[Gluster-users] question about info and info.tmp

Fri Nov 11 07:08:57 UTC 2016

Hi Atin,
Thank you for your reply.

As you said that the info file can only be changed in the glusterd_store_volinfo() sequentially because of the big lock.

I have found the similar issue as below that you mentioned. 
https://bugzilla.redhat.com/show_bug.cgi?id=1308487

You said that "This issue is hit at part of the negative testing where while gluster volume set was executed at the same point of time glusterd in another instance was brought down. In the faulty node we could see /var/lib/glusterd/vols/<volname>info file been empty whereas the info.tmp file has the correct contents." in comment.

I have two questions for you.

1.Could you reproduce this issue by gluster volume set glusterd which was brought down?
2.Could you be certain that this issue is cause by rename is interrupted in kernel?

In my case there are two files, info and 10.32.1.144.-opt-lvmdir-c2-brick, are both empty.
But in my view only one rename can be running at the same time because of the big lock.
Why there are two files are empty?

Could rename("info.tmp", "info") and rename("xxx-brick.tmp", "xxx-brick") be running in two thread?

Thanks,
Xin

在 2016-11-11 14:36:40，"Atin Mukherjee" <amukherj at redhat.com> 写道：

On Fri, Nov 11, 2016 at 8:33 AM, songxin <songxin_1980 at 126.com> wrote:

Hi Atin,

Thank you for your reply.
I have two questions for you.

1.Are the two files info and info.tmp are only to be created or changed in function glusterd_store_volinfo()? I did not find other point in which the two file are changed.

If we are talking about info file volume then yes, the mentioned function actually takes care of it.

2.I found that glusterd_store_volinfo() will be call in many point by glusterd.Is there a problem of thread synchronization?If so, one thread may open a same file info.tmp using O_TRUNC flag when another thread is writing the info,tmp.Could this case happen?

 In glusterd threads are big lock protected and I don't see a possibility (theoretically) to have two glusterd_store_volinfo () calls at a given point of time.

Thanks,
Xin

At 2016-11-10 21:41:06, "Atin Mukherjee" <amukherj at redhat.com> wrote:

Did you run out of disk space by any chance? AFAIK, the code is like we write new stuffs to .tmp file and rename it back to the original file. In case of a disk space issue I expect both the files to be of non zero size. But having said that I vaguely remember a similar issue (in the form of a bug or an email) landed up once but we couldn't reproduce it, so something is wrong with the atomic update here is what I guess. I'll be glad if you have a reproducer for the same and then we can dig into it further.

On Thu, Nov 10, 2016 at 1:32 PM, songxin <songxin_1980 at 126.com> wrote:

Hi,
When I start the glusterd some error happened.
And the log is following.

[2016-11-08 07:58:34.989365] I [MSGID: 100030] [glusterfsd.c:2318:main] 0-/usr/sbin/glusterd: Started running /usr/sbin/glusterd version 3.7.6 (args: /usr/sbin/glusterd -p /var/run/glusterd.pid --log-level INFO) 
[2016-11-08 07:58:34.998356] I [MSGID: 106478] [glusterd.c:1350:init] 0-management: Maximum allowed open file descriptors set to 65536 
[2016-11-08 07:58:35.000667] I [MSGID: 106479] [glusterd.c:1399:init] 0-management: Using /system/glusterd as working directory
[2016-11-08 07:58:35.024508] I [MSGID: 106514] [glusterd-store.c:2075:glusterd_restore_op_version] 0-management: Upgrade detected. Setting op-version to minimum : 1 
[2016-11-08 07:58:35.025356] E [MSGID: 106206] [glusterd-store.c:2562:glusterd_store_update_volinfo] 0-management: Failed to get next store iter 
[2016-11-08 07:58:35.025401] E [MSGID: 106207] [glusterd-store.c:2844:glusterd_store_retrieve_volume] 0-management: Failed to update volinfo for c_glusterfs volume 
[2016-11-08 07:58:35.025463] E [MSGID: 106201] [glusterd-store.c:3042:glusterd_store_retrieve_volumes] 0-management: Unable to restore volume: c_glusterfs 
[2016-11-08 07:58:35.025544] E [MSGID: 101019] [xlator.c:428:xlator_init] 0-management: Initialization of volume 'management' failed, review your volfile again 
[2016-11-08 07:58:35.025582] E [graph.c:322:glusterfs_graph_init] 0-management: initializing translator failed 
[2016-11-08 07:58:35.025629] E [graph.c:661:glusterfs_graph_activate] 0-graph: init failed 
[2016-11-08 07:58:35.026109] W [glusterfsd.c:1236:cleanup_and_exit] (-->/usr/sbin/glusterd(glusterfs_volumes_init-0x1b260) [0x1000a718] -->/usr/sbin/glusterd(glusterfs_process_volfp-0x1b3b8) [0x1000a5a8] -->/usr/sbin/glusterd(cleanup_and_exit-0x1c02c) [0x100098bc] ) 0-: received signum (0), shutting down 

And then I found that the size of vols/volume_name/info is 0.It cause glusterd shutdown.
But I found that vols/volume_name_info.tmp is not 0.
And I found that there is a brick file vols/volume_name/bricks/xxxx.brick is 0, but vols/volume_name/bricks/xxxx.brick.tmp is not 0.

I read the function code glusterd_store_volinfo () in glusterd-store.c .
I know that the info.tmp will be rename to info in function glusterd_store_volume_atomic_update().

But my question is that why the info file is 0 but info.tmp is not 0.

Thanks,
Xin

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~ Atin (atinm)

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~ Atin (atinm)
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