CURLOPT_DNS_CACHE_TIMEOUT(3) Library Functions Manual
NAME
CURLOPT_DNS_CACHE_TIMEOUT - life-time for DNS cache entries
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_CACHE_TIMEOUT, long age);
DESCRIPTION
Pass a long, this sets the timeout in seconds. Name resolve results are
kept in memory and used for this number of seconds. Set to zero to
completely disable caching, or set to -1 to make the cached entries
remain forever. By default, libcurl caches this info for 60 seconds.
We recommend users not to tamper with this option unless strictly
necessary. If you do, be careful of using large values that can make
the cache size grow significantly if many different hostnames are used
within that timeout period.
The name resolve functions of various libc implementations do not
re-read name server information unless explicitly told so (for example,
by calling res_init(3)). This may cause libcurl to keep using the older
server even if DHCP has updated the server info, and this may look like
a DNS cache issue to the casual libcurl-app user.
DNS entries have a "TTL" property but libcurl does not use that. This
DNS cache timeout is entirely speculative that a name resolves to the
same address for a small amount of time into the future.
Since version 8.1.0, libcurl prunes entries from the DNS cache if it
exceeds 30,000 entries no matter which timeout value is used.
DEFAULT
60
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode res;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");
/* only reuse addresses for a short time */
curl_easy_setopt(curl, CURLOPT_DNS_CACHE_TIMEOUT, 2L);
res = curl_easy_perform(curl);
/* in this second request, the cache is not be used if more than
two seconds have passed since the previous name resolve */
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
AVAILABILITY
Added in curl 7.9.3
RETURN VALUE
Returns CURLE_OK
SEE ALSO
CURLOPT_CONNECTTIMEOUT_MS(3), CURLOPT_DNS_SERVERS(3),
CURLOPT_DNS_USE_GLOBAL_CACHE(3), CURLOPT_MAXAGE_CONN(3),
CURLOPT_RESOLVE(3)
libcurl 2024-08-05 CURLOPT_DNS_CACHE_TIMEOUT(3)
curl 8.9.1 - Generated Tue Aug 6 15:16:59 CDT 2024