On 2018-04-06 02:47 AM, W.C.A. Wijngaards via Unbound-users wrote:
Hi Marc,

On 04/04/18 20:29, Marc Branchaud via Unbound-users wrote:
Hi all,

I have a simple forward-everything setup with serve-expired enabled:

         serve-expired: yes
         name: .
         forward-addr: X.X.X.X

If I use "flush_zone ." to clear the cache, I still get cache hits for
supposedly-absent entries (dump_cache shows that the cache is empty).

When I turn serve-expired off, "flush_zone ." results in cache misses
for flushed entries.

With serve-expired on, I can only seem to force a cache miss by
explicitly flushing a name (e.g. "flush google.com").  I really want to
clear the entire cache, though.

Is this an intended effect of serve-expired, or is it a bug?

Right now this is the design of flush-zone, it iterates over the cache
contents.  And it sets every element of the flushed zone to the expired
state.  I couldn't really delete the element at that time, because the
iterator would become invalid.

I figured it was something like that. Perhaps the man page could mention this? The entry for flush_zone says "Remove all information at or below the name from the cache" but maybe instead something like "Set the TTL to 0 for all cache entries at and below the name."

I could however, set other flags or things to the expired data.  Eg
SERVFAIL.  But then the customer receives servfail and the prefetch
happens, instead of the customer receiving the old data and a prefetch
happens, which is what there is now.

I prefer that serve-expired still actually serves expired entries if they're in the cache. I was confused because I thought I had flushed the cache, that's all.

However, there seems to be a related-but-different bug: I'm not seeing any prefetching. After the flush, no upstream query appears until after the flushed entry's original TTL elapses.



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