[Gluster-devel] Query regards to heal xattr heal in dht

[Mohit Agrawal]

Hi All,

   I have upload a new patch (http://review.gluster.org/#/c/15456/),Please
do the code review.

Regards
Mohit Agrawal


On Thu, Sep 8, 2016 at 12:02 PM, Mohit Agrawal <moagrawa at redhat.com> wrote:

> Hi All,
>
>    I have one another solution to heal user xattr but before implement it
> i would like to discuss with you.
>
>    Can i call function (dht_dir_xattr_heal internally it is calling
> syncop_setxattr) to heal xattr in dht_getxattr_cbk in last
>    after make sure we have a valid xattr.
>    In function(dht_dir_xattr_heal) it will copy blindly all user xattr on
> all subvolume or i can compare subvol xattr with valid xattr if there is
> any mismatch then i will call syncop_setxattr otherwise no need to call.
> syncop_setxattr.
>
>    Let me know if this approach is suitable.
>
>
>
> Regards
> Mohit Agrawal
>
> On Wed, Sep 7, 2016 at 10:27 PM, Pranith Kumar Karampuri <
> pkarampu at redhat.com> wrote:
>
>>
>>
>> On Wed, Sep 7, 2016 at 9:46 PM, Mohit Agrawal <moagrawa at redhat.com>
>> wrote:
>>
>>> Hi Pranith,
>>>
>>>
>>> In current approach i am getting list of xattr from first up volume and
>>> update the user attributes from that xattr to
>>> all other volumes.
>>>
>>> I have assumed first up subvol is source and rest of them are sink as we
>>> are doing same in dht_dir_attr_heal.
>>>
>>
>> I think first up subvol is different for different mounts as per my
>> understanding, I could be wrong.
>>
>>
>>>
>>> Regards
>>> Mohit Agrawal
>>>
>>> On Wed, Sep 7, 2016 at 9:34 PM, Pranith Kumar Karampuri <
>>> pkarampu at redhat.com> wrote:
>>>
>>>> hi Mohit,
>>>>        How does dht find which subvolume has the correct list of
>>>> xattrs? i.e. how does it determine which subvolume is source and which is
>>>> sink?
>>>>
>>>> On Wed, Sep 7, 2016 at 2:35 PM, Mohit Agrawal <moagrawa at redhat.com>
>>>> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>>   I am trying to find out solution of one problem in dht specific to
>>>>> user xattr healing.
>>>>>   I tried to correct it in a same way as we are doing for healing dir
>>>>> attribute but i feel it is not best solution.
>>>>>
>>>>>   To find a right way to heal xattr i want to discuss with you if
>>>>> anyone does have better solution to correct it.
>>>>>
>>>>>   Problem:
>>>>>    In a distributed volume environment custom extended attribute value
>>>>> for a directory does not display correct value after stop/start the brick.
>>>>> If any extended attribute value is set for a directory after stop the brick
>>>>> the attribute value is not updated on brick after start the brick.
>>>>>
>>>>>   Current approach:
>>>>>     1) function set_user_xattr to store user extended attribute in
>>>>> dictionary
>>>>>     2) function dht_dir_xattr_heal call syncop_setxattr to update the
>>>>> attribute on all volume
>>>>>     3) Call the function (dht_dir_xattr_heal) for every directory
>>>>> lookup in dht_lookup_revalidate_cbk
>>>>>
>>>>>   Psuedocode for function dht_dir_xatt_heal is like below
>>>>>
>>>>>    1) First it will fetch atttributes from first up volume and store
>>>>> into xattr.
>>>>>    2) Run loop on all subvolume and fetch existing attributes from
>>>>> every volume
>>>>>    3) Replace user attributes from current attributes with xattr user
>>>>> attributes
>>>>>    4) Set latest extended attributes(current + old user attributes)
>>>>> inot subvol.
>>>>>
>>>>>
>>>>>    In this current approach problem is
>>>>>
>>>>>    1) it will call heal function(dht_dir_xattr_heal) for every
>>>>> directory lookup without comparing xattr.
>>>>>     2) The function internally call syncop xattr for every subvolume
>>>>> that would be a expensive operation.
>>>>>
>>>>>    I have one another way like below to correct it but again in this
>>>>> one it does have dependency on time (not sure time is synch on all bricks
>>>>> or not)
>>>>>
>>>>>    1) At the time of set extended attribute(setxattr) change time in
>>>>> metadata at server side
>>>>>    2) Compare change time before call healing function in
>>>>> dht_revalidate_cbk
>>>>>
>>>>>     Please share your input on this.
>>>>>     Appreciate your input.
>>>>>
>>>>> Regards
>>>>> Mohit Agrawal
>>>>>
>>>>> _______________________________________________
>>>>> Gluster-devel mailing list
>>>>> Gluster-devel at gluster.org
>>>>> http://www.gluster.org/mailman/listinfo/gluster-devel
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Pranith
>>>>
>>>
>>>
>>
>>
>> --
>> Pranith
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.gluster.org/pipermail/gluster-devel/attachments/20160911/56a42e0d/attachment.html>