[Gluster-users] tailing active files

[Keith Freedman]

this is interesting.

I'm running glusterfs--mainline--3.0--patch-840

using AFR.
I did your test
on the local machine, running tail does exactly what you indicated... 
it acts like it was run without the -f.
on the other replication server, lines show up 2 at a time.
so it started at 9 or something
then I got 10 & 11, 2 seconds later, 12, 13, etc...
the same time tail -f on the server I was running the thing on sat 
there a while then produced some output.

again, the afr machine updated more frequently, but the local machine 
just needed to get past some buffering

what I saw was (you'll notice this faster if you remove the sleep)
it would show some numbers, then jump and show another batch of 
numbers, then pause then show another batch.
here's an output from tail -f
Notice that at 63, there was some weirdness, like it was trying to 
print 1041 and 1860, I'm guessing
then I got 1861 -.... and then I'd get a jump in numbers.. if I cat 
the file all the numbers are there.

Also, in some of my tests I got input/output errors ----  I belive 
this was due to having tail -f running on the other afr server and 
this code you provided using > which truncates the file.  seems AFR 
has a little bug there if a file is open for reading on the other 
server and is truncated.  the io error went away when I killed the 
tail process on the other machine.

55
56
57
58
59
60
61
62
63
041
60
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872

I also noticed


At 02:25 PM 1/12/2009, Bryan Talbot wrote:
>I'm running 1.4rc7 (glusterfs--mainline--3.0--patch-814) and seeing 
>some odd behavior when tailing a file that is being written to by a 
>single process --  a log file in this case.
>
>The odd behaviors that I've noticed are that "tail -f" behaves like 
>"tail" and doesn't show any updates.  In addition, /usr/bin/less 
>seems to show binary values (at least that's what I assume the "^@" 
>characters are supposed to be) when the bottom of the file "G" 
>accessed instead of the new data added to the file after less was started.
>
>Is this a known issue?  Is there a work-around?
>
>Here's how I'm able to reproduce it.  Run the script below and 
>direct the output to a gluster-hosted file.  Then attempt to "tail 
>-f" or use /usr/bin/less on the file from another terminal.
>
>
>$> num=0; while [ 1 ]; do echo $((num++)); sleep 1; done > 
>/mnt/gluster/nums.txt
>
>
>The output from /usr/bin/less ends up looking like this:
>...
>301
>302
>303
>304
>305
>306
>307
>308
>309
>310
>311
>^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
>
>
>Gluster configs are very basic:
>## Server
>volume brick
>  type storage/posix
>  option directory /glusterfs/export
>end-volume
>
>volume lock
>   type features/posix-locks
>   subvolumes brick
>end-volume
>
>volume export
>   type performance/io-threads
>   subvolumes lock
>   option thread-count 4 # default value is 1
>end-volume
>
>volume server
>  type protocol/server
>  option transport-type tcp
>  subvolumes export
>  option auth.addr.export.allow 10.10.10.*
>end-volume
>
>
>
>## Client
>volume volume1
>   type protocol/client
>   option transport-type tcp/client
>   option remote-host    10.10.10.2
>   option remote-subvolume export
>end-volume
>
>volume volume2
>   type protocol/client
>   option transport-type tcp/client
>   option remote-host    10.10.10.3
>   option remote-subvolume export
>end-volume
>
>volume mirror1
>   type cluster/afr
>   subvolumes volume1 volume2
>end-volume
>
>
>
>-Bryan
>
>
>
>
>_______________________________________________
>Gluster-users mailing list
>Gluster-users at gluster.org
>http://zresearch.com/cgi-bin/mailman/listinfo/gluster-users