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List:       kmail-devel
Subject:    Bug#45694: acknowledged by developer (kmail fails to update its folder index properly)
From:       Don Sanders <sanders () kde ! org>
Date:       2002-07-30 6:26:12
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On Tuesday 30 July 2002 08:07, Ingo Klöcker wrote:
> Today it's clear that it was a bad design decision to assume that
> KMail is the only program which accesses ~/Mail.

Ingo I strongly disagree.

File locking of ~/Mail is the bad idea and should be discouraged. 
There's no standard for the locking mechanism which is dangerous, and 
file locking doesn't prevent partially written mails from being 
written.

These flaws in ~/Mail  locking  are why Maildir was developed.

But my main problem with locking of ~/Mail is that it is a 
non-scalable design, it makes it impossible to index the mbox files 
efficiently. Under the ~/Mail locking design external programs can 
not only append to mbox files but modify them randomly, some programs 
do so without changing the file date. Thus the only way to handle 
mbox files under the ~/Mail locking design is to rescan them 
completely.

Scalable mail clients do no support ~/Mail locking. Evolution, Mozilla 
and KMail all keep index files and do not support ~/Mail locking.

KMail is able to efficiently handle much larger folders than clients 
that depend on ~/Mail locking like pine and mutt.

> This will be fixed
> at some time in the future.

Locking of mbox files in ~/Mail is a fundamentally flawed designed. It 
can't be fixed and still allow for efficient handling of large 
folders.

KMail can be criticised for keeping mail in ~/Mail and not supporting 
file locking since locking of files in ~/Mail used to be something of 
a standard. But this criticism is weak as before KMail used ~/KMail 
and many users complained asking the KMail developers to use ~/Mail 
instead.

Really the problem is with users who mistakenly assume KMail supports 
a broken design like ~/Mail locking. Unfortunately such an assumption 
might be stupid but it is also human and common. Instead of checking 
for reliance on ~/Mail locking (that is checking to see if an 
external program modifies mbox files in ~/Mail) and silently trying 
to work around this, it would be much better if KMail checked and 
gave a strong visual warning to users that ~/Mail locking is not 
supported.

Unfortunately we can't do this without upsetting NFS users. Because 
NFS is broken by design and triggers our checks for external programs 
modifying mbox files.

I think the best thing is to check for mbox files being modifed by 
external programs, and show a warning. This warning should indicate 
how to turn of mbox checking for NFS users.

Don Sanders


(Complete bug history is available at http://bugs.kde.org/db/45/45694.html)
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