On 17.10.2016 20:46, Nikolay Shirokovskiy wrote:
> Hi, all.
> We would like to use virDomainQemuMonitorCommand to query qemu independently
> libvirt state. Currenly it is not possible. This API call takes job condition
> just like any other call and thus is unavailable on any lengthy(or stucked)
> synchronous job.
> I've already posted this question in list, just failed to find the reference.
> Somebody suggested to use proxy (and even an implementation) in between qemu
> and libvirt that can inject commands to qemu and filter replies. It is not
> really convinient. This way test setups will be different from production and
> we can not investigate problems in production environment.
> I'd like to drop acquiring job condition in the call as this function does not
> deal with libvirt state (except for the taint but is is ok, we will not mess
> things up here). But this is not enough, we need to make qemu monitor deal
> many qemu commands simultaneously. Looks like it is quite a big change for
> test/debug case. But I guess eventually normal user cases can get benefits too
> from this monitor changes. For example all query API calls that query qemu
> directly can be changed to not to wait for some synchronous job
> finishing.(qemuDomainGetBlockJobInfo for example).
IIRC the last time I looked into this the problem was not on libvirt
side. QEMU's monitor was unable to process multiple commands at once.
But maybe that's no longer the case, I don't know.
However, what I think we should do is to turn our jobs into sort of RW
locks. That is - we could allow multiple QUERY jobs to happen
simultaneously and leave MODIFY jobs to be exclusive. I think dropping
BeginJob() from an API is a no go as it will definitely bite us in the
Unfortunately, I have no idea what my suggestion would look like in
terms of the code. How difficult it would be to implement it (and
whether monitor code is prepared for that).
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