[Gluster-devel] Issue about the size of fstat is less than the really size of the syslog file
Lian, George (Nokia - CN/Hangzhou)
george.lian at nokia.com
Wed Nov 2 08:08:44 UTC 2016
Yes, I confirm use the Patch 2.
One update: the issue is occurred when readdir-ahead off and write-behind on.
Seems gone when write-behind and readdir-ahead and quick-read all off.
Not verified with readdir-ahead and quick-read both off and write-behind on till now.
Need I test it with write-behind on and readdir-ahead and quick-read both off?
Best Regards,
George
-----Original Message-----
From: Raghavendra Gowdappa [mailto:rgowdapp at redhat.com]
Sent: Wednesday, November 02, 2016 4:04 PM
To: Lian, George (Nokia - CN/Hangzhou) <george.lian at nokia.com>
Cc: Raghavendra G <raghavendra at gluster.com>; Gluster-devel at gluster.org; Zizka, Jan (Nokia - CZ/Prague) <jan.zizka at nokia.com>; Zhang, Bingxuan (Nokia - CN/Hangzhou) <bingxuan.zhang at nokia.com>
Subject: Re: [Gluster-devel] Issue about the size of fstat is less than the really size of the syslog file
----- Original Message -----
> From: "George Lian (Nokia - CN/Hangzhou)" <george.lian at nokia.com>
> To: "Raghavendra Gowdappa" <rgowdapp at redhat.com>
> Cc: "Raghavendra G" <raghavendra at gluster.com>, Gluster-devel at gluster.org, "Jan Zizka (Nokia - CZ/Prague)"
> <jan.zizka at nokia.com>, "Bingxuan Zhang (Nokia - CN/Hangzhou)" <bingxuan.zhang at nokia.com>
> Sent: Wednesday, November 2, 2016 1:29:13 PM
> Subject: RE: [Gluster-devel] Issue about the size of fstat is less than the really size of the syslog file
>
> Hi,
>
> When those 3 options turn off, the issue seems gone in about 3 hours,
> otherwise, the issue will be occurred about every 10 minutes.
That's a good news. IIRC, you mentioned that you saw the issue with just write-behind on, with fix applied (readdir-ahead and quick-read off). Can you please confirm you had patcset 2 of http://review.gluster.org/15757? patchset 1 had some issues that I corrected in 2.
>
> Best Regards,
> George
>
> -----Original Message-----
> From: Raghavendra Gowdappa [mailto:rgowdapp at redhat.com]
> Sent: Wednesday, November 02, 2016 1:07 PM
> To: Lian, George (Nokia - CN/Hangzhou) <george.lian at nokia.com>
> Cc: Raghavendra G <raghavendra at gluster.com>; Gluster-devel at gluster.org;
> Zizka, Jan (Nokia - CZ/Prague) <jan.zizka at nokia.com>; Zhang, Bingxuan (Nokia
> - CN/Hangzhou) <bingxuan.zhang at nokia.com>
> Subject: Re: [Gluster-devel] Issue about the size of fstat is less than the
> really size of the syslog file
>
> Can you try with following xlators turned off?
>
> 1. write-behind
> 2. readdir-ahead
> 3. quick-read
>
> regards,
> Raghavendra
>
> ----- Original Message -----
> > From: "George Lian (Nokia - CN/Hangzhou)" <george.lian at nokia.com>
> > To: "Raghavendra Gowdappa" <rgowdapp at redhat.com>, "Raghavendra G"
> > <raghavendra at gluster.com>
> > Cc: Gluster-devel at gluster.org, "Jan Zizka (Nokia - CZ/Prague)"
> > <jan.zizka at nokia.com>, "Bingxuan Zhang (Nokia -
> > CN/Hangzhou)" <bingxuan.zhang at nokia.com>
> > Sent: Wednesday, November 2, 2016 10:26:08 AM
> > Subject: RE: [Gluster-devel] Issue about the size of fstat is less than the
> > really size of the syslog file
> >
> > Hi,
> >
> > Sorry, it seems the issue still there with readdir-ahead off.
> >
> > # tail -f syslog >syslog.2.log
> > tail: syslog: file truncated
> > tail: syslog: file truncated
> > tail: syslog: file truncated
> > tail: syslog: file truncated
> > tail: syslog: file truncated
> >
> >
> >
> >
> >
> >
> >
> > tail: syslog: file truncated
> >
> > The last line is new truncated error message after the following set with
> > option readdir-ahead.
