quickjs-tart

quickjs-based runtime for wallet-core logic
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CURLOPT_DNS_CACHE_TIMEOUT.md (2491B)

      1 ---
      2 c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
      3 SPDX-License-Identifier: curl
      4 Title: CURLOPT_DNS_CACHE_TIMEOUT
      5 Section: 3
      6 Source: libcurl
      7 See-also:
      8   - CURLOPT_CONNECTTIMEOUT_MS (3)
      9   - CURLOPT_DNS_SERVERS (3)
     10   - CURLOPT_DNS_USE_GLOBAL_CACHE (3)
     11   - CURLOPT_MAXAGE_CONN (3)
     12   - CURLOPT_RESOLVE (3)
     13 Protocol:
     14   - All
     15 Added-in: 7.9.3
     16 ---
     17 
     18 # NAME
     19 
     20 CURLOPT_DNS_CACHE_TIMEOUT - life-time for DNS cache entries
     21 
     22 # SYNOPSIS
     23 
     24 ~~~c
     25 #include <curl/curl.h>
     26 
     27 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_CACHE_TIMEOUT, long age);
     28 ~~~
     29 
     30 # DESCRIPTION
     31 
     32 Pass a long, this sets the timeout in seconds. Name resolve results are kept
     33 in memory and used for this number of seconds. Set to zero to completely
     34 disable caching, or set to -1 to make the cached entries remain forever. By
     35 default, libcurl caches this info for 60 seconds.
     36 
     37 We recommend users not to tamper with this option unless strictly necessary.
     38 If you do, be careful of using large values that can make the cache size grow
     39 significantly if many different hostnames are used within that timeout period.
     40 
     41 The name resolve functions of various libc implementations do not re-read name
     42 server information unless explicitly told so (for example, by calling
     43 *res_init(3)*). This may cause libcurl to keep using the older server even
     44 if DHCP has updated the server info, and this may look like a DNS cache issue
     45 to the casual libcurl-app user.
     46 
     47 DNS entries have a "TTL" property but libcurl does not use that. This DNS
     48 cache timeout is entirely speculative that a name resolves to the same address
     49 for a small amount of time into the future.
     50 
     51 Since version 8.1.0, libcurl prunes entries from the DNS cache if it exceeds
     52 30,000 entries no matter which timeout value is used.
     53 
     54 # DEFAULT
     55 
     56 60
     57 
     58 # %PROTOCOLS%
     59 
     60 # EXAMPLE
     61 
     62 ~~~c
     63 int main(void)
     64 {
     65   CURL *curl = curl_easy_init();
     66   if(curl) {
     67     CURLcode res;
     68     curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");
     69 
     70     /* only reuse addresses for a short time */
     71     curl_easy_setopt(curl, CURLOPT_DNS_CACHE_TIMEOUT, 2L);
     72 
     73     res = curl_easy_perform(curl);
     74 
     75     /* in this second request, the cache is not be used if more than
     76        two seconds have passed since the previous name resolve */
     77     res = curl_easy_perform(curl);
     78 
     79     curl_easy_cleanup(curl);
     80   }
     81 }
     82 ~~~
     83 
     84 # %AVAILABILITY%
     85 
     86 # RETURN VALUE
     87 
     88 curl_easy_setopt(3) returns a CURLcode indicating success or error.
     89 
     90 CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
     91 libcurl-errors(3).