[Gluster-users] Fwd: bug in 3.4.1 when creating symlinks

Wed Nov 13 20:14:14 UTC 2013

Thanks for taking the time to look at this and reply.  To clarify, the
script that was running and created the log entries is an internal tool
which does lots of other, unrelated things, but the part that caused the
error takes actions very similar to the gist.  I tried to pull out the
related log entries to the best of my ability.  The script in the gist did
not create those log entries, but it does reliably reproduce the same error
/ failure (failure when attempting to create a symlink from the local
filesystem to a symlink on the gluster filesystem).  I would not be
surprised if the PHP version of symlink has behavior that is different than
the symlink syscall.

On Wed, Nov 13, 2013 at 2:34 PM, Anand Avati <avati at gluster.org> wrote:

>
>
>
> On Wed, Nov 13, 2013 at 9:01 AM, Peter Drake <peter.drake at acquia.com>wrote:
>
>> I have a replicated Gluster setup, 2 servers (fs-1 and fs-2) x 1 brick.
>>  I have two clients (web-1 and web-2) which are connected and
>> simultaneously execute tasks.  These clients mount the Gluster volume at
>> /mnt/gfs.  One task they execute looks like this (note this is pseudocode,
>> the actual task is PHP):
>>
>> 1. @symlink(/mnt/gfs/slow265, /mnt/gfs/slow265.prod);
>> 2. if (!is_link(/mnt/gfs/slow265.prod)) {
>> 3.   throw Exception;
>> 4. }
>> 5. symlink(/mnt/gfs/slow265.prod, /home/user/slow265.prod)
>>
>> Note that line 1 may fail on either client because the link may have been
>> created by the other client, but this is suppressed, the link is checked
>> and an exception is thrown if the link does not exist.  These two tasks,
>> when executed at the same time, usually succeed.  However, in a recent run,
>> we saw an error on web-1 in line 5 because the local filesystem symlink
>> creation failed, despite line 2 confirming that the target Gluster symlink
>> existed.
>>
>
> This is strange. The creation of a symlink is completely independent of
> whether the destination exists, readable, or whatever. If creation of a
> symlink failed, it cannot be because of anything to do with the
> destination. Unless symlink() of PHP does something "intelligent" and makes
> it behave differently than symlink(2) syscall.
>
>
>
>> I've created a PHP script which can be run simultaneously on two clients
>> to recreate the error: https://gist.github.com/pdrakeweb/7347198
>>
>> Running the same test script on a Gluster 3.0.8 setup does not cause the
>> error to occur.  Running the same test on a local-only filesystem also does
>> not cause the error to occur.  I'd appreciate any insight people might have
>> into what is going on here and whether this is a bug in 3.4.1.  Below are
>> the related log entries from my Gluster servers and clients.
>>
>> Entries from web-1's mnt-gfs.log file:
>>
>> [2013-11-05 05:25:24.686506] W [client-rpc-fops.c:259:client3_3_mknod_cbk] 0-test-fs-cluster-1-client-1: remote operation failed: File exists. Path: /slow265.prod (00000000-0000-0000-0000-000000000000)
>> [2013-11-05 05:25:24.686584] W [client-rpc-fops.c:259:client3_3_mknod_cbk] 0-test-fs-cluster-1-client-0: remote operation failed: File exists. Path: /slow265.prod (00000000-0000-0000-0000-000000000000)
>>
>>
> So, slow265.prod is supposed to be a symlink? I really wonder why mknod()
> is in the picture.
>
>
>> [2013-11-05 05:25:24.686649] E [dht-helper.c:1052:dht_inode_ctx_get] (-->/usr/lib/x86_64-linux-gnu/glusterfs/3.4git/xlator/cluster/distribute.so(dht_lookup_linkfile_create_cbk+0x75) [0x7f5e03dd4ff5] (-->/usr/lib/x86_64-linux-gnu/glusterfs/3.4git/xlator/cluster/distribute.so(dht_layout_preset+0x59) [0x7f5e03dc1c89] (-->/usr/lib/x86_64-linux-gnu/glusterfs/3.4git/xlator/cluster/distribute.so(dht_inode_ctx_layout_set+0x34) [0x7f5e03dc3b34]))) 0-test-fs-cluster-1-dht: invalid argument: inode
