-bbb58e9dd6ea</uuid> > <metadata xmlns:ovirt-tune="http://ovirt.org/vm/tune/1.0" > xmlns:ovirt-vm="http://ovirt.org/vm/1.0" > xmlns:ovirt-instance="http://ovirt.org/vm/instance/1.0"> > <ovirt-tune:qos/> > <ovirt-vm:vm/> > <ovirt-instance:instance> > <ovirt-instance:value type="dict"> > <ovirt-instance:item key="devices" type="list"> > <ovirt-instance:item index="0" type="dict"> > <ovirt-instance:item key="index" > type="str">2</ovirt-instance:item> > <ovirt-instance:item key="iface" > type="str">ide</ovirt-instance:item> > <ovirt-instance:item key="specParams" type="dict"> > <ovirt-instance:item key="path" type="str"/> > </ovirt-instance:item> > <ovirt-instance:item key="readonly" > type="str">true</ovirt-instance:item> > <ovirt-instance:item key="deviceId" > type="str">e59c985c-46c2-4489-b355-a6f374125eb9</ovirt-instance:item> > <ovirt-instance:item key="address" type="dict"> > <ovirt-instance:item key="bus" > type="str">1</ovirt-instance:item> > <ovirt-instance:item key="controller" > type="str">0</ovirt-instance:item> > <ovirt-instance:item key="type" > type="str">drive</ovirt-instance:item> > <ovirt-instance:item key="target" > type="str">0</ovirt-instance:item> > <ovirt-instance:item key="unit" > type="str">0</ovirt-instance:item> > </ovirt-instance:item> > <ovirt-instance:item key="device" > type="str">cdrom</ovirt-instance:item> > <ovirt-instance:item key="shared" > type="str">false</ovirt-instance:item> > <ovirt-instance:item key="path" type="str"/> > <ovirt-instance:item key="type" > type="str">disk</ovirt-instance:item> > </ovirt-instance:item> > <ovirt-instance:item index="1" type="dict"> > <ovirt-instance:item key="poolID" > type="str">5890a292-0390-01d2-01ed-00000000029a</ovirt-instance:item> > <ovirt-instance:item key="volumeInfo" type="dict"> > <ovirt-instance:item key="domainID" > type="str">c578566d-bc61-420c-8f1e-8dfa0a18efd5</ovirt-instance:item> > <ovirt-instance:item key="volType" > type="str">path</ovirt-instance:item> > <ovirt-instance:item key="leaseOffset" > type="int">0</ovirt-instance:item> > <ovirt-instance:item key="path" > type="str">/rhev/data-center/mnt/192.168.1.20:_srv_virtstore_nfs_rel40x_data/c578566d-bc61-420c-8f1e-8dfa0a18efd5/images/66441539-f7ac-4946-8a25-75e422f939d4/5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc</ovirt-instance:item> > <ovirt-instance:item key="volumeID" > type="str">5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc</ovirt-instance:item> > <ovirt-instance:item key="leasePath" > type="str">/rhev/data-center/mnt/192.168.1.20:_srv_virtstore_nfs_rel40x_data/c578566d-bc61-420c-8f1e-8dfa0a18efd5/images/66441539-f7ac-4946-8a25-75e422f939d4/5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc.lease</ovirt-instance:item> > <ovirt-instance:item key="imageID" > type="str">66441539-f7ac-4946-8a25-75e422f939d4</ovirt-instance:item> > </ovirt-instance:item> > <ovirt-instance:item key="index" > type="int">0</ovirt-instance:item> > <ovirt-instance:item key="iface" > type="str">virtio</ovirt-instance:item> > <ovirt-instance:item key="apparentsize" > type="str">8589934592</ovirt-instance:item> > <ovirt-instance:item key="imageID" > type="str">66441539-f7ac-4946-8a25-75e422f939d4</ovirt-instance:item> > <ovirt-instance:item key="readonly" > type="str">false</ovirt-instance:item> > <ovirt-instance:item key="shared" > type="str">false</ovirt-instance:item> > <ovirt-instance:item key="truesize" > type="str">0</ovirt-instance:item> > <ovirt-instance:item key="type" > type="str">disk</ovirt-instance:item> > <ovirt-instance:item key="domainID" > type="str">c578566d-bc61-420c-8f1e-8dfa0a18efd5</ovirt-instance:item> > <ovirt-instance:item key="reqsize" > type="str">0</ovirt-instance:item> > <ovirt-instance:item key="format" > type="str">raw</ovirt-instance:item> > <ovirt-instance:item key="deviceId" > type="str">66441539-f7ac-4946-8a25-75e422f939d4</ovirt-instance:item> > <ovirt-instance:item key="address" type="dict"> > <ovirt-instance:item key="function" > type="str">0x0</ovirt-instance:item> > <ovirt-instance:item