atom feed24 messages in net.sourceforge.lists.courier-users[courier-users] Re: problem courier p...
FromSent OnAttachments
Jérôme BollietJan 8, 2003 4:19 am 
Roland SchneiderJan 8, 2003 6:05 am 
Jérôme BollietJan 9, 2003 3:51 am 
Xavier BeaudouinJan 9, 2003 4:28 am 
Roland SchneiderJan 9, 2003 5:09 am 
Sam VarshavchikJan 9, 2003 5:11 am 
Xavier BeaudouinJan 9, 2003 5:54 am 
Jérôme BollietJan 9, 2003 6:37 am 
Brian CandlerJan 9, 2003 7:00 am 
Jérôme BollietJan 9, 2003 7:46 am 
Brian CandlerJan 9, 2003 7:59 am 
Xavier BeaudouinJan 9, 2003 8:04 am 
bi...@mics.org.ukJan 9, 2003 8:15 am 
Jérôme BollietJan 9, 2003 8:43 am 
Matt PavlovichJan 9, 2003 8:56 am 
Brian CandlerJan 9, 2003 9:06 am 
Xavier BeaudouinJan 9, 2003 9:46 am 
Gordon MessmerJan 9, 2003 2:22 pm 
Gordon MessmerJan 9, 2003 2:23 pm 
Sam VarshavchikJan 9, 2003 2:56 pm 
Sam VarshavchikJan 9, 2003 2:56 pm 
Xavier BeaudouinJan 9, 2003 3:49 pm 
Xavier BeaudouinJan 9, 2003 4:03 pm 
Jérôme BollietJan 9, 2003 11:43 pm 
Subject:[courier-users] Re: problem courier pop3d & load average
From:bi...@mics.org.uk (bi@mics.org.uk)
Date:Jan 9, 2003 8:15:42 am
List:net.sourceforge.lists.courier-users

Jérôme Bolliet writes:

Brian Candler wrote:

On Thu, Jan 09, 2003 at 02:54:34PM +0100, Xavier Beaudouin wrote:

Le jeudi, 9 jan 2003, à 14:10 Europe/Paris, Sam Varshavchik a écrit :

[... snip ...]

solaris... With about > 600 000 users, so I may be don't know what I am talking about...

Look at the code for handling the cache file.

1. It opens and reads the courierpop3dsizelist file (if any)

2. For all files which are in the mailbox but not in the cache, it works out the size as before. For all files which are in the cache but not in the directory listing, they are forgotten about.

3. It then writes the updated cache to a temporary file and then does an atomic rename to 'courierpop3dsizelist'. At all instants the file is complete and valid. There is no need to lock the file. There is no race condition.

To move the temporary file, you need to delete the current courierpop3dsizelist before. In this case, what is happen if another pop3d process try to access between the delete and the move.

Well, let's see, shall we?

Quoting from above: 1. It opens and reads the courierpop3dsizelist file (if any)

So there is no collision, no problem, just a single mailbox scan, as the cache will be considered empty. So the question is how frequently this event will occur. How frequently do you really get multiple pop3d processes reading the same mailbox in your installation? Compare this with the time you save by not having to bother with file locks.

The file is never modified, only replaced in its entirety. That's what makes it safe.

Regards,

Brian.

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