Please see my inline comments. There are quite a few.
On 05/15/2012 01:38 PM, Itamar Heim wrote:
On 04/29/2012 01:41 PM, Gary Kotton wrote:
> As part of a POC we have integrated Quantum
) into oVirt (http://www.ovirt.org/
> This has been tested with the OVS and Linux Bridge plugins.
> The details of the integration can be found at -
> Any comments and suggestions would be greatly appreciated.
Thanks Gary - some questions:
1. you are using the term 'user' for both an end-user and an admin. I
think admin is more appropriate in most places.
2. host management --> interface
2.1 you are suggesting to remove the vlan field with a fabric field?
Yes, this is
what I am suggesting. VLAN tagging is one method of network
isolation. There are more, for example GRE tunneling.
are we sure this is something which shouldn't be presented in the
view and only via extended properties?
2.2 is the fabric really a host interface level property, or a cluster
wide property (would same logical network be implemented on different
hosts in the cluster via both vdsm and quantum)?
would live migration work in same cluster if one host has qunatum
fabric and another vdsm fabric for same logical network?
These are all up for
discussion. I just wanted to provide something that
we can start to work with. It would be nice if there was some input from
product management on this issue (not exactly sure how this works in an
open source community :))
2.3 you are describing the subtab of an interface, and mention a
qunatum pull down menu. is this in the subtab? in a dialog?
UI mockups are needed here.
I think that prior to getting mockups, we should ensure
that we have the
2.4 also, is this pulldown correct at host level or cluster level
(would live migration work between hosts implementing different
plugins for same logical network in same cluster?)
on to backend:
3.1 "The Quantum Service is a process that runs the Quantum API web
server (port 9696)"
how is authentication between engine and quantum service is done (we
have a client certificate for engine which qunatum can verify i guess)
opinion this should be running locally on the same host as the
3.2 is there a config of the quantum service uri? should it be a
single instance or a per DC property?
(it sounds like a per DC property, can be a future thing)
I am sorry but I do not
understand the question.
3.3 network creation
semantics: we create a network at DC level. we attach it at cluster
level. the UI allows you to "create at DC and attach to cluster" at
3.3.1 what if i create a network with same VLAN in two DC's? what if
we attach same logical network to multiple clusters - each will create
the logical network in qunatum again?
If I understand you correctly then I think
that one Quantum network can
be created. This should work. In my opinion this should be managed by
the oVirt engine so the actual creation is not an issue. Ensuring that
each cluster has the correct network management configurations is what
3.3.2 what if the qunatum service is down when engine performs this
action or quantum returns an error?
The engine should be able to deal with this -
similar to the way in
which it deals with a network creation when VDSM is down.
3.3.3 each creation of a DC creates a rhevm network - I assume these
are not created, since "no host in a cluster in the DC yet"?
functionally can remain the same.
3.3.4 what happens on moving of a host to another cluster, or moving
of a cluster to another DC (possible if it's DC was removed iirc).
agents take care of this. On each host there will be a
Quantum agent that treats the network management.
3.3.5 shouldn't this be limited to vm networks, or all networks
I think all Quantum networks are relevant
3.3.6 what if the host with the qunatum fabric is in maint mode?
I do not understand. When a host is in maintenace mode do VM's receive
traffic? The Quantum port for the VM's can be set as DOWN
3.3.7 could a host with qunatum fabric have a VDSM fabric on another
interface (for vm neworks? for non-vm networks)?
Yes. This is something that I
would like. I also would like the Quantum
API to be updated so that we can indicate the phycal network interface
that the Quantum network will be running on.
3.5 network deletion (detach network from a cluster)
3.5.1 what happens if qunatum is down or returned an error?
The engine should be
able to deal with this - similarly to what it does
3.6 vm creation
3.6.1 what about moving a VM from/to a cluster with a quantum fabric?