> >
> >
> > # gluster volume set log performance.readdir-ahead off
> > volume set: success
> > [root at SN-0(RNC-124) /root]
> > # gluster volume info log
> >
> > Volume Name: log
> > Type: Replicate
> > Volume ID: 9d987a23-1d64-4857-980a-548f1dd0d1e6
> > Status: Started
> > Number of Bricks: 1 x 2 = 2
> > Transport-type: tcp
> > Bricks:
> > Brick1: 169.254.0.12:/mnt/bricks/log/brick
> > Brick2: 169.254.0.13:/mnt/bricks/log/brick
> > Options Reconfigured:
> > performance.readdir-ahead: off
> >
> > BRs
> > George
> >
> > -----Original Message-----
> > From: gluster-devel-bounces at gluster.org
> > [mailto:gluster-devel-bounces at gluster.org] On Behalf Of Raghavendra
> > Gowdappa
> > Sent: Tuesday, November 01, 2016 9:29 PM
> > To: Raghavendra G <raghavendra at gluster.com>
> > Cc: Gluster-devel at gluster.org; Zizka, Jan (Nokia - CZ/Prague)
> > <jan.zizka at nokia.com>; Zhang, Bingxuan (Nokia - CN/Hangzhou)
> > <bingxuan.zhang at nokia.com>
> > Subject: Re: [Gluster-devel] Issue about the size of fstat is less than the
> > really size of the syslog file
> >
> >
> >
> > ----- Original Message -----
> > > From: "Raghavendra G" <raghavendra at gluster.com>
> > > To: "Pranith Kumar Karampuri" <pkarampu at redhat.com>
> > > Cc: Gluster-devel at gluster.org, "Jan Zizka (Nokia - CZ/Prague)"
> > > <jan.zizka at nokia.com>, "Bingxuan Zhang (Nokia -
> > > CN/Hangzhou)" <bingxuan.zhang at nokia.com>
> > > Sent: Tuesday, November 1, 2016 6:55:31 PM
> > > Subject: Re: [Gluster-devel] Issue about the size of fstat is less than
> > > the
> > > really size of the syslog file
> > >
> > > Hi George,
> > >
> > > You can try your tests in two scenarios:
> > >
> > > 1. Switch off following performance translators:
> > > a. write-behind
> > > b. quick-read
> > > c. readdir-ahead
> > >
> > > Once you see that the issue goes away in the above scenario, you can
> > > apply
> > > write-behind fix [1] and turn write-behind on.
> > >
> > > We have a fix in quick-read at [2].
> > >
> > > You can also try to test with the quick-read fix and turning quick-read
> > > on.
> > > However, since your issue is stale stat I doubt quick-read is not the
> >
> > s/quick-read is not the culprit/quick-read is the culprit/
> >
> > > culprit here (The issue with quick-read is stale data).
> > >
> > > We see that readdir-ahead is not updating/flushing the stats stored along
> > > with dentries when write or file modifications happen. That seem to be
> > > the
> > > issue with readdir-ahead. For now, during both of the above two
> > > scenarios,
> > > please keep readdir-ahead off.
> > >
> > > [1] http://review.gluster.org/15757/2
> > > [2] http://review.gluster.org/#/c/15759/2
> > >
> > > regards,
> > > Raghavendra
> > >
> > > On Tue, Nov 1, 2016 at 7:55 AM, Pranith Kumar Karampuri <
> > > pkarampu at redhat.com
> > > > wrote:
> > >
> > >
> > >
> > >
> > >
> > > On Tue, Nov 1, 2016 at 7:32 AM, Lian, George (Nokia - CN/Hangzhou) <
> > > george.lian at nokia.com > wrote:
> > >
> > >
> > >
> > >
> > >
> > > Hi,
> > >
> > >
> > >
> > > I will test it with your patches and update to you when I have result.
> > >
> > > hi George,
> > > Please use http://review.gluster.org/#/c/15757/2 i.e. second version of
> > > Raghavendra's patch. I tested it and it worked fine. We are still trying
> > > to
> > > figure out quick-read and readdir-ahead as I type this mail.
