I figured out what's happening. The issue is that the file has 'c|a|m' time set to future (The file is created after the date is set to +30 days). This
is done from client-1. On client-2 with correct date, when data is appended, it doesn't update the mtime and ctime because of both mtime and ctime is less than
already set time on the file. This protection is required to keep the latest time when two clients are writing to the same file. We update c|m|a time only if it's greater than
existing time. As a result, the perf xlators on client1 which relies on mtime doesn't send read to server as it thinks nothing is changed as in this case the times haven't
changed.
1. Disabling quick-read solved the issue for me.
The other thing to do is to remove that protection of updating time only if it's greater but that would open up the race when two clients are updating the same file.
Kotresh
Exactly, I am also curious about this. I will debug and update about what's exactly happening.Thanks,
KotreshOn Wed, Mar 11, 2020 at 1:56 PM Zhou, Cynthia (NSB - CN/Hangzhou) <cynthia.zhou@xxxxxxxxxxxxxxx> wrote:I used to think the file is cached in some client side buffer, because I’ve checked from different sn brick, the file content are all correct. But when I open client side trace level log, and cat the file, I only find lookup/open/flush fop from fuse-bridge side, I am just wondering how is file content served to client side? Should not there be readv fop seen from trace log?
cynthia
From: Zhou, Cynthia (NSB - CN/Hangzhou)
Sent: 2020年3月11日 15:54
To: 'Kotresh Hiremath Ravishankar' <khiremat@xxxxxxxxxx>
Subject: RE: could you help to check about a glusterfs issue seems to be related to ctime
Does that require, that for all the time client should be time synched? What if the client time is not synched for a while? And then restored?
I make a test when time has been restored and then client change the file, the file’s modify time, access times remains to be wrong, is that correct?
root@mn-0:/home/robot]
# echo "fromm mn-0">>/mnt/export/testfile
[root@mn-0:/home/robot]
# stat /mnt/export/testfile
File: /mnt/export/testfile
Size: 30 Blocks: 1 IO Block: 131072 regular file
Device: 28h/40d Inode: 9855109080001305442 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 615/_nokfsuifileshare)
Access: 2020-05-10 09:33:59.713840197 +0300
Modify: 2020-05-10 09:33:59.713840197 +0300
Change: 2020-05-10 09:33:59.714413772 +0300 //remains to be future time
Birth: -
[root@mn-0:/home/robot]
# cat /mnt/export/testfil
cat: /mnt/export/testfil: No such file or directory
[root@mn-0:/home/robot]
# cat /mnt/export/testfile
from mn0
from mn-1
fromm mn-0
[root@mn-0:/home/robot]
# date
Wed 11 Mar 2020 09:05:58 AM EET
[root@mn-0:/home/robot]
cynthia
From: Kotresh Hiremath Ravishankar <khiremat@xxxxxxxxxx>
Sent: 2020年3月11日 15:41
To: Zhou, Cynthia (NSB - CN/Hangzhou) <cynthia.zhou@xxxxxxxxxxxxxxx>
Subject: Re: could you help to check about a glusterfs issue seems to be related to ctime
On Wed, Mar 11, 2020 at 12:46 PM Zhou, Cynthia (NSB - CN/Hangzhou) <cynthia.zhou@xxxxxxxxxxxxxxx> wrote:
But there are times that ntp service went wrong, and time on two storage nodes may be not synced.
Or do you mean when can not guarantee that the time on two clients is synched, we should not enable this ctime feature?
Yes, that's correct. The ctime feature relies on the time generated at the client (that's the utime xlator loaded in client) and hence
expects all clients to be ntp synced.
Without ctime feature, is there some way to avoid this “file changed as we read it” issue?
Unfortunately no. That's the only way as of now.
cynthia
From: Kotresh Hiremath Ravishankar <khiremat@xxxxxxxxxx>
Sent: 2020年3月11日 15:12
To: Zhou, Cynthia (NSB - CN/Hangzhou) <cynthia.zhou@xxxxxxxxxxxxxxx>
Subject: Re: could you help to check about a glusterfs issue seems to be related to ctime
Hi,
I have not looked at it. I will take a look and update you. But one of the pre-requisite for ctime feature is that the clients should be time synced (ntp or other means).
Could you try your reproducer by syncing the time of all clients and update me back ?
Thanks,Kotresh HR
On Wed, Mar 11, 2020 at 12:37 PM Zhou, Cynthia (NSB - CN/Hangzhou) <cynthia.zhou@xxxxxxxxxxxxxxx> wrote:
I make some test
After change date to future, and touch a file write sth, then restore time to normal.
Then append sth to the file, the file modify time access time is still future, it is not the same with ext4,
I think this is wrong.
[root@mn-0:/home/robot]
# echo "fromm mn-0">>/mnt/export/testfile
[root@mn-0:/home/robot]
# stat /mnt/export/testfile
File: /mnt/export/testfile
Size: 30 Blocks: 1 IO Block: 131072 regular file
Device: 28h/40d Inode: 9855109080001305442 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 615/_nokfsuifileshare)
Access: 2020-05-10 09:33:59.713840197 +0300
Modify: 2020-05-10 09:33:59.713840197 +0300
Change: 2020-05-10 09:33:59.714413772 +0300
Birth: -
[root@mn-0:/home/robot]
# cat /mnt/export/testfil
cat: /mnt/export/testfil: No such file or directory
[root@mn-0:/home/robot]
# cat /mnt/export/testfile
from mn0
from mn-1
fromm mn-0
[root@mn-0:/home/robot]
# date
Wed 11 Mar 2020 09:05:58 AM EET
[root@mn-0:/home/robot]
cynthia
From: Zhou, Cynthia (NSB - CN/Hangzhou)
Sent: 2020年3月11日 14:41
To: 'khiremat@xxxxxxxxxx' <khiremat@xxxxxxxxxx>
Subject: could you help to check about a glusterfs issue seems to be related to ctime
Hi glusterfs expert,
Good day!
Do you have a time to check the ticket : https://bugzilla.redhat.com/show_bug.cgi?id=1811907 ?
After I disable feature ctime this issue is gone, however, I meet erro “file changed as we read it” when using tar command.
Have you any idea?
Thanks!
Cynthia
Nokia storage team
--
Thanks and Regards,
Kotresh H R
--
Thanks and Regards,
Kotresh H R
--Thanks and Regards,Kotresh H R
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