5:05 p.m.
Hi,
This proposal is a follow up on a previous discussion about
optimizing the communication between VDSM and the ovirt-engine.
Currently the engine polls VDSM every 3 seconds with the `list`
verb to retrieve the status of all VMs. Every 5th time (every 15
seconds) it alternates to 'getAllVmStats' which gives more
information about the VMs.
Quite a big portion of the data, mainly the reply of getAllVmStats,
is only of interest if it actually changes so that the engine/back-end
can act on changes and update rows accordingly.
Now the problem is that there is quite a lot of data transferred
which is not really necessary and there is a 15 seconds delay on
communicating changes to certain VMs before the engine actually
can react on them and before these changes can be communicated
to the user.
As part of an improvement on this matter I'd like to propose a new API
verb for VDSM:
Host.queryVms(vmIds=[], fields=[], exclude=[], changedSince='')
This new verb is intended to eventually replace 2 currently
used verbs `list` and `getAllVmStats`. `queryVms` is supposed to
allow to request any data fields of a VM which can be requested through
the public API:
- Statistics
- Configuration
- Status information
- Guest OS Information
I have executed some tests and in those tested scenarios the new Verb
can result in an improvement of 75%-90% of data transferred and average
response body size depending on the scenario and usage.
The test results can be found here:
http://www.ovirt.org/Feature/VDSM_VM_Query_API/Measurements#Results
(An explanation of the tested methods is on the top of the page and a
description of the scenario in each section)
The benefit of introducing this verb would be a lowered volume of data
transferred over the management network which avoids congestion
on huge setups and can introduce an increased responsiveness for
communicating changes in state to the user. For example live migration
status. However even SLA related changes could be communicated faster
for things like QoS.
Preliminary Feature Proposal Wiki:
http://www.ovirt.org/Feature/VDSM_VM_Query_API
--
Regards,
Vinzenz Feenstra | Senior Software Engineer
RedHat Engineering Virtualization R & D
Phone: +420 532 294 625
IRC: vfeenstr or evilissimo
Better technology. Faster innovation. Powered by community collaboration.
See how it works at redhat.com
5:20 p.m.
Thanks for this effort, I hope I understand
this correctly, that your new API still works
the same way?
So engine pulls constantly from vdsm?
If I understand the architecture correctly
this should not be necessary, so vdsm could
push updates to engine, when there are updates
and engine could just query vdsm when a specified
timeout without push notification occurs.
I think this would scale better for higher numbers
of vdsm, in fact for very high vdsm numbers
connected to one engine something like a message queue
implementation would scale even better (zero mq).
--
Mit freundlichen Grüßen / Regards
Sven Kieske
Systemadministrator
Mittwald CM Service GmbH & Co. KG
Königsberger Straße 6
32339 Espelkamp
T: +49-5772-293-100
F: +49-5772-293-333
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
5:37 p.m.
On Jul 14, 2014, at 16:20 , Sven Kieske <S.Kieske(a)mittwald.de> wrote:
Thanks for this effort, I hope I understand
this correctly, that your new API still works
the same way?
So engine pulls constantly from vdsm?
yes
If I understand the architecture correctly
this should not be necessary, so vdsm could
push updates to engine, when there are updates
and engine could just query vdsm when a specified
timeout without push notification occurs.
yes, push notifications are still in plan, we only recently added the infrastructural
foundations with json-rpc, it will take some time before we can adjust
Thanks,
michal
I think this would scale better for higher numbers
of vdsm, in fact for very high vdsm numbers
connected to one engine something like a message queue
implementation would scale even better (zero mq).
--
Mit freundlichen Grüßen / Regards
Sven Kieske
Systemadministrator
Mittwald CM Service GmbH & Co. KG
Königsberger Straße 6
32339 Espelkamp
T: +49-5772-293-100
F: +49-5772-293-333
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
12:29 p.m.
On 07/14/2014 04:05 PM, Vinzenz Feenstra wrote:
Hi,
Since this mail did not receive enough attention I am
bumping it again.
For this proposal exists currently a draft patch
http://gerrit.ovirt.org/#/c/28819/
The patch is not final since the query function should not require to
update all the data
on every call. (This should be done directly by data modifying code.
However that would be implemented by follow up patches)
The trackable.py implementation also can be easily extended in future
for enabling push notifications to the engine once
we switched to the new communication. This could be done by subscribing
to certain keys in the TrackableMapping instance.
(Not implemented yet)
Anyway I am asking once more for comments on the proposal.
This proposal is a follow up on a previous discussion about
optimizing the communication between VDSM and the ovirt-engine.
