From: rhomunuq+ml_sup@gmail.com (Iain)
Subject: [sup-talk] Lost Maildir Messages
Date: Wed, 15 Apr 2009 18:29:15 +0100 [thread overview]
Message-ID: <49E6196B.504@gmail.com> (raw)
In-Reply-To: <a412e2a70903191341o744efb9bw3a02ebb1585a9b8b@mail.gmail.com>
> Hm, that would be bad. The right way to debug this is to wait for it to
> happen again (!) and examine the contents of the poll-mode and log-mode
> buffers, which should describe what Sup thinks it was doing at the time.
I've noticed what seems to be the same problem.
I've been using getmail (no procmail or fetchmail), to grab messages
into Maildir folders. Occasionally, messages don't show up in Sup. They
appear only when I do a manual sup-sync --changed.
I discovered by accident (by impatiently trying to read an email that I
knew was being delivered by getmail into Sup) that I can reliably
replicate the problem, or at least a similar problem. It seems to occur
when Sup polls the Maildir at the same time as getmail is retrieving the
message.
I can replicate the problem by pressing P repeatedly in Sup to manually
poll for messages, while getmail is in the process of retrieving. (It
takes about 4 seconds for getmail to go from initialising a retrieval to
dropping the mail in the Maildir, so there is a big window for when I
press P, and I can replicate the problem reliably.) Every time, Sup
doesn't retrieve the new messages.
The log-mode buffer doesn't show anything relevant in my
artifically-produced replication of the problem, because it doesn't log
when you manually poll.
The poll-mode buffer for the source in question displays the exact same
message on every poll of the source (before getmail runs, during the
getmail run, after the getmail run) when repeatedly polling before and
during the getmail run:
Loading from maildir:///home/user/Mail/address at example.com/...
Found message at 12398138490002177 with labels {mylabel}
-- the timestamp never changes.
If I had to guess, I'd say that it looks like the shortcut taken
(looking at the mtime of the directory to see if scanning for a new
Maildir message is required) has a race condition. A weird race
condition, because I've verified (ls -l --time-style=+%s) that the "new"
and "tmp" folders are indeed having their timestamps updated when the
mail drops in (they are).
This might explain the infrequent lost messages: when not hitting P
repeatedly, this race condition is unlikely to occur, only happening
when the Sup poll occurs within the few seconds window during which
getmail is working and working with a new message to deliver.
~Iain
prev parent reply other threads:[~2009-04-15 17:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-16 17:27 [sup-talk] preparing for 0.7 William Morgan
2009-03-17 18:29 ` Mark Alexander
2009-03-18 13:49 ` William Morgan
2009-03-18 15:39 ` Lee Hinman
2009-03-19 17:02 ` William Morgan
2009-03-18 21:11 ` Mark Alexander
2009-03-19 19:18 ` Mark Alexander
2009-03-19 19:25 ` William Morgan
2009-03-19 20:41 ` Mark Alexander
2009-04-15 17:29 ` Iain [this message]
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