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List:       netatalk-devel
Subject:    Re: [Netatalk-devel] CNID refactored.
From:       Rafal Lewczuk <rlewczuk () pronet ! pl>
Date:       2003-05-30 9:56:12
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Joerg wrote:
> Interesting. I have done some work in that area as well but using a
> different approach: I have put all of the database code into a
> separate daemon (one daemon per volume) and afpd contacts that daemon
> for everything related to CNIDs. That has the advantages mentioned
> above (it does not really matter what kind of database is used for a
> volume anymore), eliminates any locking or database consistency
> problems and makes transactions work properly. The problem with
> several afpd daemon accessing a database in transactional mode is that
> if one of them crashes or exits without properly releasing all
> database ressources, all other daemons should also exit immediately
> and recovery on the volume database must be run. A simple kill -9 by an
> administrator is therefore enough to potentially cause database
> corruption. The separate daemon instance solves that problem by
> running recovery automatically on startup.

Now it may be plugged as a new CNID backend. If it has similiar api to
original approach (eg. cnid_* functions reimplemented) porting should be
trivial.

> There is one drawback: Contacting a daemon causes IPC overhead, which
> the current scheme does not have, but I think that is dominated by
> disk access and database lookups. Some testing in a larger environment
> with many stations accessing the same volume should indicate if this
> is a problem. 

This may be minor drawback as CNID traffic is relatively low, compared 
to others. And local IPC is fast.

> If someone is interested in the patches, let me know.

Sure, I'm interested ;)

-- 
Rafal Lewczuk <rlewczuk@pronet.pl>
"Pronet" Nikołajuk Rozmus Muliński Spółka jawna



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