[libvirt] [PATCH] qemu_agent: report VIR_ERR_AGENT_UNSYNCED if guest_sync failed.

[Chen Hanxiao]

At 2017-11-30 14:11:36, "Nikolay Shirokovskiy" <nshirokovskiy at virtuozzo.com> wrote:
>
>
>On 30.11.2017 06:08, Chen Hanxiao wrote:
>> From: Chen Hanxiao <chenhanxiao at gmail.com>
>> 
>> Commit 5e5019bf removed this kind of error.
>> 
>> But we've already protected race condition by qemuDomainObjEnterAgent,
>> it was very unlikely to revieve a sync from other calls.
>> For call from virDomain*, it's better to show this error
>> if we really got a mismatch sync.
>
>Hi, Chen. 
>
>We've observed such condition on practice. So if you report error in this
>place then agent monitor will enter error state and will become unusable
>and there are no means to leave this state other then restarting libvirtd
>AFAIK. Even if there is a option to reset monitor then client will reset
>it by itself on receiving VIR_ERR_AGENT_UNSYNCED error. But then why enter
>error state in this case?
>

Hi, Nikolay 
 
My concern is that the mismatch of sync id informs qga is malfunctioning.
If in that state, we SHOULD set agent monitor to error state,
we'll get VIR_ERR_AGENT_UNRESPONSIVE.

The sysadmin should notice this, and login to VMs to do something.

Restarting qga inside guest will reset the monitor's agentError,
maybe malfunction of qga will be reset at the same time.

Regards,
- Chen