key="bus" > type="str">0x00</ovirt-instance:item> > <ovirt-instance:item key="domain" > type="str">0x0000</ovirt-instance:item> > <ovirt-instance:item key="type" > type="str">pci</ovirt-instance:item> > <ovirt-instance:item key="slot" > type="str">0x05</ovirt-instance:item> > </ovirt-instance:item> > <ovirt-instance:item key="device" > type="str">disk</ovirt-instance:item> > <ovirt-instance:item key="path" > type="str">/rhev/data-center/5890a292-0390-01d2-01ed-00000000029a/c578566d-bc61-420c-8f1e-8dfa0a18efd5/images/66441539-f7ac-4946-8a25-75e422f939d4/5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc</ovirt-instance:item> > <ovirt-instance:item key="propagateErrors" > type="str">off</ovirt-instance:item> > <ovirt-instance:item key="optional" > type="str">false</ovirt-instance:item> > <ovirt-instance:item key="bootOrder" > type="str">1</ovirt-instance:item> > <ovirt-instance:item key="volumeID" > type="str">5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc</ovirt-instance:item> > <ovirt-instance:item key="specParams" type="dict"/> > <ovirt-instance:item key="volumeChain" type="list"> > <ovirt-instance:item index="0" type="dict"> > <ovirt-instance:item key="domainID" > type="str">c578566d-bc61-420c-8f1e-8dfa0a18efd5</ovirt-instance:item> > <ovirt-instance:item key="volType" > type="str">path</ovirt-instance:item> > <ovirt-instance:item key="leaseOffset" > type="int">0</ovirt-instance:item> > <ovirt-instance:item key="path" > type="str">/rhev/data-center/mnt/192.168.1.20:_srv_virtstore_nfs_rel40x_data/c578566d-bc61-420c-8f1e-8dfa0a18efd5/images/66441539-f7ac-4946-8a25-75e422f939d4/5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc</ovirt-instance:item> > <ovirt-instance:item key="volumeID" > type="str">5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc</ovirt-instance:item> > <ovirt-instance:item key="leasePath" > type="str">/rhev/data-center/mnt/192.168.1.20:_srv_virtstore_nfs_rel40x_data/c578566d-bc61-420c-8f1e-8dfa0a18efd5/images/66441539-f7ac-4946-8a25-75e422f939d4/5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc.lease</ovirt-instance:item> > <ovirt-instance:item key="imageID" > type="str">66441539-f7ac-4946-8a25-75e422f939d4</ovirt-instance:item> > </ovirt-instance:item> > </ovirt-instance:item> > </ovirt-instance:item> > </ovirt-instance:item> > </ovirt-instance:value> > </ovirt-instance:instance> > </metadata> > <maxMemory slots='16' unit='KiB'>4294967296</maxMemory> > <memory unit='KiB'>4194304</memory> > <currentMemory unit='KiB'>4194304</currentMemory> > <vcpu placement='static' current='2'>16</vcpu> > <cputune> > <shares>1020</shares> > </cputune> > <resource> > <partition>/machine</partition> > </resource> > <sysinfo type='smbios'> > <system> > <entry name='manufacturer'>oVirt</entry> > <entry name='product'>oVirt Node</entry> > <entry name='version'>7-3.1611.el7.centos</entry> > <entry name='serial'>ccd79775-c888-4789-975a-fde1143dffc9</entry> > <entry name='uuid'>ccd945c8-8069-4f31-8471-bbb58e9dd6ea</entry> > </system> > </sysinfo> > <os> > <type arch='x86_64' machine='pc-i440fx-rhel7.2.0'>hvm</type> > <bios useserial='yes'/> > <smbios mode='sysinfo'/> > </os> > <features> > <acpi/> > </features> > <cpu mode='custom' match='exact'> > <model fallback='allow'>Haswell-noTSX</model> > <topology sockets='16' cores='1' threads='1'/> > <numa> > <cell id='0' cpus='0-1' memory='4194304' unit='KiB'/> > </numa> > </cpu> > <clock offset='variable' adjustment='0' basis='utc'> > <timer name='rtc' tickpolicy='catchup'/> > <timer name='pit' tickpolicy='delay'/> > <timer name='hpet' present='no'/> > </clock> > <on_poweroff>destroy</on_poweroff> > <on_reboot>restart</on_reboot> > <on_crash>destroy</on_crash> > <devices> > <emulator>/usr/libexec/qemu-kvm</emulator> > <controller type='virtio-serial' index='0' ports='16'> > <alias name='virtio-serial0'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x04' > function='0x0'/> > </controller> > <controller type='usb' index='0'> > <alias