[Kroupware] [ot] maildir & locking (was: Re: Web interface frontend)

[konold@erfrakon.de]

On Fri, 27 Sep 2002, Marc Mutz wrote:

Hi MArc,

I will due to time pressure not go into the details.

> Yes? What can go wong?

Many things!

> Status updates are mv's, which are atomic on
> almost all OSs.

mv's are only atomic on mosts OSs on a single local filesystem. E.g. if
/tmp and your maildir repository live on different filesystems mv's are
not atomic anymore. Having /tmp on a separate fs is very common in larger
setups.

On the other hand nfs is by _definition_ not a POSIX compatible fs and is
normally for performance reasons used in asynchronous mode....

>  Adding a new mail is done via assembling it in tmp/,
> then mv'ing it to new/. Changing a mail's content is done by writing
> the new version to tmp/, then mv'ing it over the old one.
>
> Where do you see locking issues here?

Imagine that two clients access the same maildir repository on a nfs
server.

How do you guarantee that there is no naming collision if both are
simultaneously creating new messages?

Yours,
-- martin

Dipl.-Phys. Martin Konold

e r f r a k o n
Erlewein, Frank, Konold & Partner - Beratende Ingenieure und Physiker
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email: martin.konold@erfrakon.de