Currently the engine polls VDSM every 3 seconds with the `list`
verb to retrieve the status of all VMs. Every 5th time (every 15
seconds) it alternates to 'getAllVmStats' which gives more
information about the VMs.
Quite a big portion of the data, mainly the reply of getAllVmStats,
is only of interest if it actually changes so that the engine/back-end
can act on changes and update rows accordingly.
Now the problem is that there is quite a lot of data transferred
which is not really necessary and there is a 15 seconds delay on
communicating changes to certain VMs before the engine actually
can react on them and before these changes can be communicated
to the user.
As part of an improvement on this matter I'd like to propose a new API
verb for VDSM:
Host.queryVms(vmIds=[], fields=[], exclude=[], changedSince='')
This new verb is intended to eventually replace 2 currently
used verbs `list` and `getAllVmStats`. `queryVms` is supposed to
allow to request any data fields of a VM which can be requested through
the public API:
- Statistics
- Configuration
- Status information
- Guest OS Information
I have executed some tests and in those tested scenarios the new Verb
can result in an improvement of 75%-90% of data transferred and average
response body size depending on the scenario and usage.
The test results can be found here:
http://www.ovirt.org/Feature/VDSM_VM_Query_API/Measurements#Results
(An explanation of the tested methods is on the top of the page and a
description of the scenario in each section)
The benefit of introducing this verb would be a lowered volume of data
transferred over the management network which avoids congestion
on huge setups and can introduce an increased responsiveness for
communicating changes in state to the user. For example live migration
status. However even SLA related changes could be communicated faster
for things like QoS.
Preliminary Feature Proposal Wiki:
http://www.ovirt.org/Feature/VDSM_VM_Query_API
--
Regards,
Vinzenz Feenstra | Senior Software Engineer
RedHat Engineering Virtualization R & D
Phone: +420 532 294 625
IRC: vfeenstr or evilissimo
Better technology. Faster innovation. Powered by community collaboration.
See how it works at redhat.com
3 p.m.
----- Original Message -----
From: "Vinzenz Feenstra" <vfeenstr(a)redhat.com>
To: devel(a)ovirt.org
Sent: Tuesday, July 22, 2014 11:29:40 AM
Subject: Re: [ovirt-devel] "Host.queryVms": A proposal for new a VDSM API verb
On 07/14/2014 04:05 PM, Vinzenz Feenstra wrote:
> Hi,
Since this mail did not receive enough attention I am bumping it again.
For this proposal exists currently a draft patch
http://gerrit.ovirt.org/#/c/28819/
The patch is not final since the query function should not require to
update all the data
on every call. (This should be done directly by data modifying code.
However that would be implemented by follow up patches)
The trackable.py implementation also can be easily extended in future
for enabling push notifications to the engine once
we switched to the new communication. This could be done by subscribing
to certain keys in the TrackableMapping instance.
(Not implemented yet)
Nice! Both nice to have now and on top of json/push notifications tomorrow.
I just had a quick look to the changes to vm.py and to the interface
and looks nice as well.
[...]
> I have executed some tests and in those tested scenarios the new
Verb
> can result in an improvement of 75%-90% of data transferred and average
> response body size depending on the scenario and usage.
>
> The test results can be found here:
> http://www.ovirt.org/Feature/VDSM_VM_Query_API/Measurements#Results
> (An explanation of the tested methods is on the top of the page and a
> description of the scenario in each section)
Nice graphs :)
Silly comment: having units in 'bytes' on the X-axis makes the numbers somehow
hard to parse (to me). I suggest you to convert them to KiB for better readability.
The savings look really nice.
Bests,
--
Francesco Romani
RedHat Engineering Virtualization R & D
Phone: 8261328
IRC: fromani
3:04 p.m.
On 07/22/2014 02:00 PM, Francesco Romani wrote:
----- Original Message -----
> From: "Vinzenz Feenstra" <vfeenstr(a)redhat.com>
> To: devel(a)ovirt.org
> Sent: Tuesday, July 22, 2014 11:29:40 AM
> Subject: Re: [ovirt-devel] "Host.queryVms": A proposal for new a VDSM API
verb
>
> On 07/14/2014 04:05 PM, Vinzenz Feenstra wrote:
>> Hi,
> Since this mail did not receive enough attention I am bumping it again.
>
> For this proposal exists currently a draft patch
> http://gerrit.ovirt.org/#/c/28819/
> The patch is not final since the query function should not require to
> update all the data
> on every call. (This should be done directly by data modifying code.
> However that would be implemented by follow up patches)
>
> The trackable.py implementation also can be easily extended in future
> for enabling push notifications to the engine once
> we switched to the new communication. This could be done by subscribing
> to certain keys in the TrackableMapping instance.
