Re: [Qemu-block] question： Does qemu-pr-helper have its own log files？

[Stefan Hajnoczi]

On Wed, Apr 24, 2019 at 02:37:36AM +0000, Zhangbo (Oscar) wrote:
> >From: Stefan Hajnoczi [mailto:address@hidden
> >Sent: Tuesday, April 23, 2019 9:57 PM
> >On Tue, Apr 23, 2019 at 11:12:40AM +0800, Jie Wang wrote:
> >>  Does qemu-pr-helper have its own log files？
> >
> >No, it does not.  qemu-pr-helper uses stderr for errors and there is not
> >much output during normal operation.
> >
> >Check journalctl(1) for errors if you are launching it as a systemd
> >service.
> >
> >Stefan
> 
> The error messages that sent to *stderr* are *not* captured by anyone, then
> these error messages seems helpless.

This depends on how qemu-pr-helper was launched.

Daniel Berrange mentioned that stderr is not captured when libvirt
launches qemu-pr-helper.  So in this case there is a problem.

> It's different form qemu's log,  qemu's stderr logs are transferred to 
> virtlogd,
> that means these logs are finally written into disk.
> Any further development plan?
> 
> We thought of:
> 1 logging into syslog, but the malicious guest may cause large amount of error
>   messages to overflow the message log.
> 2 or, let virtlogd to redirect its logs. But if virtlogd get restarted, the 
> helper's log would
>   no longer be logged, because, unlike qemu, there's no qmp socket between 
>   libvirtd and the helper, the channel between the helper and virtlogd could 
> not be
>   re-established.
> 3 or, let qemu to log the helper's log, seems a little odd and complex.
> 4 or, let the helper realize its own logging scheme and log into itself's 
> logfile ?

Perhaps libvirt should be modified to handle stderr.

Stefan

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