[ale] /etc/hosts and caching

[Tim Watts]

I can't say whether there's any caching on the kernel level but I do
know that some apps and libraries can do some caching.  This may explain
the contradictory experiences people have had.  Java has properties you
can set for this but I don't recall whether this overrides DNS or is
used as a default in lieu of other advice (i.e. /etc/hosts).


On Fri, 2011-11-04 at 07:40 -0400, Chesser.Damon wrote:
> This dovetails into building a DNS caching server I asked earlier this
> week.  The issue is we are seeing latency in our application and a
> possible (but only possible, not proven) issue might be host lookups.
> I figured that an entry into /etc/hosts would be faster than a WAN DNS
> lookup especially since the IP is static.  Someone was concerned with
> disk reads and that becoming a bottleneck.  Someone else pointed out
> that /etc/hosts file was cached.  
> 
>  
> 
> This started a google search by me to find out if that was true or
> not.  Totally inconclusive.  Some have reported issues with not being
> able to get the Linux box to re-read the hosts file after a change was
> committed short of a reboot or init restart.  Others have said just
> make the change and it shows up.  I have not found any documentation
> saying whether it was cached or not.  Any smart guys know the answer
> or can provide any documentation on that?  It’s kind of funny, you
> think you KNOW something until someone says “Prove it”.
> 
>  
> 
> Damon at damtek.com
> 
>  
> 
> 
>  
>  
>  
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