[syslog-ng] DNS Cache with /etc/hosts
bazsi at balabit.hu
Fri May 16 12:52:37 CEST 2008
On Thu, 2008-05-15 at 09:27 +0100, Hari Sekhon wrote:
> Andrew Kerr wrote:
> > I have the following set:
> > use_dns(persist_only);
> > dns_cache(yes);
> > dns_cache_hosts(/etc/hosts);
> > After I make a change to /etc/hosts, how long until syslog-ng will pick up
> > the change?
> > ______________________________________________________________________________
> > Member info: https://lists.balabit.hu/mailman/listinfo/syslog-ng
> > Documentation: http://www.balabit.com/support/documentation/?product=syslog-ng
> > FAQ: http://www.campin.net/syslog-ng/faq.html
> From the administrator's manual:
> dns_cache_expire() number 3600 Number of seconds while a successful
> lookup is cached.
> so you will either have to wait that many seconds (3600) by default or
> it will be instantaneous, depending on the behaviour of syslog-ng.
> So the question now becomes
> Does the /etc/hosts file bypass the cache the same way that the os does
> and make the change instantaneous?
any change to the /etc/hosts file triggers a reload into syslog-ng's
cache. so yes, it is instantanous.
> On linux for example any change made to the /etc/hosts file results in
> instant redirection to the new lookup result even when a name cache
> daemon is running, I would expect syslog-ng to do the same in some ways,
> although I wouldn't be surprised if it didn't for performance reasons...
> The line below from the administrator's manual implies that it would be
> instantaneous since if it bypasses dns then surely it doesn't use the
> "Name of a file in |/etc/hosts| format that contains static IP->hostname
> mappings. Use this option to resolve hostnames locally without using a DNS."
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