[CRIU] [PATCH] stats/pid-reuse: put stats to image directory instead of cwd

[Pavel Tikhomirov]

On 03/26/2018 02:19 PM, Pavel Emelyanov wrote:
> On 03/26/2018 02:02 PM, Cyrill Gorcunov wrote:
>> On Mon, Mar 26, 2018 at 01:43:11PM +0300, Pavel Emelyanov wrote:
>>> On 03/26/2018 12:16 PM, Pavel Tikhomirov wrote:
>>>> On 03/26/2018 11:54 AM, Pavel Emelyanov wrote:
>>>>> On 03/26/2018 11:12 AM, Pavel Tikhomirov wrote:
>>>>>> Statistics for a special dump/pre-dump/restore action should be
>>>>>> collected in the images directory of these action. We need these for
>>>>>> pid-reuse detection as we need to read the stats of parent predump.
>>>>>
>>>>> What's wrong with checking pid-reuse form stats sitting in workdir?
>>>>
>>>> We can read previous dump statistics from workdir before
>>>> cr_*dump_finish, I agree with that, it is easy.
>>>>
>>>> But Kirill says that "writing image outside of image directory is
>>>
>>> Stats file is not an image. We just use PB format for it and reuse existing
>>> image-writing machinery.
>>
>> Stats file is context dependant and logically bound to images. At least
>> keeping it inside image drectory gives you confidence the data written
>> there belongs exactly to the images produced.
> 
> So are logs, but we keep them in workdir anyway.
> 
>> Because pid reuse uses
>> data from stats to operate on memory engine it become not longer
>> a random stat just to view, but mandatory data required for proper
>> restore.
> 
> I've missed that fast somehow. What's there in stats image the pid-reuse needs?

StatsEntry->dump->dump_uptime

> 
>> If you still prefer stats file to be on its own then I think we
>> need use some other image to carry this information.
>>
>>>> architectural problem", actually I think these way too for at least two
>>>> reasons:
>>>>
>>>> 1) When stats image is in images dir we can latter analize stats for
>>>> each iteration if we want it. Now doing migration in VZ7 we have only
>>>> stats of last dump in the end.
>>>
>>> The same problem's for log files (I hope nobody has moved them into images dir
>>> so far), isn't it? Use separate workdir for each iteration.
>>
>> Exactly, same problem. And for vz7 the logs are kept in the image
>> directory via vzctl option passed.
> 
> Gents, by default criu keeps work dir and images together, some efforts should be
> done to keep them separately. What option are you talking about?

Likely --log-file is used for logs and for images and workdir: 
--images-dir and --work-dir.

> 
>> Thus when a user comes to us with
>> a problem we ask him to provide us logs from the image directory and
>> if logs on self are not enough we can ask to pack images directory
>> where the *complete* state of everything is present which we need
>> to analyze a problem.
>> .
>>
> 

-- 
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.