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Thanks a lots
> > >
> > >
> > >
> > > Best Regards,
> > >
> > > George
> > >
> > >
> > >
> > > From: Pranith Kumar Karampuri [mailto: pkarampu at redhat.com ]
> > > Sent: Monday, October 31, 2016 11:23 AM
> > > To: Lian, George (Nokia - CN/Hangzhou) < george.lian at nokia.com >
> > > Cc: Raghavendra Gowdappa < rgowdapp at redhat.com >; Zhang, Bingxuan (Nokia
> > > -
> > > CN/Hangzhou) < bingxuan.zhang at nokia.com >; Gluster-devel at gluster.org ;
> > > Zizka, Jan (Nokia - CZ/Prague) < jan.zizka at nokia.com >
> > >
> > > Subject: Re: [Gluster-devel] Issue about the size of fstat is less than
> > > the
> > > really size of the syslog file
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Removing I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX at internal.nsn.com , it is causing
> > > mail delivery problems for me.
> > >
> > >
> > > George,
> > >
> > >
> > > Raghavendra and I made some progress on this issue. We were in parallel
> > > working on another issue which is similar where elastic search indices
> > > are
> > > getting corrupted because of wrong stat sizes in our opinion. So I have
> > > been
> > > running different translator stacks in identifying the problematic
> > > xlators
> > > which are leading to indices corruption.
> > >
> > >
> > > We found the list to be 1) Write-behind, 2) Quick-read, 3) Readdir-ahead.
> > > Raghavendra and I just had a chat and we are suspecting that lack of
> > > lookup/readdirp implementation in write-behind could be the reason for
> > > this
> > > problem. Similar problems may exist in other two xlators too. But we are
> > > working on write-behind with priority.
> > >
> > >
> > > Our theory is this:
> > >
> > >
> > > If we do a 4KB write for example and it is cached in write-behind and we
> > > do
> > > a
> > > lookup on the file/do a readdirp on the directory with this file we send
> > > out
> > > wrong stat value to the kernel. There are different caches between kernel
> > > and gluster which may lead to fstat never coming till write-behind. So we
> > > need to make sure that we don't get into this situation.
> > >
> > >
> > > Action items:
> > >
> > >
> > > At the moment Raghavendra is working on a patch to implement
> > > lookup/readdirp
> > > in write-behind. I am going to test the same for elastic search. Will it
> > > be
> > > possible for you to test your application against the same patch and
> > > confirm
> > > that the patch fixes the problem?
> > >
> > >
> > >
> > >
> > >
> > > On Fri, Oct 28, 2016 at 12:08 PM, Pranith Kumar Karampuri <
> > > pkarampu at redhat.com > wrote:
> > >
> > >
> > >
> > >
> > > hi George,
> > >
> > >
> > > It would help if we can identify the bare minimum xlators which are
> > > contributing to the issue like Raghavendra was mentioning earlier. We
> > > were
> > > wondering if it is possible for you to help us in identifying the issue
> > > by
> > > running the workload on a modified setup? We can suggest testing out
> > > using
> > > custom volfiles so that we can slowly build the graph which could be
> > > causing
> > > this issue. We would like you guys to try out this problem with just
> > > posix-xlator and fuse and nothing else.
> > >
> > >
> > >
> > >
> > >
> > > On Thu, Oct 27, 2016 at 1:40 PM, Lian, George (Nokia - CN/Hangzhou) <
> > > george.lian at nokia.com > wrote:
> > >
> > >
> > >
> > > Hi, Raghavendra,
> > >
> > > Could you please give some suggestion for this issue? we try to find the
> > > clue
> > > for this issue for a long time, but it has no progress:(
> > >
> > > Thanks & Best Regards,
> > > George
> > >
> > > -----Original Message-----
> > > From: Lian, George (Nokia - CN/Hangzhou)
> > > Sent: Wednesday, October 19, 2016 4:40 PM
> > > To: 'Raghavendra Gowdappa' < rgowdapp at redhat.com >
> > > Cc: Gluster-devel at gluster.org ; I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX_GMS <
> > > I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX at internal.nsn.com >; Zhang, Bingxuan
> > > (Nokia
> > > -
> > > CN/Hangzhou) < bingxuan.zhang at nokia.com >; Zizka, Jan (Nokia - CZ/Prague)
> > > <
> > > jan.zizka at nokia.com >
> > > Subject: RE: [Gluster-devel] Issue about the size of fstat is less than
> > > the
> > > really size of the syslog file
> > >
> > > Hi, Raghavendra
> > >
> > > Just now, we test it with glusterfs log with debug-level "TRACE", and let
> > > some application trigger "glusterfs" produce large log, in that case,
> > > when
> > > we set write-behind and stat-prefetch both OFF,
> > > Tail the glusterfs log such like mnt-{VOLUME-NAME}.log, it still failed
> > > with
> > > "file truncated",
> > >
> > > So that means if file's IO in huge amount, the issue will still be there
> > > even
> > > write-behind and stat-prefetch both OFF.
