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Re: BDB notes

On Thursday, April 24, 2003, at 03:58  AM, Howard Chu wrote:

-----Original Message-----
From: jimd@siu.edu [mailto:jimd@siu.edu]
Subject: Re: 2.1.17 performance issues


Howard - would you please add the question below, and your
execellent answer
to it, to the FAQ? This would help all of us greatly. Thank you.


I've added hyperlinked notes on configuring back-bdb here:
http://www.openldap.org/faq/index.cgi?file=893

Great! But shouldn't this text in (a) the Admin Guide and (b) the slapd-bdb(5) manpage? The FAQ is a navigational mess and the search is rather broken.

I've been following the rants about bdb problems and documentation. I've got some observations:

* It seems that bunches of folks are having problems with the bdb backend.

* It seems like most of these folks are having problems because of a missing external-to-slapd bdb configuration.

* Other folks cry out RTFM! Then clarify that TFM includes: all bundled READMEs, manual pages, admin guide and FAQ (with its navigational and search problem), and the SleepyCat documentation.

* The previous default backend, back-ldbm, was entirely configured and operated by slapd.conf and slapd. No non-OpenLDAP documentation, configuration files or tools required, or even particularly relevant.

* back-bdb is billed in assorted places in the TFM as being like back-ldbm but better, essentially an upgrade for back-ldbm.

* Many folks, myself included, assumed the "upgrade" version, back-bdb, to be essentially a direct replacement configured and managed just like back-ldbm. In the absence of any obvious clue to the contrary in TFM, we setup back-bdb like we setup back-ldbm.

* We then go to the list asking about performance problems and are tersely told to RTFM, but are still confused. Yes, we can read TFM. The problem is that there is nothing in TFM to clue us into our incorrect assumption about back-bdb being operationally the same as back-ldbm and I have not seen that detail it clearly articulated on the list either. This is a classic case of developers being too close to the software to appreciate what seemingly simple things trip up the rest of us who have vastly less intimate knowledge of how everything fits together. This is nothing to be ashamed of, it happens all the time which is why, in general, programmers should not write documentation.


The bottom line appears to be that if you think of back-bdb as a drop-in replacement for back-ldbm, you WILL have big problems. Since back-bdb is the default backend, this must be clearly documented in multiple obvious places or the above ugly chain of events will frequently reoccur.

If this great new FAQ entry, or some shortened proxy with a link to the full entry, is placed in the back-bdb manual page and the Admin Guide, I predict that the whole ugly chain of events documented above will be eliminated for a vast majority of sysadmins using OpenLDAP.

-john