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Regarding async DNS resolver

From: Amit via curl-users <>
Date: Fri, 12 Jul 2019 07:05:43 +0530

> Hi All,

   Can someone please confirm if it is fine to notify DNS resolved status
from CURL to clients ?
   Please see below mail for more details.

   Thanks and Regards,
   Amit Katyal

> ---------- Forwarded message ----------
> From: Amit <>
> To:
> Cc:
> Bcc:
> Date: Tue, 9 Jul 2019 09:15:40 +0530
> Subject: Regarding async DNS resolver
> Hi All,
> This is regarding performance issue due to usage of async DNS resolver for
> MULTI interface in lib CURL.
> My application is using lib CURL (7.57 version) Muti interface with async
> DNS resolver enabled (I.e CURLRES_ASYNCH and POSIX_THREADED are defined).
> But I am facing an performance issues as there is no mechanism in CURL to
> notify DNS resolved status back to client application due to which HTTP
> request (after DNS resolution) are going out of the box with delay.
> The reason for the delay is that application is having an timer
> implementation which wakes up every 1 second and requests CURL to check all
> the ongoing requests (I.e. by calling curl_multi_perform()). So even if DNS
> was resolved within 100 msec, request will only be sent out after 1 second
> (I.e. with delay of 900 msec).
> I could see that in CURL release (7.59) a callback has been added to
> notify the clients about DNS resolution start status, but this will not
> help as I am looking for some trigger to notify about DNS resolution.
> I would like to seek your opinion/thoughts if it is good idea to implement
> a callback to notify the clients about DNS resolution ?. Also, let me know
> if there is any other available mechanism to achieve the same functionality.
> Thanks & Regards,
> Amit Katyal
> _______________________________________________
> curl-users mailing list

Received on 2019-07-12