Manpages - CURLOPT_DNS_CACHE_TIMEOUT.3

CURLOPT_DNS_CACHE_TIMEOUT - life-time for DNS cache entries

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_CACHE_TIMEOUT, long age);

Pass a long, this sets the timeout in seconds. Name resolves will be 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.

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.

Note that DNS entries have a “TTL” property but libcurl does not use that. This DNS cache timeout is entirely speculative that a name will resolve to the same address for a certain small amount of time into the future.

60

All

  CURL *curl = curl_easy_init();
  if(curl) {
    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);

    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 */
    ret = curl_easy_perform(curl);

    curl_easy_cleanup(curl);
  }

Always

Returns CURLE_OK

*CURLOPT_DNS_USE_GLOBAL_CACHE*(3), *CURLOPT_DNS_SERVERS*(3), *CURLOPT_RESOLVE*(3),