RE: [RFC PATCH 1/4] net/awd.c: Introduce Advanced Watch Dog module framework

[Zhang, Chen]

> -----Original Message-----
> From: Paolo Bonzini <address@hidden>
> Sent: Tuesday, October 22, 2019 1:24 AM
> To: Zhang, Chen <address@hidden>; Jason Wang
> <address@hidden>; qemu-dev <address@hidden>
> Cc: Zhang Chen <address@hidden>
> Subject: Re: [RFC PATCH 1/4] net/awd.c: Introduce Advanced Watch Dog
> module framework
> 
> On 16/10/19 13:22, Zhang Chen wrote:
> > From: Zhang Chen <address@hidden>
> >
> > This patch introduce a new module named Advanced Watch Dog, and
> > defined the input and output parameter. AWD use standard chardev as
> > the way of communicationg with the outside world. Demo command:
> > -object
> > advanced-
> watchdog,id=heart1,server=on,awd_node=h1,notification_node=he
> > artbeat0,opt_script=opt_script_path,iothread=iothread1,pulse_interval=
> > 1000,timeout=5000
> Is there a standard or specification for how to interact with this?  Is this
> something that was developed explicitly for these patches, or did it exist
> before?
> 

Hi Paolo,

Thanks you for your attention.
Current AWD patch just accept any input as the signal to refresh the watchdog 
timer,
and we can also make a certain interactive protocol here. For the output user 
can pre-write
some command or some messages in the AWD opt-script. We noticed that there is 
no way
for VMM communicate directly, maybe some people think we don't need such 
things(up layer
software like openstack can handle it). But we engaged with real customer found 
that in some cases,
they need a lightweight and efficient mechanism to solve some practical 
problems(openstack is too heavy).
For example in COLO (https://wiki.qemu.org/Features/COLO).
We need heartbeat service to detect two node status, current implement need 
another application
running in the host to do this job, if found issue it will send message to 
local Qemu by qmp command,
This is very complicated in actual scenarios, we have to bind each heartbeat 
service with
the VM instance and handle lots of internal errors. Advanced watch dog can 
solve this issue in most cases.
At the same time, AWD also can be used in a variety of scenarios, it can active 
detect Qemu status and 
do some simple automatic processing for example kill itself when it loss 
control with openstack(just need simple paired service). 
 

Thanks
Zhang Chen

> Paolo