[squid-dev] [RFC] dns_wait_for_all

[Amos Jeffries]

On 15/09/2016 8:15 a.m., Alex Rousskov wrote:
> 
> Any better ideas or objections to adding dns_wait_for_all?
> 

In principle okay. However, I was intending to redesign the object we
store DNS RR results in to achieve this is a more useful way. Such that
instead of returning an array of IP addresses it returned an object
storing the Query label, then a chain of RR objects for that label.

That would give several other useful benefits beyond that speedup:

* slow DNS responses could add to the chain while earlier results are
still in Async queue pending delivery to a caller.
 - this would obsolete the need for dns_wait_for_all to be configurable.
Always respond on first result and append data if it comes in early enough.

* ip/fqdn caches can store older data up to some timeout in TTL / LRU
sequence.
 - resolving many DNS rotation issues, including certain type of Host
verify failures.
 - merging the IP and FQDN caches ??

* extensibility of RR type the DNS could lookup and present the callers.
 - needed by DANE and SRV lookups.

* one less memcpy cycle per IP address returned by DNS.
 - paid for by more chain dereferencing overheads.

Amos