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

Mohit Agrawal moagrawa at redhat.com
Thu Sep 8 06:32:31 UTC 2016

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.

   Let me know if this approach is suitable.

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
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