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List:       proftpd-users
Subject:    Re: [Proftpd-user]  =?utf-8?q?Exceptional_slowness_and_lost_connectio?=
From:       "TJ Saunders" <tj () castaglia ! org>
Date:       2019-12-18 22:34:39
Message-ID: 0f871b72-12ae-4852-8c8a-b9ca84354d80 () www ! fastmail ! com
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> We've been using 1.3.5e for a long time without issue. However when we
> attempted to shift to 1.3.6b many of our users are suddenly unable to
> complete their authentications and timing out, and those that can get
> that far encounter exceptionally long lags on doing simple 'dir/ls'
> commands, on the order of 2-4 minutes to get returns. These problems
> cease as soon as we fail back to 1.3.5e, so it is not something with
> our network or firewalls.
> 
> The configuration file used is the same one, it's not two different
> identical files, it is literally the same file. Other than sanitizing
> it for IP addresses and names (and pulling out comments) it is posted
> below.
...

One of the largest culprits for slower directory listings -- especially for "wider" \
(flat, with many thousands of files) directories, was only recently fixed, and I \
haven't had time to do releases with the fix yet:

  https://github.com/proftpd/proftpd/issues/863

Many FTP users use graphical FTP clients, which do a directory listing after \
authentication, thus such users often report "slow login", even though the issue may \
more accurately be "slow directory listing".

If you're able to test the latest 1.3.6 branch (or master), you might see if the \
slowness is gone for you.  Alternatively, in your 1.3.6b configuration, you might try \
using:

  FSCachePolicy off

which disables the caching of stat(2)/lstat(2) filesystem results -- whose \
inefficient implementation is causing the latency.  (The current code uses a much \
simpler and more efficient means of caching that same data, without the latency \
penalty.)

Hope this helps,
TJ


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