Re: Sharding problem - multiple shard copies with mismatching gfids

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Raghavenda,

The issue typically appears during heavy write operations to the VM image. Its most noticeable during the filesystem creation process on a virtual machine image. I'll get some specific data while executing that process and will get back to you soon.

thanks


-- Ian

------ Original Message ------
From: "Raghavendra Gowdappa" <rgowdapp@xxxxxxxxxx>
To: "Krutika Dhananjay" <kdhananj@xxxxxxxxxx>
Cc: "Ian Halliday" <ihalliday@xxxxxxxxxx>; "gluster-user" <gluster-users@xxxxxxxxxxx>; "Nithya Balachandran" <nbalacha@xxxxxxxxxx>
Sent: 3/26/2018 2:37:21 AM
Subject: Re: Sharding problem - multiple shard copies with mismatching gfids

Ian,

Do you've a reproducer for this bug? If not a specific one, a general outline of what operations where done on the file will help.

regards,
Raghavendra

On Mon, Mar 26, 2018 at 12:55 PM, Raghavendra Gowdappa <rgowdapp@xxxxxxxxxx> wrote:


On Mon, Mar 26, 2018 at 12:40 PM, Krutika Dhananjay <kdhananj@xxxxxxxxxx> wrote:
The gfid mismatch here is between the shard and its "link-to" file, the creation of which happens at a layer below that of shard translator on the stack.

Adding DHT devs to take a look.

Thanks Krutika. I assume shard doesn't do any dentry operations like rename, link, unlink on the path of file (not the gfid handle based path) internally while managing shards. Can you confirm? If it does these operations, what fops does it do?

@Ian,

I can suggest following way to fix the problem:
* Since one of files listed is a DHT linkto file, I am assuming there is only one shard of the file. If not, please list out gfids of other shards and don't proceed with healing procedure.
* If gfids of all shards happen to be same and only linkto has a different gfid, please proceed to step 3. Otherwise abort the healing procedure.
* If cluster.lookup-optimize is set to true abort the healing procedure
* Delete the linkto file - the file with permissions -------T and xattr trusted.dht.linkto and do a lookup on the file from mount point after turning off readdriplus [1].

As to reasons on how we ended up in this situation, Can you explain me what is the I/O pattern on this file - like are there lots of entry operations like rename, link, unlink etc on the file? There have been known races in rename/lookup-heal-creating-linkto where linkto and data file have different gfids. [2] fixes some of these cases


regards,
Raghavendra


-Krutika

On Mon, Mar 26, 2018 at 1:09 AM, Ian Halliday <ihalliday@xxxxxxxxxx> wrote:
Hello all,

We are having a rather interesting problem with one of our VM storage systems. The GlusterFS client is throwing errors relating to GFID mismatches. We traced this down to multiple shards being present on the gluster nodes, with different gfids.

Hypervisor gluster mount log:

[2018-03-25 18:54:19.261733] E [MSGID: 133010] [shard.c:1724:shard_common_lookup_shards_cbk] 0-ovirt-zone1-shard: Lookup on shard 7 failed. Base file gfid = 87137cac-49eb-492a-8f33-8e33470d8cb7 [Stale file handle]
The message "W [MSGID: 109009] [dht-common.c:2162:dht_lookup_linkfile_cbk] 0-ovirt-zone1-dht: /.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7: gfid different on data file on ovirt-zone1-replicate-3, gfid local = 00000000-0000-0000-0000-000000000000, gfid node = 57c6fcdf-52bb-4f7a-aea4-02f0dc81ff56 " repeated 2 times between [2018-03-25 18:54:19.253748] and [2018-03-25 18:54:19.263576]
[2018-03-25 18:54:19.264349] W [MSGID: 109009] [dht-common.c:1901:dht_lookup_everywhere_cbk] 0-ovirt-zone1-dht: /.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7: gfid differs on subvolume ovirt-zone1-replicate-3, gfid local = fdf0813b-718a-4616-a51b-6999ebba9ec3, gfid node = 57c6fcdf-52bb-4f7a-aea4-02f0dc81ff56


On the storage nodes, we found this:

[root@n1 gluster]# find -name 87137cac-49eb-492a-8f33-8e33470d8cb7.7
./brick2/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7
./brick4/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7

