cURL running slow in Wordpress

Question

I have the following code in one of my Wordpress page templates:

$url = "https://xxxxxxxxxxxxxxx/";
$headers = array(
  'Accept: application/json',
  'Content-Type: application/json',
);

$args = [
  "ctype" => sanitize_text_field($_GET['ctype']),
];

if ($args['ctype'] == "test") {
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
  curl_setopt($ch, CURLOPT_USERAGENT, $_SERVER['HTTP_USER_AGENT']);
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_POST, true);
  curl_setopt($ch, CURLOPT_POSTFIELDS, wp_json_encode($args));
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
  curl_setopt($ch, CURLOPT_TIMEOUT, 2);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

  $response = json_decode(curl_exec($ch), true);

  // Check HTTP status code
  if (!curl_errno($ch)) {
    $http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE); 
    echo "HTTP Code: $http_code";
  } else {
    echo 'cURL Error: ' . curl_error($ch) . "\n";
  }
  curl_close($ch);
}

My code is executing extremely slow. I initially had CURLOPT_TIMEOUT set to 10. This was waiting for 10 seconds for the script to execute. Then when I switch it to 2, it was running quite fast but I think there is still a bigger problem.

In the if (!curl_errno($ch)) statement, it always goes to the else statement and echoes out cURL Error: Operation timed out after 2001 milliseconds with 0 bytes received. I don't really understand why it is always going into the else statement.

I have tried other cURL directives such as:

curl_setopt($ch, CURLOPT_ENCODING, 'gzip,deflate');
curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4 );
curl_setopt($ch, CURLOPT_SSL_SESSIONID_CACHE, true);
curl_setopt($ch, CURLOPT_DNS_CACHE_TIMEOUT, 3600);
curl_setopt($ch, CURLOPT_TCP_FASTOPEN, true);
curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_2_0);

but none of these seemed to have any effect.

---

Detailed timings based on curl_setopt($ch, CURLOPT_TIMEOUT, 10):

CURLINFO_TOTAL_TIME: 10s
CURLINFO_NAMELOOKUP_TIME: 0.001s
CURLINFO_CONNECT_TIME: 0.156s
CURLINFO_PRETRANSFER_TIME: 0.473s
CURLINFO_STARTTRANSFER_TIME: 0s

CURLINFO_HEADER_OUT: nothing returned

Answer 1

The timeout issue, in my case, was caused by the remote server not sending back any response. I had to fix configuration on the remote server to send back a response. That has resolved the issue.