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[Pan-users] Re: Weird cache problem
From: |
Jim Henderson |
Subject: |
[Pan-users] Re: Weird cache problem |
Date: |
Sat, 29 Aug 2009 03:54:04 +0000 (UTC) |
User-agent: |
Pan/0.132 (Waxed in Black) |
On Sat, 29 Aug 2009 03:31:16 +0000, Duncan wrote:
> I've seen absolutely nothing like that here, multiple servers, but not
> multiple authenticated ones (one authenticated, some time ago, none for
> awhile tho).
Good to know. I actually have a total of 4 servers plus one dummy
(0.0.0.0 - which I use for my default posting profile so I don't
accidentally post to a group with a bad profile - had that happen too
many times).
There is actually another weird piece to this that I had forgotten about,
and that's that occasionally when posting a reply, I'll get a "no such
group: <group.goes.here>" when posting a reply. The dumb thing is that
the group, while hosted on the server I'm posting to, isn't actually the
group I'm posting to; it's nowhere in my headers. So I might be posting
to, say, opensuse.org.help.install-boot-login and when I post, I get a
message saying "no such group: novell.community.chat". Now o.o.h.i is
hosted on the same server as n.c.c. Both groups are actually hosted on
both servers (forums.novell.com and forums.opensuse.com - they're
actually the same server with two different DNS addresses). I recently
became a moderator on forums.opensuse.org so I use a set of login
credentials to access some private groups. I also use a different set of
credentials on forums.novell.com.
And to really confuse things, I read the forums.opensuse.org groups using
the forums.novell.com address, but when I got the new credentials, I
switched servers (to make it easier to deal with the authentication).
Both of the groups above are public groups - accessible with or without
authentication.
Come to think, there is a third oddity that I just realized was new -
occasionally when hitting groups on forums.opensuse.org, a group's
headers will completely redownload, and old messages (that haven't
expired) will show up as unread.
> Two observations:
>
> One: I /have/ seen occasional problems with posts that show no bodies
> at all. From my troubleshooting, this almost always involves posts with
> some exotic non-ASCII character, say a UTF-8 no-wrap-blank-space (IDR
> for sure what the technical term for them is ATM, is that correct?, I
> just woke up and my mind is still coming back up to speed) or the like.
I see this from time to time, in two different forms. If I see that the
article is cached and I can't see anything, I toggle quoting - one state
it shows, one state it doesn't.
If it isn't cached (as occasionally happens when reading this list or
others through gmane), if I read a few messages (or I've found, just hit
"enter" repeatedly on the message), eventually it'll download and I'll
see it.
> But I don't see how that's directly connected to the behavior you're
> seeing. It just came to my mind as a similar oddity.
Yeah, this is something different - but it is a similar oddity.
> It is possible
> that it's that oddity triggering it, but with different results due to
> some other oddity, or if you're on 32-bit, maybe it's the same oddity
> expressed in 32-bit where mine is 64-bit (x86_64 aka amd64).
I'm actually on x86_64 here as well.
> Two: About how pan's cache works: Pan saves the actual messages using
> the message-ID as the filename, translating filesystem-invalid
> characters where necessary. It's thus possible to troubleshoot if you
> can figure out the message-ID (say from the attribution of a reply, or
> by grepping the cache for a file containing the subject, author, group,
> etc.
Hmmm, that's a good idea. I'll give that a try - I usually can see a
reply to the problem message (in fact, so far, I think I always have been
able to open other messages and read them without a problem).
> If you save the message text, pan uses the same message-id for saving
> that, possibly just copying the cache file to wherever you save the
> message, possibly copying the message as in pan's own memory buffer but
> using the same message-id as a filename. It could be worthwhile to try
> that with both the original "duplicated" message, and the
> fake-duplicate, when you see the problem, as an initial troubleshooting
> measure.
The weird thing is that if I restart the problem goes away for a while -
it's not reproducible with a specific message. But next time I see it
happen, I'll have a look at the cache directory.
> Meanwhile, it seems to me the problem must be that for some reason, pan
> isn't updating its message-ID pointer when you change messages, so you
> see the same one, instead of the new one. There must be some code path
> without that critical update, or perhaps more likely, with a race
> condition between two threads. (Most of pan is single-threaded, but
> worker threads are hatched in certain cases, generally where there was
> an observed bottleneck.)
The really odd thing is that this didn't ever happen until I changed that
authentication setting. There seems to be a correlation.
> Which brings up the question in regard to threading: How many
> connections do you have running to each of the servers concurrently, and
> how many CPU cores is your machine? For the programmers out there (I
> speak and understand the lingo and concepts to some degree, but don't
> claim to be a programmer), it should be clear where I'm going with this.
> Multiple threads, multiple cores processing them, very good recipe for
> thread-races if the code isn't 100% concurrent-multi-entrant.
2 core system, 4 connections per server.
With the total of three oddities now, I'm wondering if I ought to wipe
the config and start over and see if the problem persists. Maybe
something in my config is borked.
Jim
--
Jim Henderson
Please keep on-topic replies on the list so everyone benefits