[Gluster-devel] Consistent time attributes (ctime, atime and mtime) across replica set and distribution set

[Amar Tumballi]

On Thu, Mar 16, 2017 at 6:52 AM, Soumya Koduri <skoduri at redhat.com> wrote:

>
>
> On 03/16/2017 02:27 PM, Mohammed Rafi K C wrote:
>
>>
>>
>> On 03/15/2017 11:31 PM, Soumya Koduri wrote:
>>
>>> Hi Rafi,
>>>
>>> I haven't thoroughly gone through design. But have few
>>> comments/queries which I have posted inline for now .
>>>
>>> On 02/28/2017 01:11 PM, Mohammed Rafi K C wrote:
>>>
>>>> Thanks for the reply , Comments are inline
>>>>
>>>>
>>>>
>>>> On 02/28/2017 12:50 PM, Niels de Vos wrote:
>>>>
>>>>> On Tue, Feb 28, 2017 at 11:21:55AM +0530, Mohammed Rafi K C wrote:
>>>>>
>>>>>> Hi All,
>>>>>>
>>>>>>
>>>>>> We discussed the problem $subject in the mail thread [1]. Based on the
>>>>>> comments and suggestions I will summarize the design (Made as
>>>>>> points for
>>>>>> simplicity.)
>>>>>>
>>>>>>
>>>>>> 1) As part of each fop, top layer will generate a time stamp and
>>>>>> pass it
>>>>>> to the down along with other param.
>>>>>>
>>>>>>     1.1) This will bring a dependency for NTP synced clients along
>>>>>> with
>>>>>> servers
>>>>>>
>>>>> What do you mean with "top layer"? Is this on the Gluster client, or
>>>>> does the time get inserted on the bricks?
>>>>>
>>>> It is the top layer (master xlator) in client graph like fuse, gfapi,
>>>> nfs . My mistake I should have mentioned . Sorry for that.
>>>>
>>>
>>> These clients shouldn't include internal client processes like
>>> rebalance, self-heal daemons right? IIUC from [1], we should avoid
>>> changing times during rebalance and self-heals.
>>>
>>> Also what about fops generated from the underlying layers -
>>> getxattr/setxattr which may modify these time attributes?
>>>
>>
>> Since the time stamps are appended from master xlators like fuse , we
>> will not have the timestamp for internal daemons as they don't have
>> master xlator loaded. internal fops won't generate new timestamp , even
>> if we are sending an internal fops from say dht, it will have only one
>> time genrated by fuse. So I think this is fine.
>>
>
> Okay. But since self-heal and snapview-server (atleast) seem to be using
> gfapi, how can gfapi differentiate between these internal clients and other
> applications (like NFS/SMB)? I thought we need intelligence on server-side
> to identify such clients based on pid and then avoid updating timestamp
> sent by them.
>
>
Very good point. Considering we should be using gfapi in future for most of
the internal processes, this becomes more important. Should we just add it
as argument to glfs_init() options? If you set a flag during init, the
ctime xattr is not generated for the fops which otherwise generate and send
them.

-Amar



>
> Thanks,
> Soumya
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-- 
Amar Tumballi (amarts)
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