Re: DNS data not refreshed after CURLOPT_DNS_CACHE_TIMEOUT

OK. So in the given example from man page, if I add a sleep between two
easy performs, should the application resolve the name?

  ret = curl_easy_perform(curl);
  /* in this second request, the cache will not be used if more than
     two seconds have passed since the previous name resolve */
sleep(5); /* add a sleep of five seconds, so as to force a fresh name
resolve */
  ret = curl_easy_perform(curl);

Thanks,
Narasimha

On Tue, Sep 1, 2020 at 12:11 PM Daniel Stenberg <daniel_at_haxx.se> wrote:

> On Tue, 1 Sep 2020, Narasimha M wrote:
>
> > Hence, I want to keep the connection and handle for a long time. However
> > during this time, there can be changes to the DNS server/data. I would
> like
> > the application to be agnostic to the changes to the DNS. This would
> have
> > been possible if CURL queried the DNS periodically and updated its cache
> for
> > long running handles.
>
> Sure it *could*. It's just code. It could do *anything* if we just add the
> code for it. This feature you're asking for has however not been
> implemented.
>
> > I am still not able to understand the use of CURLOPT_DNS_CACHE_TIMEOUT
> in
> > the context of a given connection which runs for a long time.
>
> curl doesn't resolve the host name AT ALL when it reuses an existing
> connection. It doesn't need to so it avoids it. Saves time and resources.
>
> The DNS cache is only used when a host name is resolved. If no resolving
> is
> done, the DNS cache is not used and therefore the timeout also has no
> meaning.
> The entry is since long removed from the DNS cache but the connection is
> still
> there - and working.
>
> > Could you please point me to any example which can illustrate
> > CURLOPT_DNS_CACHE_TIMEOUT in context of a given curl handle?
>
> How would a cache timeout even get visualized in an example? There's an
> example in the man page for the option:
> https://curl.haxx.se/libcurl/c/CURLOPT_DNS_CACHE_TIMEOUT.html
>
> --
>
> / daniel.haxx.se | Commercial curl support up to 24x7 is available!
> | Private help, bug fixes, support, ports, new features
> | https://www.wolfssl.com/contact/
>

-------------------------------------------------------------------
Unsubscribe: https://cool.haxx.se/list/listinfo/curl-library
Etiquette: https://curl.haxx.se/mail/etiquette.html
Received on 2020-09-01