Re: [Dnsmasq-discuss] Polling of hosts file
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. Cheers, Simon. > > On Wed, 2014-03-19 at 09:07 +, Simon Kelley wrote: >> On 19/03/14 04:04, Franco Broi wrote: >>> Hi >>> >>> 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. >> >> >> Cheers, >> >> Simon. >> >> >> ___ >> Dnsmasq-discuss mailing list >> Dnsmasq-discuss@lists.thekelleys.org.uk >> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss > > > ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
Re: [Dnsmasq-discuss] Polling of hosts file
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. You could have a few simple safeguards, like delaying the update if the number of hosts has reduced drastically etc.. On Wed, 2014-03-19 at 09:07 +, Simon Kelley wrote: > On 19/03/14 04:04, Franco Broi wrote: > > Hi > > > > 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. > > > Cheers, > > Simon. > > > ___ > Dnsmasq-discuss mailing list > Dnsmasq-discuss@lists.thekelleys.org.uk > http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
Re: [Dnsmasq-discuss] Polling of hosts file
On 19/03/14 04:04, Franco Broi wrote: > Hi > > 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. Cheers, Simon. ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
