NSD doesn't refresh zones after extended downtime

[nlnetlabs]

NSD doesn't refresh zones after extended downtime

[wcawijngaards]

Hi Anand. Yes that is right, fixed it in commit 784600e where it fetches immediately, and then if that needs retries, the already existing logic for spreading retries can spread load. This is also how it works when NSD is started without files. So this fix makes all the zones get fetched immediately.

[wcawijngaards]

Hi Anand,
Thanks for the report! I added the logic so that when it reads in the xfrdfile it checks if the timeout is in the past. If so, it attempts to refetch the zone contents. Because that probably affects all of the zones in the file, it spreads the load over a couple of seconds with a random(10) second delay. That works in a test setup for me.
Best regards, Wouter

[aabdnn]

Hi Wouter! Thanks for the fix. Actually I was aware of this issue for ages, but kept forgetting to open a report. Today, when I built 4.2.1 for testing, and noticed it again, I decided to open the report before I forgot again. I will try to rebuild with this patch and report to you, or just test with 4.2.2 comes out.

[aabdnn]

Hi Wouter. I tried this today, and it works as you described. NSD starts, notices that the zones are way out of date, and schedules refresh for them with a random delay of up to 10 seconds. I guess this is fine, but in reality, there is probably no need for the delay, because it would be fine if NSD just immediately refreshes the zones. If you start NSD without any zone files or xfrd.state, then it XFRs all the slaves zones in immediately. It doesn't make too much sense to add a random 10s delay for this specific case of extended downtime. For consistency, if you're going to add a random delay, then it should be for all cases, to avoid flooding a master server.