This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: Speeding up nscd
Petr Baudis <pasky@ucw.cz> writes:
> nscd has a bad reputation due to a fairly long history of bugs;
Indeed, that's an understatement.
> this stems from ugly spaghetti code and very aggressive use of
> multi-threading coupled with some synchronization issues in sensitive
> areas like garbage collection.
Also, the original Solaris nscd and I believe early glibc verisons
completely ignored DNS TTLs. That was an absolute catastrophe.
Generally, it only took one time of trying to track down a name resolution
bug for two or three hours (with host and dig showing nothing wrong at
all) and finally figuring out that nscd was just lying to the rest of the
system. After that, the poor system administrator would vow to seek out
and destroy every copy of nscd running on any system so that could never
happen again. Its benefits are otherwise marginal on systems that don't
use NIS or LDAP nsswitch modules heavily.
Per Urlich at http://udrepper.livejournal.com/16362.html this bug has been
fixed in glibc since late 2004, but having had that debugging experience,
I have to say that it's... memorable. I suspect that many people just
haven't gotten the message that this was fixed long ago, and "disable nscd
or your DNS caching will be broken" has now entered the common lore and is
being copied from system to system by people who have only heard stories
about the original problems.
--
Russ Allbery (rra@stanford.edu) <http://www.eyrie.org/~eagle/>