name='usb'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x01' > function='0x2'/> > </controller> > <controller type='pci' index='0' model='pci-root'> > <alias name='pci.0'/> > </controller> > <controller type='ide' index='0'> > <alias name='ide'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x01' > function='0x1'/> > </controller> > <interface type='bridge'> > <mac address='00:1a:4a:16:01:51'/> > <source bridge='ovirtmgmt'/> > <target dev='vnet0'/> > <model type='virtio'/> > <filterref filter='vdsm-no-mac-spoofing'/> > <link state='up'/> > <alias name='net0'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x03' > function='0x0'/> > </interface> > <serial type='unix'> > <source mode='bind' > path='/var/run/ovirt-vmconsole-console/ccd945c8-8069-4f31-8471-bbb58e9dd6ea.sock'/> > <target port='0'/> > <alias name='serial0'/> > </serial> > <console type='unix'> > <source mode='bind' > path='/var/run/ovirt-vmconsole-console/ccd945c8-8069-4f31-8471-bbb58e9dd6ea.sock'/> > <target type='serial' port='0'/> > <alias name='serial0'/> > </console> > <channel type='unix'> > <source mode='bind' > path='/var/lib/libvirt/qemu/channels/ccd945c8-8069-4f31-8471-bbb58e9dd6ea.com.redhat.rhevm.vdsm'/> > <target type='virtio' name='com.redhat.rhevm.vdsm' > state='disconnected'/> > <alias name='channel0'/> > <address type='virtio-serial' controller='0' bus='0' port='1'/> > </channel> > <channel type='unix'> > <source mode='bind' > path='/var/lib/libvirt/qemu/channels/ccd945c8-8069-4f31-8471-bbb58e9dd6ea.org.qemu.guest_agent.0'/> > <target type='virtio' name='org.qemu.guest_agent.0' > state='disconnected'/> > <alias name='channel1'/> > <address type='virtio-serial' controller='0' bus='0' port='2'/> > </channel> > <channel type='spicevmc'> > <target type='virtio' name='com.redhat.spice.0' state='disconnected'/> > <alias name='channel2'/> > <address type='virtio-serial' controller='0' bus='0' port='3'/> > </channel> > <input type='mouse' bus='ps2'> > <alias name='input0'/> > </input> > <input type='keyboard' bus='ps2'> > <alias name='input1'/> > </input> > <graphics type='vnc' port='5900' autoport='yes' > listen='192.168.1.53' keymap='en-us' passwdValidTo='1970-01-01T00:00:01'> > <listen type='network' address='192.168.1.53' > network='vdsm-ovirtmgmt'/> > </graphics> > <graphics type='spice' tlsPort='5901' autoport='yes' > listen='192.168.1.53' keymap='en-us' defaultMode='secure' > passwdValidTo='1970-01-01T00:00:01'> > <listen type='network' address='192.168.1.53' > network='vdsm-ovirtmgmt'/> > <channel name='main' mode='secure'/> > <channel name='display' mode='secure'/> > <channel name='inputs' mode='secure'/> > <channel name='cursor' mode='secure'/> > <channel name='playback' mode='secure'/> > <channel name='record' mode='secure'/> > <channel name='smartcard' mode='secure'/> > <channel name='usbredir' mode='secure'/> > </graphics> > <sound model='ich6'> > <alias name='sound0'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x06' > function='0x0'/> > </sound> > <video> > <model type='qxl' ram='65536' vram='8192' vgamem='16384' heads='1' > primary='yes'/> > <alias name='video0'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x02' > function='0x0'/> > </video> > <memballoon model='virtio'> > <alias name='balloon0'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x07' > function='0x0'/> > </memballoon> > </devices> > <seclabel type='dynamic' model='selinux' relabel='yes'> > <label>system_u:system_r:svirt_t:s0:c207,c629</label> > <imagelabel>system_u:object_r:svirt_image_t:s0:c207,c629</imagelabel> > </seclabel> > <seclabel type='dynamic' model='dac' relabel='yes'> > <label>+107:+107</label> > <imagelabel>+107:+107</imagelabel> > </seclabel> > </domain> > > > On 03/15/2017 01:28 PM, Francesco Romani wrote: >> Hi everyone, >> >> This is both a report of the current state of my Vdsm patches for Engine >> XML support, and a proposal to how move forward and solve >> the current open issues. >> >> TL;DR: >> 1. we can and IMO should reuse the current JSON schema to describe the >> structure (layout) and the