[Dnsmasq-discuss] Polling of hosts file
simon at thekelleys.org.uk
Thu Mar 20 15:39:01 UTC 2014
On 19/03/14 09:24, Franco Broi wrote:
> I hear what you say but for me it would be very convenient, I have
> several dnsmasq servers all reading the same shared hosts file.
> My currently solution is to run a script from cron that detects a change
> and sends HUP to dnsmasq.
That sounds like a good solution, especially if you arrange to replace
the file atomically, ie write hosts.new, then mv hosts.new to hosts
> You could have a few simple safeguards, like delaying the update if the
> number of hosts has reduced drastically etc..
You could, and they would have the effect of turning frequent failures
into infrequent and difficult to diagnose failures.
> On Wed, 2014-03-19 at 09:07 +0000, Simon Kelley wrote:
>> On 19/03/14 04:04, Franco Broi wrote:
>>> Just wondering why dnsmasq doesn't poll the hosts file for changes like
>>> it does for resolv.conf?
>> Polling files is dangerous. You can get race conditions where the update
>> time changes but the file is still in the process of being written.
>> Polling resolv.conf is necessary because there are lots of things which
>> just write it and expect the changes to be picked up (because that's
>> what the resolver library does.) That's not true for /etc/hosts, so it's
>> better to mandate the update-then-signal model.
>> Dnsmasq-discuss mailing list
>> Dnsmasq-discuss at lists.thekelleys.org.uk
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