> > >
> > > Best Regards,
> > > George
> > >
> > > -----Original Message-----
> > > From: Raghavendra Gowdappa [mailto: rgowdapp at redhat.com ]
> > >
> > >
> > > Sent: Wednesday, October 19, 2016 2:54 PM
> > > To: Lian, George (Nokia - CN/Hangzhou) < george.lian at nokia.com >
> > > Cc: Gluster-devel at gluster.org ; I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX_GMS <
> > > I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX at internal.nsn.com >; Zhang, Bingxuan
> > > (Nokia
> > > -
> > > CN/Hangzhou) < bingxuan.zhang at nokia.com >; Zizka, Jan (Nokia - CZ/Prague)
> > > <
> > > jan.zizka at nokia.com >
> > > Subject: Re: [Gluster-devel] Issue about the size of fstat is less than
> > > the
> > > really size of the syslog file
> > >
> > >
> > >
> > > ----- Original Message -----
> > > > From: "George Lian (Nokia - CN/Hangzhou)" < george.lian at nokia.com >
> > > > To: "Raghavendra Gowdappa" < rgowdapp at redhat.com >
> > > > Cc: Gluster-devel at gluster.org , "I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX_GMS"
> > > > < I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX at internal.nsn.com >, "Bingxuan Zhang
> > > > (Nokia - CN/Hangzhou)"
> > > > < bingxuan.zhang at nokia.com >, "Jan Zizka (Nokia - CZ/Prague)" <
> > > > jan.zizka at nokia.com >
> > > > Sent: Wednesday, October 19, 2016 12:05:01 PM
> > > > Subject: RE: [Gluster-devel] Issue about the size of fstat is less than
> > > > the
> > > > really size of the syslog file
> > > >
> > > > Hi, Raghavendra,
> > > >
> > > > Thanks a lots for your quickly update!
> > > > In my case, there are so many process(write) is writing to the syslog
> > > > file,
> > > > it do involve the writer is in the same host and writing in same mount
> > > > point
> > > > while the tail(reader) is reading it.
> > > >
> > > > The bug I just guess is:
> > > > When a writer write the data with write-behind, it call the call-back
> > > > function " mdc_writev_cbk" and called "mdc_inode_iatt_set_validate" to
> > > > validate the "iatt" data, but with the code I mentioned last mail, it
> > > > do
> > > > nothing.
> > >
> > > mdc_inode_iatt_set_validate has following code
> > >
> > > <snippet>
> > > if (!iatt || !iatt->ia_ctime) {
> > > mdc->ia_time = 0;
> > > goto unlock;
> > > }
> > > </snippet>
> > >
> > > Which means a NULL iatt sets mdc->ia_time to 0. This results in
> > > subsequent
> > > lookup/stat calls to be NOT served from md-cache. Instead, the stat is
> > > served from backend bricks. So, I don't see an issue here.
> > >
> > > However, one case where a NULL iatt is different from a valid iatt (which
> > > differs from the value stored in md-cache) is that the latter results in
> > > a
> > > call to inode_invalidate. This invalidation propagates to kernel and all
> > > dentry and page cache corresponding to file is purged. So, I am
> > > suspecting
> > > whether the stale stat you saw was served from kernel cache (not from
> > > glusterfs). If this is the case, having mount options
> > > "attribute-timeout=0"
> > > and "entry-timeout=0" should've helped.
> > >
> > > I am still at loss to point out the RCA for this issue.
> > >
> > >
> > > > And in same time, the reader(tail) read the "iatt" data, but in case of
> > > > the
> > > > cache-time is not timeout, it will return the "iatt" data without the
> > > > last
> > > > change.
> > > >
> > > > Do your think it is a possible bug?
