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Turning off async resolution at runtime
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From: Andrew Bell via curl-library <curl-library_at_lists.haxx.se>
Date: Thu, 29 Jan 2026 09:11:11 -0500
Hi,
I have an application that is making many http requests through curl. Each
request is handled by a thread. On my OS (OSX) there is a default file
descriptor limit of 256. When I make a curl request with curl_easy_perform,
it creates two pipes in addition to creating the socket on which to make
the request. It appears that these pipes are made for communication
internal to curl about async DNS resolution. This means that I'm using
three file descriptors for each request, which means get "out of file
descriptor" errors when my application has ~80 threads making curl requests.
It looks like I can disable async resolution at compile-time, which I would
think would eliminate the pipes and associated file descriptors, but I
can't control how the library was built for users. I don't see any way I
can disable this async resolution at runtime, but perhaps I'm missing
something.
Does anyone have any ideas/recommendations to eliminate the FDs being used
for DNS resolution or some other ideas on how I can reduce the likelihood
of running out of FDs when using lots of simultaneous requests?
Thanks,
Date: Thu, 29 Jan 2026 09:11:11 -0500
Hi,
I have an application that is making many http requests through curl. Each
request is handled by a thread. On my OS (OSX) there is a default file
descriptor limit of 256. When I make a curl request with curl_easy_perform,
it creates two pipes in addition to creating the socket on which to make
the request. It appears that these pipes are made for communication
internal to curl about async DNS resolution. This means that I'm using
three file descriptors for each request, which means get "out of file
descriptor" errors when my application has ~80 threads making curl requests.
It looks like I can disable async resolution at compile-time, which I would
think would eliminate the pipes and associated file descriptors, but I
can't control how the library was built for users. I don't see any way I
can disable this async resolution at runtime, but perhaps I'm missing
something.
Does anyone have any ideas/recommendations to eliminate the FDs being used
for DNS resolution or some other ideas on how I can reduce the likelihood
of running out of FDs when using lots of simultaneous requests?
Thanks,
-- Andrew Bell andrew.bell.ia_at_gmail.com
-- Unsubscribe: https://lists.haxx.se/mailman/listinfo/curl-library Etiquette: https://curl.se/mail/etiquette.htmlReceived on 2026-01-29