[HEADS UP] upcoming /etc/services updating

[Robert Watson]

On Sat, 29 Apr 2006, Ceri Davies wrote:

>> I think, that "perform-actual-lookups" mode should also be enabled for 
>> "services" by default in cached.conf - so that the cache for services 
>> information would be the same for all users.
>
> So "perform-actual-lookups" essentially creates a system-wide cache?
>
>>  Besides, as services information changes extremely rarely, I'd also 
>> suggest putting greater TTL values for "services" in the cached.conf.
>
> Yes, the services cache could always be flushed by the superuser after 
> changing the services data source.

Very few sites use distributed services databases (at least, that I've ever 
seen).  Performing stat() on /etc/services to check the last modification date 
is pretty light-weight, and probably worth doing.  What you don't want is 
someone modifying /etc/services, restarting the daemon immediately, and having 
it fail due to an added service not being found.  Likewise for other local 
databases.

BTW, since this is in the context of significantly increasing the size of the 
services database, have we:

(1) Measured what impact adding the cache daemon for local databases has?
     Specifically, does adding the cache daemon for a database like
     /etc/services, /etc/passwd, etc, improve performance, or add overhead?

(2) Looked at adding /etc/services.db, similar to the other compiled database
     pieces, in order to improve lookup times for very large tables.  This
     change would be orthoganal to a cache daemon.

Robert N M Watson