> > > >
> > > > Thanks & Best Regards,
> > > > George
> > > >
> > > > -----Original Message-----
> > > > From: Raghavendra Gowdappa [mailto: rgowdapp at redhat.com ]
> > > > Sent: Wednesday, October 19, 2016 2:06 PM
> > > > To: Lian, George (Nokia - CN/Hangzhou) < george.lian at nokia.com >
> > > > Cc: Gluster-devel at gluster.org ; I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX_GMS
> > > > < I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX at internal.nsn.com >; Zhang, Bingxuan
> > > > (Nokia -
> > > > CN/Hangzhou) < bingxuan.zhang at nokia.com >; Zizka, Jan (Nokia -
> > > > CZ/Prague)
> > > > < jan.zizka at nokia.com >
> > > > Subject: Re: [Gluster-devel] Issue about the size of fstat is less than
> > > > the
> > > > really size of the syslog file
> > > >
> > > >
> > > >
> > > > ----- Original Message -----
> > > > > From: "George Lian (Nokia - CN/Hangzhou)" < george.lian at nokia.com >
> > > > > To: "Raghavendra Gowdappa" < rgowdapp at redhat.com >
> > > > > Cc: Gluster-devel at gluster.org , "I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX_GMS"
> > > > > < I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX at internal.nsn.com >, "Bingxuan Zhang
> > > > > (Nokia
> > > > > - CN/Hangzhou)"
> > > > > < bingxuan.zhang at nokia.com >, "Jan Zizka (Nokia - CZ/Prague)"
> > > > > < jan.zizka at nokia.com >
> > > > > Sent: Wednesday, October 19, 2016 10:51:24 AM
> > > > > Subject: RE: [Gluster-devel] Issue about the size of fstat is less
> > > > > than
> > > > > the
> > > > > really size of the syslog file
> > > > >
> > > > > Hi, Raghavendra,
> > > > >
> > > > > When we disable md-cache(gluster volume set log
> > > > > performance.md-cache-timeout
> > > > > 0), the issue seems gone.
> > > > > (we can't disable with " gluster volume set log performance.md-cache
> > > > > off"
> > > > > why?)
> > > >
> > > > Please use
> > > > #gluster volume set log performance.stat-prefetch off
> > > >
> > > > >
> > > > > So I double confuse that the code I abstract in last mail maybe have
> > > > > some
> > > > > issue for this case.
> > > > > Could you please share your comments?
> > > >
> > > > Please find my comments below.
> > > >
> > > > >
> > > > > Thanks & Best Regards,
> > > > > George
> > > > >
> > > > > -----Original Message-----
> > > > > From: Lian, George (Nokia - CN/Hangzhou)
> > > > > Sent: Friday, October 14, 2016 1:44 PM
> > > > > To: 'Raghavendra Gowdappa' < rgowdapp at redhat.com >
> > > > > Cc: Gluster-devel at gluster.org ; I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX_GMS
> > > > > < I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX at internal.nsn.com >; Zhang, Bingxuan
> > > > > (Nokia
> > > > > -
> > > > > CN/Hangzhou) < bingxuan.zhang at nokia.com >; Zizka, Jan (Nokia -
> > > > > CZ/Prague)
> > > > > < jan.zizka at nokia.com >
> > > > > Subject: RE: [Gluster-devel] Issue about the size of fstat is less
> > > > > than
> > > > > the
> > > > > really size of the syslog file
> > > > >
> > > > > Hi, Raghavendra,
> > > > >
> > > > > Our version of GlusterFS is 3.6.9, and I also check the newest code
> > > > > of
> > > > > main
> > > > > branch, the function of " mdc_inode_iatt_set_validate" is almost
> > > > > same,
> > > > > from
> > > > > the following code of this function,
> > > > > We could see a "TODO" comments inline, does it mean if we enhance
> > > > > write-behind feature, the "iatt" field in callback will be NULL, so
> > > > > that
> > > > > inode_invalidate will not be called? So the size of file will not
> > > > > update
> > > > > since "write behind" enabled ?
> > > > > Is it the root cause for "tail" application failed with "file
> > > > > truncated"
> > > > > issue ?
> > > > >
> > > > > LOCK (&mdc->lock);
> > > > > {
> > > > > if (!iatt || !iatt->ia_ctime) {
> > > > > mdc->ia_time = 0;
> > > > > goto unlock;
> > > > > }
> > > > >
> > > > > /*
> > > > > * Invalidate the inode if the mtime or ctime has changed
> > > > > * and the prebuf doesn't match the value we have cached.
> > > > > * TODO: writev returns with a NULL iatt due to
> > > > > * performance/write-behind, causing invalidation on writes.
> > > > > */
> > > >
> > > > The issue explained in this comment is hit only when writes are done.