[root@n1 gluster]# ls -lh ./brick2/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7
---------T. 2 root root 0 Mar 25 13:55 ./brick2/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7
[root@n1 gluster]# ls -lh ./brick4/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7
-rw-rw----. 2 root root 3.8G Mar 25 13:55 ./brick4/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7

[root@n1 gluster]# getfattr -d -m . -e hex ./brick2/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7
# file: brick2/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7
security.selinux=0x73797374656d5f753a6f626a6563745f723a756e6c6162656c65645f743a733000
trusted.gfid=0xfdf0813b718a4616a51b6999ebba9ec3
trusted.glusterfs.dht.linkto=0x6f766972742d3335302d7a6f6e65312d7265706c69636174652d3300

[root@n1 gluster]# getfattr -d -m . -e hex ./brick4/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7
# file: brick4/brick/.shard/87137cac-49eb-492a-8f33-8e33470d8cb7.7
security.selinux=0x73797374656d5f753a6f626a6563745f723a756e6c6162656c65645f743a733000
trusted.afr.dirty=0x000000000000000000000000
trusted.bit-rot.version=0x020000000000000059914190000ce672
trusted.gfid=0x57c6fcdf52bb4f7aaea402f0dc81ff56


I'm wondering how they got created in the first place, and if anyone has any insight on how to fix it?

Storage nodes:
[root@n1 gluster]# gluster --version
glusterfs 4.0.0

[root@n1 gluster]# gluster volume info

Volume Name: ovirt-350-zone1
Type: Distributed-Replicate
Volume ID: 106738ed-9951-4270-822e-63c9bcd0a20e
Status: Started
Snapshot Count: 0
Number of Bricks: 7 x (2 + 1) = 21
Transport-type: tcp
Bricks:
Brick1: 10.0.6.100:/gluster/brick1/brick
Brick2: 10.0.6.101:/gluster/brick1/brick
Brick3: 10.0.6.102:/gluster/arbrick1/brick (arbiter)
Brick4: 10.0.6.100:/gluster/brick2/brick
Brick5: 10.0.6.101:/gluster/brick2/brick
Brick6: 10.0.6.102:/gluster/arbrick2/brick (arbiter)
Brick7: 10.0.6.100:/gluster/brick3/brick
Brick8: 10.0.6.101:/gluster/brick3/brick
Brick9: 10.0.6.102:/gluster/arbrick3/brick (arbiter)
Brick10: 10.0.6.100:/gluster/brick4/brick
Brick11: 10.0.6.101:/gluster/brick4/brick
Brick12: 10.0.6.102:/gluster/arbrick4/brick (arbiter)
Brick13: 10.0.6.100:/gluster/brick5/brick
Brick14: 10.0.6.101:/gluster/brick5/brick
Brick15: 10.0.6.102:/gluster/arbrick5/brick (arbiter)
Brick16: 10.0.6.100:/gluster/brick6/brick
Brick17: 10.0.6.101:/gluster/brick6/brick
Brick18: 10.0.6.102:/gluster/arbrick6/brick (arbiter)
Brick19: 10.0.6.100:/gluster/brick7/brick
Brick20: 10.0.6.101:/gluster/brick7/brick
Brick21: 10.0.6.102:/gluster/arbrick7/brick (arbiter)
Options Reconfigured:
cluster.min-free-disk: 50GB
performance.strict-write-ordering: off
performance.strict-o-direct: off
nfs.disable: off
performance.readdir-ahead: on
transport.address-family: inet
performance.cache-size: 1GB
features.shard: on
features.shard-block-size: 5GB
server.event-threads: 8
server.outstanding-rpc-limit: 128
storage.owner-uid: 36
storage.owner-gid: 36
performance.quick-read: off
performance.read-ahead: off
performance.io-cache: off
performance.stat-prefetch: on
cluster.eager-lock: enable
network.remote-dio: enable
cluster.quorum-type: auto
cluster.server-quorum-type: server
cluster.data-self-heal-algorithm: full
performance.flush-behind: off
performance.write-behind-window-size: 8MB
client.event-threads: 8
server.allow-insecure: on


Client version: 
[root@kvm573 ~]# gluster --version
glusterfs 3.12.5


Thanks!

- Ian


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