I do not see
a problem here. The agenets running on VDSM will detect and
3.6.2 what about import of a VM into a cluster with a qunatum fabric?
Same as above
3.6.3 you have vm creation/removal - missing vnic addition/removal
3.6.4 worth mentioning qunatum doesn't care about the vnic model?
about the mac address?
The Quantum driver on VDSM does take into account the MAC
is used in some plugins - for example the openvswicth plugin.
3.7 vm start
3.7.1 why is the plugin parameter required at vm start?
This is to indicate to
VDSM the operations to take place - for example
updating the openvswitch integration bridge
can multiple plugins be supported in parallel at vdsm/host level or
the quantum service?
Yes/ Multiple agents can run on VDSM. In the engine a little
required to run multiple plugins.
3.7.2 aren't network_uuid and port uuid redundant to attachment
(I assume qunatum service knows from attachment the port and network)
- i have no objection to passing them to vdsm, just trying to
understand reasoning for this.
I am missing what happens at vdsm level in this point (even after
reading the matching vdsm part)
The network ID and the port ID are returned by the
Quantum service. The
attachment ID is passed to the Quantum server. If this is unique then it
can be a key to the above (I am currently working on the scale issue
with Quantum and there are 2 options, the first is that it is unique,
the second is that all three are passed to the agent). It is a few extra
bytes passed. I think that it is better to be safe and have all of the
information on VDSM for future use.
3.8 vm suspend/resume (it's fine to say it behaves like X, but still
need to be covered to not cause bugs/regressions)
The Quantum port status can be
3.9 vm stop
Same as above
3.9.1 need to make sure vm stop when engine is down is handled
3.9.2 what happens if qunatum service is down? unlike start vm or
network creation the operation in this case cannot be
stopped/rolledback, only rolled forward.
We have to ensure that it is up.
3.10 hot plug nic?
Each new NIC has an attachment ID - the agent know that a new
added and treats accordingly.
3.11 vm migration
3.11.1 ok, so this is the first time i understand hosts can be mixed
in same cluster. worth specifying this in the beginning (still not
clear if mixed plugins can exist)
If the networks are configured with the same
characteristics then this
should be OK. As mentioned above we are working on a blueprint to deal
with connecting to existing networks - i.e. enable the user/admin to
configure the VLAN tags
3.11.2 afair, we don't deal with engine talking to both hosts
live migration. only to host A, who is then communicating with host B.
so why not always have the VM configuration at vm start (and hot plug
nic) have the quantum details so live migration can occur at will
without additional information?
I do not understand can you please explain. VDSM
creates the tap device
and builds the libvirt files. The agents detect the tap device and
attach to the network. I do not understand why it is a problem for the
live migration. This is also driven by the libvirt XML's being created.
Is this correct?
3.11.3 "In order to implement the above a REST client needs to
implemented in the oVirt engine. "
did not understand this statement - please elaborate.
All interface with the
Quantum server is done via REST. In order for
oVirt to be able to communicate, it will need to send REST messages to
the server and be able to parse the replies - this is what I meant by
the REST client.
4. host management
we do not deploy packages from engine to hosts, we can install them
from a repo configured to the host. but this is done today only as
part of initial bootstrap/installation of host.
also, it is not relevant for ovirt node which is 'firmware' like.
any reason to not require the 'plugin installation packages' at vdsm
rpm level for plugins we think are good enough to use (until then,
responsibility to deploy them is of admin)
Correct. I agree with you.
(what are plugin level packages at host level - aren't these the
Each plugin has the relevant packages that should be installed.
4.2 plugin configuration
per DC? per cluster? per host? per plugin? please provide more details
here on configuration details expected and flow of when they are
configured and when they are expected to change?
I think that plugin per cluster is
a good start. This could limit live
I think this will merit a per 'ovirt supported' qunatum
plugin to see
it works in a way we can use.
again, this requires more details. if needed per plugin.
what is expected? how authentication/encryption happens? what iptables
rules need to change in engine/host if at all, etc.