> > > > But,
> > > > in
> > > > your use-case only "tail" is the application running on the mount (If I
> > > > am
> > > > not wrong, the writer is running on a different mountpoint). So, I
> > > > doubt
> > > > you are hitting this issue. But, you are saying that the issue goes
> > > > away
> > > > when write-behind/md-cache is turned off pointing to some interaction
> > > > between md-cache and write-behind causing the issue. I need more time
> > > > to
> > > > look into this issue. Can you file a bug on this?
> > > >
> > > > > if (IA_ISREG(inode->ia_type) &&
> > > > > ((iatt->ia_mtime != mdc->md_mtime) ||
> > > > > (iatt->ia_ctime != mdc->md_ctime)))
> > > > > if (!prebuf || (prebuf->ia_ctime != mdc->md_ctime) ||
> > > > > (prebuf->ia_mtime != mdc->md_mtime))
> > > > > inode_invalidate(inode);
> > > > >
> > > > > mdc_from_iatt (mdc, iatt);
> > > > >
> > > > > time (&mdc->ia_time);
> > > > > }
> > > > >
> > > > > Best Regards,
> > > > > George
> > > > > -----Original Message-----
> > > > > From: Raghavendra Gowdappa [mailto: rgowdapp at redhat.com ]
> > > > > Sent: Thursday, October 13, 2016 8:58 PM
> > > > > To: Lian, George (Nokia - CN/Hangzhou) < george.lian at nokia.com >
> > > > > Cc: Gluster-devel at gluster.org ; I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX_GMS
> > > > > < I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX at internal.nsn.com >; Zhang, Bingxuan
> > > > > (Nokia
> > > > > -
> > > > > CN/Hangzhou) < bingxuan.zhang at nokia.com >; Zizka, Jan (Nokia -
> > > > > CZ/Prague)
> > > > > < jan.zizka at nokia.com >
> > > > > Subject: Re: [Gluster-devel] Issue about the size of fstat is less
> > > > > than
> > > > > the
> > > > > really size of the syslog file
> > > > >
> > > > >
> > > > >
> > > > > ----- Original Message -----
> > > > > > From: "George Lian (Nokia - CN/Hangzhou)" < george.lian at nokia.com >
> > > > > > To: Gluster-devel at gluster.org
> > > > > > Cc: "I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX_GMS"
> > > > > > < I_EXT_MBB_WCDMA_SWD3_DA1_MATRIX at internal.nsn.com >, "Bingxuan
> > > > > > Zhang
> > > > > > (Nokia
> > > > > > - CN/Hangzhou)" < bingxuan.zhang at nokia.com >, "Jan Zizka (Nokia -
> > > > > > CZ/Prague)"
> > > > > > < jan.zizka at nokia.com >
> > > > > > Sent: Thursday, October 13, 2016 2:33:53 PM
> > > > > > Subject: [Gluster-devel] Issue about the size of fstat is less than
> > > > > > the
> > > > > > really size of the syslog file
> > > > > >
> > > > > > Hi, Dear Expert,
> > > > > > We have use glusterfs as a network filesystem, and syslog store in
> > > > > > there,
> > > > > > some clients on different host may write the syslog file via
> > > > > > “glusterfs”
> > > > > > mount point.
