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<p style="margin-top:0;margin-bottom:0">Thank you for the feedback, Tony. I think a better understanding of what's going on under the hood will prove useful in both designing my operational management strategy as well as just talking me down off the ledge.
:) Much obliged. :)</p>
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<p style="margin-top:0;margin-bottom:0">Scott<br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> Tony Finch <dot@dotat.at><br>
<b>Sent:</b> February 26, 2020 10:05 AM<br>
<b>To:</b> Scott A. Wozny <sawozny@hotmail.com><br>
<b>Cc:</b> bind-users@lists.isc.org <bind-users@lists.isc.org><br>
<b>Subject:</b> Re: NS failover as opposed to A record failover</font>
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<div class="PlainText">Scott A. Wozny <sawozny@hotmail.com> wrote:<br>
><br>
> Failures aside, I’m worried about creating a bad user experience EVERY<br>
> time I need to take a DNS server down for patching.<br>
<br>
I generally let resolvers handle retry/failover when I'm patching my<br>
authoritative servers. Each resolver that encounters an authoritative<br>
server that is down will retry on another server within a few seconds, and<br>
should send follow-up queries to more responsive auth servers. There are<br>
several retries within the libc resolver timeout, so there are multiple<br>
opportunities to automatically deal with an outage within a reasonable<br>
amount of time. So the badness isn't that terrible. (i.e. less than the<br>
load time for a web page with megabytes of JavaScript.)<br>
<br>
I reckon this should be good enough for you, because it's a similar amount<br>
of badness that your users will encounter from your DNS UPDATE web server<br>
failover setup.<br>
<br>
If you want something better, on my recursive servers I use keepalived to<br>
move the service IP addresses off servers while they are being patched.<br>
You can do something similar for auth servers, if you have a little<br>
cluster in each location. On your web servers, keepalived and HAproxy is<br>
supposed to be a good combination (though I have not tried it myself).<br>
For servers that are too far apart for layer 2 failover to work, you'll<br>
need to get funky with anycast.<br>
<br>
Tony.<br>
-- <br>
f.anthony.n.finch <dot@dotat.at> <a href="http://dotat.at/" id="LPlnk296358" class="OWAAutoLink" previewremoved="true">
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<br>
German Bight: Northwest backing southwest later 4 to 6. Slight or moderate.<br>
Showers. Good, occasionally moderate.</div>
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