types of the metadata section. >> 2. we don't need a priori validation of stuff in the metadata section. >> We will just raise in the creation flow if data is missing, or wrong, >> according to our schema. >> 2. we will add *few* items to the metadata section, only thing we can't >> express clearly-or at all in the libvirt XML. Redundancy and verbosiness >> will be thus kept at bay >> 3. I believe [3] is the best tool to do (de)serialize data to the >> metadata section. Existing tools fits poorly in our very specific use case >> >> Examples below >> >> +++ >> >> Long(er) discussion: >> >> >> I have working code[1][2] to encode any custom, picklable, python >> object in the metadata section. >> >> We should decide which module will do the actual python<=>XML >> transformation. >> Please note that this actually also influences how the data in the >> medata section look like, so the two things are a bit coupled. >> >> I'm eager to reinvent another wheel, but after >> initial evaluation I honestly think that my pyxmlpickle[3] is the best >> tool for the job over the current alternatives: plistlib[4] and >> xmltodict[5]. >> >> I added the initial rationale here: >> https://gerrit.ovirt.org/#/c/73790/4//COMMIT_MSG >> >> I have completed the initial draft of patches to make it possible to >> initialize devices from their XML representation [6]. This is the bare >> minimum we need to support the Engine XML, and we *need* this anyway to >> unlock the cleanup we planned and I outlined in my google doc. >> >> So we are progressing, but I'd like to speed up things. Those [6] >> patches are not yet complete, many flows are not covered or tested; but >> they are good enough to demonstrate that there *are* pieces of >> information wen need to properly initialize the devices, but we can't >> easily extract from the XML. >> >> First examples that come to my mind are the storage.Drive UUIDs; there >> could also be some ambiguity I'm investigating right now for >> displayIp/displayNetwork in Graphics devices. In [6] there are various >> TODO to mark more of those cases. Most likely, few more cases will pop >> out as I cover all the flows we support. >> >> Long story short: it is hard to correctly rebuild the device conf from >> the XML. This is why in [6] I added the 'meta' argument to from_xml_tree >> classmethod in [7]. >> >> 'meta' is supposed to be the device metadata: extra data related to a >> device which doesn't (yet) fit in the libvirt XML representation. >> For example, we can store 'displayIp' and 'displayNetwork' here and be >> done with that: using both per-device metadata and the XML >> representation of one graphic device, we will have everything we need to >> properly build one graphics.Graphics device. >> This example may (hopefully) be bogus, but I'm keeping it because it is >> one case easy to follow. >> >> The device metadata is going to be stored in the vm metadata for the >> short/mid term future. Even if the per-device metadata idea/RFE is >> accepted (no answer yet, but we are working on it), we will not have in >> 7.4, and unlikely in 7.5. >> >> As it stands today, I believe there are two open questions: >> >> 1. do we need a schema for the metadata section? >> 2. how do we bind the metadata to the devices? How do we know which >> metadata belongs to which metadata, if we don't have aliases nor >> addresses to match? (e.g. very first time the VM is created!) >> >> My current stance is the following >> 1. In general, one schema gives us two benefits: 1.a. we document how >> the layout of the data should be, including types; 1.b. we can validate >> the data we receive. >> So yes, we need a schema, but we don't need a *new* schema. I think we >> are in good enough shape with the current Vdsm schema: we can just >> translate the python object layout to a XML layout. >> >> One example is probably more explicative. Some actual data may look >> like, using my pyxmlpickle module: >> >> <domain type='kvm' id='5'> >> <name>a0</name> >> <uuid>ccd945c8-8069-4f31-8471-bbb58e9dd6ea</uuid> >> <metadata