[libvirt] [PATCH] libxl: Create per-domain log file

[Eric Blake]

On 08/09/2013 11:04 AM, Daniel P. Berrange wrote:
> On Fri, Aug 09, 2013 at 10:56:41AM -0600, Eric Blake wrote:
>> On 08/09/2013 10:50 AM, Daniel P. Berrange wrote:
>>
>>>> I should have looked at the xen code closer.  Seems libxl doesn't cope
>>>> well with a NULL logger :(.
>>>>
>>>> Hmm, should the logger for this driver-wide ctx (used for getting libxl
>>>> version and the like, no domain ops) just dump messages to /dev/null or
>>>> should they go to a driver-wide log file?
>>>
>>> Depends if you think there's any useful info to be had from the
>>> driver wide context object ? If so, then probably best to have a
>>> driver-wide log file for those messages
>>
>> Or even just reply the data into the main libvirtd.log (ie. use existing
>> virLog functionality, rather than creating a new file), since ideally
>> the log will be relatively sparse: in my case, it would be just one
>> message stating that libxl is not available, at which point the libxl
>> driver no longer does anything else during the life of libvirtd.
> 
> I was going to suggest that, but IIUC, the libxl logger API requires
> you to give it a FILE * instance to which it writes directly. To feed
> it into our normal logs, we'd want it to let us give it a callback
> for writing log messages.

Can we rely on open_memstream() being present on any platform with
libxl?  If so, that would give us a FILE* interface to libxl, while
still giving us access to the strings it prints which we can then turn
around and hand to our logger.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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