[Gluster-users] concurrent write and read to the same file

Lana Deere lana.deere at gmail.com
Mon Nov 1 15:58:16 UTC 2010

Thanks for the pointer, James.

In some ways the symptom seems different, since I was seeing correct
output on other nodes, but not on the node where it was being
generated, but otherwise it might well be a match.  I may try turning
quickread off on my volumes to see if it helps.

.. Lana (lana.deere at gmail.com)

On Mon, Nov 1, 2010 at 10:31 AM, Burnash, James <jburnash at knight.com> wrote:
> Hi Lana.
> Looks like you may have run into this bug as well:
> http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=2027
> James Burnash, Unix Engineering
> -----Original Message-----
> From: gluster-users-bounces at gluster.org [mailto:gluster-users-bounces at gluster.org] On Behalf Of Lana Deere
> Sent: Friday, October 29, 2010 5:06 PM
> To: gluster-users at gluster.org
> Subject: [Gluster-users] concurrent write and read to the same file
> GlusterFS 3.1.0, distributed volumes, rdma transport, CentOS 5.4/5.5.
> I was doing "tail -f" on a log file while the program generating it
> was running and noticed some strange behavior.  I wasn't able to
> reproduce exactly the same strange behavior, but here is some which
> did reproduce for me reliably.  This is a small perl program producing
> a bit of output every few seconds:
>    $| = 1;
>    for ($i=0; $i < 100; ++$i) {
>        printf("This is line $i\n");
>        sleep(3);
>    }
> If I run it with output sent to a gluster volume,
>   perl foo.pl > bar
> it works fine: "bar" has the right content after the script
> terminates, or if I kill the script while it runs "bar" has a valid
> partial output.
> While the perl script is running, if I log into a different host which
> can see that volume and do "tail -f bar" that also works fine: every
> few seconds, the next line of output appears.
> However, while the perl script is running if I do "tail -f bar" from
> the same host as the script is running on, it will print me the
> current end of the file but then it will hang without producing any
> subsequent output.  This is true whether or not I have a tail running
> on a different host concurrently.
> The tail on the same host as the script will correctly notice that the
> file was reset if I kill and restart the perl script while leaving the
> tail running.  Then it prints the first line, but at that point it
> hangs again.
> Anyone else seeing this?  Any ideas what might be reasons why?
> Thanks!
> .. Lana (lana.deere at gmail.com)
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