> (Not implemented yet)
Nice! Both nice to have now and on top of json/push notifications tomorrow.
I just had a quick look to the changes to vm.py and to the interface
and looks nice as well.
[...]
>> I have executed some tests and in those tested scenarios the new Verb
>> can result in an improvement of 75%-90% of data transferred and average
>> response body size depending on the scenario and usage.
>>
>> The test results can be found here:
>> http://www.ovirt.org/Feature/VDSM_VM_Query_API/Measurements#Results
>> (An explanation of the tested methods is on the top of the page and a
>> description of the scenario in each section)
Nice graphs :)
Silly comment: having units in 'bytes' on the X-axis makes the numbers somehow
hard to parse (to me). I suggest you to convert them to KiB for better readability.
The savings look really nice.
The table below shows it in MiB in a separate column
Bests,
--
Regards,
Vinzenz Feenstra | Senior Software Engineer
RedHat Engineering Virtualization R & D
Phone: +420 532 294 625
IRC: vfeenstr or evilissimo
Better technology. Faster innovation. Powered by community collaboration.
See how it works at redhat.com
7:15 p.m.
In 3.6 we are intending to have events in the json-rpc interface.
That means that a lot of the problems this is trying to fix will
no longer be an issue.
Changes about VM status will be sent as soon as they are available
instead of when the engine is polling.
This means that the messages will be smaller. We will also be
introducing compression which would make things even faster.
I also expressed my problems with VDSM keeping state.
When we move to an event driven system there would be no reason
to cache data anymore as internal polling would generate messages
and external polling would be used *only* to get up to date
information.
With call overhead being minimal getAllVmStats would just become
a list of getVmStats() for every VM of interest making the
filtering redundant.
Also, without internal caching it would also make the interface
of specifying the fields to include or exclude a bit problematic.
Having a bitflag (or a list of flags) to specify what type of
information is needed as it is easier to figure out what actual
calls need to be made. It is also easier for the user to know
that they are adding overhead to the response this way.
----- Original Message -----
From: "Vinzenz Feenstra" <vfeenstr(a)redhat.com>
To: devel(a)ovirt.org
Sent: Monday, July 14, 2014 5:05:17 PM
Subject: [ovirt-devel] "Host.queryVms": A proposal for new a VDSM API verb
Hi,
This proposal is a follow up on a previous discussion about
optimizing the communication between VDSM and the ovirt-engine.
Currently the engine polls VDSM every 3 seconds with the `list`
verb to retrieve the status of all VMs. Every 5th time (every 15
seconds) it alternates to 'getAllVmStats' which gives more
information about the VMs.
Quite a big portion of the data, mainly the reply of getAllVmStats,
is only of interest if it actually changes so that the engine/back-end
can act on changes and update rows accordingly.
Now the problem is that there is quite a lot of data transferred
which is not really necessary and there is a 15 seconds delay on
communicating changes to certain VMs before the engine actually
can react on them and before these changes can be communicated
to the user.
As part of an improvement on this matter I'd like to propose a new API
verb for VDSM:
Host.queryVms(vmIds=[], fields=[], exclude=[], changedSince='')
This new verb is intended to eventually replace 2 currently
used verbs `list` and `getAllVmStats`. `queryVms` is supposed to
allow to request any data fields of a VM which can be requested through
the public API:
- Statistics
- Configuration
- Status information
- Guest OS Information
I have executed some tests and in those tested scenarios the new Verb
can result in an improvement of 75%-90% of data transferred and average
response body size depending on the scenario and usage.
The test results can be found here:
http://www.ovirt.org/Feature/VDSM_VM_Query_API/Measurements#Results
(An explanation of the tested methods is on the top of the page and a
description of the scenario in each section)
The benefit of introducing this verb would be a lowered volume of data
transferred over the management network which avoids congestion
on huge setups and can introduce an increased responsiveness for
communicating changes in state to the user. For example live migration
status. However even SLA related changes could be communicated faster
for things like QoS.
Preliminary Feature Proposal Wiki:
http://www.ovirt.org/Feature/VDSM_VM_Query_API
--
Regards,
Vinzenz Feenstra | Senior Software Engineer
RedHat Engineering Virtualization R & D
Phone: +420 532 294 625
IRC: vfeenstr or evilissimo
Better technology. Faster innovation. Powered by community collaboration.
See how it works at redhat.com
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6 comments
5 participants
participants (5)
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Francesco Romani -
Michal Skrivanek -
Saggi Mizrahi -
Sven Kieske -
Vinzenz Feenstra