I'm fine with this being 'direct access to db from hosts' for POC
level of patches, but not for something we actually merge/provide
support for later.
I am currently working on a blueprint to ensure better scaling
quantum agents. This will be done by making use of the nova RPC library.
This supports Qpid, rabbit mq, kombu etc. These have an option of being
secure. Please clarify if this suffices?
5.1 s/The agent packe/The agent package/ ?
5.2 "The agent package can and may be received from the oVirt Engine
or can be downloaded via RPM's"
see 4.1 above - we don't deploy rpm's/code on the fly today.
When I was
sitting with the guys from oVirt this is what I was told. I
guess that I misunderstood.
5.3 "n addition to the treatment below VDSM should also maintain a
health check to the Quantum agent"
what if the restart didn't help? how should ovirt treat the host wrt
networking? to running VMs? to ability to live migrate VMs from the
host if needed?
If the agent is down then the oVirt engine should be notified to at
least events for the user.
5.4 "Logical Network Management"
please see 3.11 above - we would want live migration to not require
additional information, so details should be available even if not
immediately acted upon.
5.5 "The tap device created uses an "ethernet" network device. This
means that the creation of the libvirt XML file is a bit different."
5.5.1 does this impact stable device addresses somehow?
that I am aware of
5.5.2 how is live migration possible if the libvirt xml to a non
quantum host is different (or is this the binding part only)?
If the libvirt is
"pacthed" when the migration takes place then this
should not be a problem.
5.6 I assume libvirtvm.py is part of vdsm.
is quantum.py part of quantum code base or vdsm codebase (it sounds
like it should be part of quantum code base)?
so how exactly the rpm for this would look like? deploy it to
/xxx/qunatum and have it add a symbolic link to it from vdsm paths?
In my opinion
this should be part of VDSM. It would be ideal if each
plugin can bind load a driver - in Nova each driver is part of the nova
code. If the API is well defined then all vendors can provide their
drivers. This is open for discussion and we should try and understand
what the best way of doing this is. I like the NOVA model.
5.7 "When a communication channel is established between VDSM and the
oVirt engine. The VDSM host should notify the oVirt Engine of the
Quantum fabric that is supported."
how does vdsm goes about detecting an agent is installed exactly?
The user needs to
install a package for the agent - this creates the
relevant configuartion files. These files can be used to detect the
running agent or via "ps"
(especially since deployment wise, most likely is all agents would be
deployed via rpm requirements?)
is any agent a service at host level rather than code only?
is there a scenario where a vdsm level plugin isn't required?
6. open issues
6.1 worth mentioning if any are in the works
No shortage :). But we have a good
start. There are some blueprints in
the works which solve a large amount of problems
6.2 specifying the vlan from ovirt engine is not a gap?
is. This is currently being addressed. This is not a reason to
stop us moving ahead.
6.3 ok, so this is the first time "no multiple plugins" is
("Non-uniform technology"). but it sounds like the approach in the
wiki assume it is/will be possible to have multiple technologies
(agents/plugins) going forward?
My take is that this can be hidden by oVirt engine.
It is just an
implemnattion detail - this should not affect the user experience -
which at the end of the day is what counts
6.4 need to discuss which of the open issues should block going
forward with merging of code, and expected timeframe for resolution of
some of them
Correct. In my opinion there are no major blocking issues at the
7. other questions/items (some mentioned above as well)
7.1 please add ui mockups, db scheme changes and REST api changes
7.2 i'm missing the deployment flow:
- user install engine. is quantum a separate install or bundled going
- any configuration items by user at this point? what are they?
- what rpms are deployed at host level? what configuration do they need
- communication channels and their security are a must to understand
7.3 upgrade path / compatibility levels this is relevant to?
7.4 monitoring flow - how is monitoring/state of a host is affected by
quantum service being down, communication problem from host to (where