[Engine-devel] Updates in VdsUpdateRuntimeInfo

[Eli Mesika]

----- Original Message -----
> From: "Barak Azulay" <bazulay at redhat.com>
> To: "Itamar Heim" <iheim at redhat.com>
> Cc: "engine-devel" <engine-devel at ovirt.org>
> Sent: Wednesday, June 12, 2013 10:45:25 AM
> Subject: Re: [Engine-devel] Updates in VdsUpdateRuntimeInfo
> 
> 
> 
> ----- Original Message -----
> > From: "Itamar Heim" <iheim at redhat.com>
> > To: "Barak Azulay" <bazulay at redhat.com>
> > Cc: "engine-devel" <engine-devel at ovirt.org>
> > Sent: Wednesday, June 12, 2013 10:09:09 AM
> > Subject: Re: [Engine-devel] Updates in VdsUpdateRuntimeInfo
> > 
> > On 06/12/2013 09:41 AM, Barak Azulay wrote:
> > >
> > >
> > > ----- Original Message -----
> > >> From: "Itamar Heim" <iheim at redhat.com>
> > >> To: "Liran Zelkha" <lzelkha at redhat.com>
> > >> Cc: "engine-devel" <engine-devel at ovirt.org>
> > >> Sent: Tuesday, June 11, 2013 4:00:21 PM
> > >> Subject: Re: [Engine-devel] Updates in VdsUpdateRuntimeInfo
> > >>
> > >> On 06/11/2013 03:26 PM, Liran Zelkha wrote:
> > >>> Hi all,
> > >>>
> > >>> I'm checking performance for VdsUpdateRunTimeInfo.
> > >>> Naturally, much of the performance surrounds database activity
> > >>> (getVmsRunningOnVds queries, updateDeviceRuntimeInfo, updateVmDynamic)
> > >>>
> > >>> Few questions:
> > >>> 1. I have implemented batch updates for procedure
> > >>> UpdateVmDeviceRuntimeInfo
> > >>> for improved performance.
> > >>> 2. Seems like the only parameters UpdateVmDeviceRuntimeInfo is getting
> > >>> are
> > >>> vm_id,vm_device_id,address and alias. Are those rapidly changing, or
> > >>> will
> > >>> it be beneficial to implement caching on those updates (to ensure
> > >>> not-required updates do not travel to the database).
> > >>
> > >> slowly changing, but how will you cover all flows changing these devices
> > >> to invalidate the cache (iiuc, this table is modified by engine when
> > >> adding devices to a VM as well?)
> > >
> > >
> > > I don't think that in the device run time info we need to invalidate once
> > > we add a device.
> > > This is a specific case where we actually get the information from the
> > > VDSM
> > > (addresses are received from libvirt)
> > > The commands IIRC are first send to VDSM and than update the runtime info
> > > only on changed info (we can also hash it),
> > > It may put the placeholder in the DB first but it still relies on the
> > > data
> > > received from VDSM.
> > 
> > if this table is only updated from vdsm to save it, i agree.
> > but isn't the engine also manipulating it?
> > wasn't there a request to be able to maybe edit the addresses some day?
> 
> Even if there was such a request, we still update when we receive the info
> from libvirt.
> 
> Anyway there are obviously a few improvements to be done before caching.
> - update only when info received from VDSM change (need to verify it is the
> practice here)

This should be the behavior right now
There is a hash column in vm_dynamic , this hash is passed by VDSM
We are updating only VMs that change their hash value 

> - do batch update for the new updated data received.
> - do the hashing (of vm device runtime info) on VDSM for the data , and
> update only when hash changes
> - caching ...
> 
> Barak
>  
> 
> 
> > 
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> > 
> > 
> > 
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