xmlns:ovirt-tune="http://ovirt.org/vm/tune/1.0" >> xmlns:ovirt-vm="http://ovirt.org/vm/1.0" >> xmlns:ovirt-instance="http://ovirt.org/vm/instance/1.0"> >> <ovirt-tune:qos/> >> <ovirt-vm:vm/> >> <ovirt-instance:instance> >> <ovirt-instance:value type="dict"> >> <ovirt-instance:item key="devices" type="list"> >> <ovirt-instance:item index="0" type="dict"> >> <ovirt-instance:item key="device" >> type="str">vnc</ovirt-instance:item> >> <ovirt-instance:item key="specParams" type="dict"> >> <ovirt-instance:item key="displayNetwork" >> type="str">ovirtmgmt</ovirt-instance:item> >> <ovirt-instance:item key="displayIp" >> type="str">192.168.1.53</ovirt-instance:item> >> </ovirt-instance:item> >> <ovirt-instance:item key="type" >> type="str">graphics</ovirt-instance:item> >> </ovirt-instance:item> >> <ovirt-instance:item index="1" type="dict"> >> <ovirt-instance:item key="device" >> type="str">spice</ovirt-instance:item> >> <ovirt-instance:item key="specParams" type="dict"> >> <ovirt-instance:item key="displayNetwork" >> type="str">ovirtmgmt</ovirt-instance:item> >> <ovirt-instance:item key="displayIp" >> type="str">192.168.1.53</ovirt-instance:item> >> </ovirt-instance:item> >> <ovirt-instance:item key="type" >> type="str">graphics</ovirt-instance:item> >> </ovirt-instance:item> >> <ovirt-instance:item index="2" type="dict"> >> <ovirt-instance:item key="poolID" >> type="str">5890a292-0390-01d2-01ed-00000000029a</ovirt-instance:item> >> <ovirt-instance:item key="imageID" >> type="str">66441539-f7ac-4946-8a25-75e422f939d4</ovirt-instance:item> >> <ovirt-instance:item key="domainID" >> type="str">c578566d-bc61-420c-8f1e-8dfa0a18efd5</ovirt-instance:item> >> <ovirt-instance:item key="device" >> type="str">disk</ovirt-instance:item> >> <ovirt-instance:item key="path" >> type="str">/rhev/data-center/5890a292-0390-01d2-01ed-00000000029a/c578566d-bc61-420c-8f1e-8dfa0a18efd5/images/66441539-f7ac-4946-8a25-75e422f939d4/5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc</ovirt-instance:item> >> <ovirt-instance:item key="volumeID" >> type="str">5c4eeed4-f2a7-490a-ab57-a0d6f3a711cc</ovirt-instance:item> >> </ovirt-instance:item> >> </ovirt-instance:item> >> </ovirt-instance:value> >> </ovirt-instance:instance> >> </metadata> >> <!-- omitted for brevity --> >> </domain> >> >> >> Please note that yes, this is still verbose, but we don't want to add >> much data here, for most of information the most reliable source will >> be the domain XML. We will add here only the extra info we can't really >> fetch from that. >> >> 2. I don't think we need explicit validation: we could just raise along >> the way in the creation flow if we don't find some extra metadata we >> need. This will also solve the issue that if we reuse the current schema >> and we omit most of data, we will lack quite a lot of elements >> marked mandatory. >> >> Once we reached agreement, I will update my >> https://docs.google.com/document/d/1eD8KSLwwyo2Sk64MytbmE0wBxxMlpIyEI1GRc... >> accordingly. >> >> Final note: while device take the lion's share, we will likely need help >> from the metadata section also to store VM extra info, but all the above >> discussion also applies here. >> >> +++ >> >> [1] >> https://gerrit.ovirt.org/#/q/status:open+project:vdsm+branch:master+topic... >> - uses xmltodict >> [2] >> https://gerrit.ovirt.org/#/q/status:open+project:vdsm+branch:master+topic... >> ported the 'virt-metadata3' topic to pyxmlpickle >> [3] https://github.com/fromanirh/pyxmlpickle >> [4] https://docs.python.org/2/library/plistlib.html >> [5] https://github.com/martinblech/xmltodict >> [6] >> https://gerrit.ovirt.org/#/q/status:open+project:vdsm+branch:master+topic... >> [7] https://gerrit.ovirt.org/#/c/72880/15/lib/vdsm/virt/vmdevices/core.py >> > -- > Francesco Romani > Red Hat Engineering Virtualization R & D > IRC: fromani > > _______________________________________________ > Devel mailing list > Devel(a)ovirt.org > http://lists.ovirt.org/mailman/listinfo/devel > >