> > > > > > Now we encounter an issue when we “tail” the syslog file, it will
> > > > > > occasional
> > > > > > failed with error “ file truncated ”
> > > > > > As we study and trace with the “tail” source code, it failed with
> > > > > > the
> > > > > > following code:
> > > > > > if ( S_ISREG (mode) && stats.st_size < f[i].size )
> > > > > > {
> > > > > > error (0, 0, _("%s: file truncated"), quotef (name));
> > > > > > /* Assume the file was truncated to 0,
> > > > > > and therefore output all "new" data. */
> > > > > > xlseek (fd, 0, SEEK_SET, name);
> > > > > > f[i].size = 0;
> > > > > > }
> > > > > > When stats.st_size < f[i].size, what mean the size report by fstat
> > > > > > is
> > > > > > less
> > > > > > than “tail” had read, it lead to “file truncated”, we also use
> > > > > > “strace”
> > > > > > tools to trace the tail application, the related tail strace log as
> > > > > > the
> > > > > > below:
> > > > > > nanosleep({1, 0}, NULL) = 0
> > > > > > fstat(3, {st_mode=S_IFREG|0644, st_size=192543105, ...}) = 0
> > > > > > nanosleep({1, 0}, NULL) = 0
> > > > > > fstat(3, {st_mode=S_IFREG|0644, st_size=192543105, ...}) = 0
> > > > > > nanosleep({1, 0}, NULL) = 0
> > > > > > fstat(3, {st_mode=S_IFREG|0644, st_size=192543105, ...}) = 0
> > > > > > nanosleep({1, 0}, NULL) = 0
> > > > > > fstat(3, {st_mode=S_IFREG|0644, st_size=192544549, ...}) = 0
> > > > > > read(3, " Data … -"..., 8192) = 1444
> > > > > > read(3, " Data.. "..., 8192) = 720
> > > > > > read(3, "", 8192) = 0
> > > > > > fstat(3, {st_mode=S_IFREG|0644, st_size=192544789, ...}) = 0
> > > > > > write(1, “DATA…..” ) = 2164
> > > > > > write(2, "tail: ", 6tail: ) = 6
> > > > > > write(2, "/mnt/log/master/syslog: file tru"...,
> > > > > > 38/mnt/log/master/syslog:
> > > > > > file truncated) = 38
> > > > > > as the above strace log, tail has read 1444+720=2164 bytes,
> > > > > > but fstat tell “tail” 192544789 – 192543105 = 1664 which less than
> > > > > > 2164,
> > > > > > so
> > > > > > it lead to “tail” application “file truncated”.
> > > > > > And if we turn off “write-behind” feature, the issue will not be
> > > > > > reproduced
> > > > > > any more.
> > > > >
> > > > > That seems strange. There are no writes happening on the fd/inode
> > > > > through
> > > > > which tail is reading/stating from. So, it seems strange that
> > > > > write-behind
> > > > > is involved here. I suspect whether any of
> > > > > md-cache/read-ahead/io-cache
> > > > > is
> > > > > causing the issue. Can you,
> > > > >
> > > > > 1. Turn off md-cache, read-ahead, io-cache xlators
> > > > > 2. mount glusterfs with --attribute-timeout=0
> > > > > 3. set write-behind on
> > > > >
> > > > > and rerun the tests? If you don't hit the issue, you can experiment
> > > > > by
> > > > > turning on/off of md-cache, read-ahead and io-cache translators and
> > > > > see
> > > > > what
> > > > > are the minimal number of xlators that need to be turned off to not
> > > > > hit
> > > > > the
> > > > > issue (with write-behind on)?
> > > > >
> > > > > regards,
> > > > > Raghavendra
> > > > >
> > > > > > So we think it may be related to cache consistence issue due to
> > > > > > performance
> > > > > > consider, but we still have concern that:
> > > > > > The syslog file is used only with “Append” mode, so the size of
> > > > > > file
> > > > > > shouldn’t be reduced, when a client read the file, why “fstat”
> > > > > > can’t
> > > > > > return
> > > > > > the really size match to the cache?
> > > > > > From current investigation, we doubt that the current implement of
> > > > > > “glusterfs” has a bug on “fstat” when cache is on.
> > > > > > Your comments is our highly appreciated!
> > > > > > Thanks & Best Regards
> > > > > > George
> > > > > >
> > > > > > _______________________________________________
> > > > > > Gluster-devel mailing list
> > > > > > Gluster-devel at gluster.org
> > > > > > http://www.gluster.org/mailman/listinfo/gluster-devel
> > > > >
> > > >
> > > _______________________________________________
> > > Gluster-devel mailing list
> > > Gluster-devel at gluster.org
> > > http://www.gluster.org/mailman/listinfo/gluster-devel
> > >
> > >
> > >
> > >
> > >
> > >
> > > --
> > >
> > >
> > > Pranith
> > >
> > >
> > >
> > >
> > >
> > > --
> > >
> > >
> > > Pranith
> > >
> > >
> > >
> > > --
> > > Pranith
> > >
> > > _______________________________________________
> > > Gluster-devel mailing list
> > > Gluster-devel at gluster.org
> > > http://www.gluster.org/mailman/listinfo/gluster-devel
> > >
> > >
> > >
> > > --
> > > Raghavendra G
> > >
> > > _______________________________________________
> > > Gluster-devel mailing list
> > > Gluster-devel at gluster.org
> > > http://www.gluster.org/mailman/listinfo/gluster-devel
> > _______________________________________________
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> > Gluster-devel at gluster.org
> > http://www.gluster.org/mailman/listinfo/gluster-devel
> >
>
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