>> [2013-11-05 05:25:24.686687] E [dht-helper.c:1071:dht_inode_ctx_set] (-->/usr/lib/x86_64-linux-gnu/glusterfs/3.4git/xlator/cluster/distribute.so(dht_lookup_linkfile_create_cbk+0x75) [0x7f5e03dd4ff5] (-->/usr/lib/x86_64-linux-gnu/glusterfs/3.4git/xlator/cluster/distribute.so(dht_layout_preset+0x59) [0x7f5e03dc1c89] (-->/usr/lib/x86_64-linux-gnu/glusterfs/3.4git/xlator/cluster/distribute.so(dht_inode_ctx_layout_set+0x52) [0x7f5e03dc3b52]))) 0-test-fs-cluster-1-dht: invalid argument: inode
>> [2013-11-05 05:25:24.689670] W [fuse-bridge.c:1311:fuse_readlink_cbk] 0-glusterfs-fuse: 1736: /slow265.prod => -1 (Invalid argument)
>>
>>
>> Entries from web-2's mnt-gfs.log file:
>>
>> [2013-11-05 05:25:26.164593] W [client-rpc-fops.c:2469:client3_3_link_cbk] 0-test-fs-cluster-1-client-1: remote operation failed: File exists (00000000-0000-0000-0000-000000000000 -> /slow265.prod)
>>
>>
> client3_3_link_cbk is the callback for the link() hardlink system call.
> Wonder why that is coming in the picture! Neither should mknod(). Going by
> your script, the only calls should be SYMLINK, LOOKUP and READLINK.
>
>
>> [2013-11-05 05:25:26.210652] W [client-rpc-fops.c:2469:client3_3_link_cbk] 0-test-fs-cluster-1-client-0: remote operation failed: File exists (00000000-0000-0000-0000-000000000000 -> /slow265.prod)
>>
>>
>> Entries from fs-1's brick.log:
>>
>> [2013-11-05 05:25:24.832262] I [server-rpc-fops.c:575:server_mknod_cbk] 0-test-fs-cluster-1-server: 3337: MKNOD (null) (00000000-0000-0000-0000-000000000001/slow265.prod) ==> (File exists)
>>
>> [2013-11-05 05:25:26.391611] I [server-rpc-fops.c:1211:server_link_cbk] 0-test-fs-cluster-1-server: 3301: LINK /slow265.prod (3658314e-7730-4771-8ac3-2d6fb20b1b13) -> 00000000-0000-0000-0000-000000000001/slow265.prod ==> (File exists)
>>
>>
>>
>>
>>
>> Entries from fs-2's brick.log:
>>
>> [2013-11-05 05:25:24.554824] I [server-rpc-fops.c:575:server_mknod_cbk] 0-test-fs-cluster-1-server: 3290: MKNOD (null) (00000000-0000-0000-0000-000000000001/slow265.prod) ==> (File exists)
>>
>> [2013-11-05 05:25:26.160204] I [server-rpc-fops.c:1211:server_link_cbk] 0-test-fs-cluster-1-server: 3341: LINK /slow265.prod (3658314e-7730-4771-8ac3-2d6fb20b1b13) -> 00000000-0000-0000-0000-000000000001/slow265.prod ==> (File exists)
>>
>>
> Again, LINK is a hardlink call. Not sure why that is coming into the
> picture. Is slow265 supposed to be a symlink or a hardlink?
>
> Is rename() somehow involved? I don't see any rename() calls in your
> script.
>
> With the info you have given above, all I can say is: either the script in
> gist did not create the above logs, or PHP does something really really
> weird under the hoods. Is it possible to give the strace logs on the script
> while it executed? That should clarify a lot of things..
>
> Avati
>
>

-- 
*Peter Drake *|* Cloud Software Engineer* |  Acquia <http://acquia.com/>

O: 781.238.4236

*E:* peter.drake at acquia.com  |  Skype: pdrakeweb

W: http://www.acquia.com <http://www.acquia.com/>

Address: 25 Corporate Drive 4th Floor, Burlington, MA 01803

Acquia ranked #1 Software Vendor on the 2012 Inc
500<http://www.acquia.com/about-us/newsroom/press-releases/inc-magazine-unveils-31st-annual-list-america-s-fastest-growing>

Acquia named One of America’s Most Promising Companies by
Forbes<http://www.acquia.com/about-us/newsroom/press-releases/acquia-named-forbes-100-list-america-s-most-promising-companies-nov>

Drupal Sites: http://drupalshowcase.com
Twitter http://www.twitter.com/Acquia
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://supercolony.gluster.org/pipermail/gluster-users/attachments/20131113/002206c8/attachment.html>