Demonstration: Old connections are re-used when they shouldn't be

test.c

#include <curl/curl.h>
#include <unistd.h>

int main(int argc, char **argv) {
  const long maxage_conn = 1L;

  curl_global_init(CURL_GLOBAL_ALL);

  CURL *easy = curl_easy_init();
  curl_easy_setopt(easy, CURLOPT_URL, "https://httpbin.org/get");
  curl_easy_setopt(easy, CURLOPT_HTTPGET, 1);
  curl_easy_setopt(easy, CURLOPT_VERBOSE, 1);
  // Connections should become too old for re-use after 1 second.
  curl_easy_setopt(easy, CURLOPT_MAXAGE_CONN, maxage_conn);

  CURLcode code = curl_easy_perform(easy);
  if (code != CURLE_OK) return 1;

  printf(">>> Sleep for 5 seconds...\n");
  usleep(5000000);

  printf(">>> Should not re-use previous host connection from cache.\n");
  printf(">>> In curl verbose logs, we should see: \"Too old connection (5 seconds), disconnect it\"\n");
  printf(">>> Instead, we will see that it reuses the existing connection.\n");
  curl_easy_reset(easy);
  curl_easy_setopt(easy, CURLOPT_URL, "https://httpbin.org/get");
  curl_easy_setopt(easy, CURLOPT_HTTPGET, 1);
  curl_easy_setopt(easy, CURLOPT_VERBOSE, 1);
  curl_easy_setopt(easy, CURLOPT_MAXAGE_CONN, maxage_conn);
  code = curl_easy_perform(easy);
  if (code != CURLE_OK) return 1;

  curl_easy_cleanup(easy);
  curl_global_cleanup();
  return 0;
}