Debugging in the status report needs to be more detailed.

Do you have this same issue when using HTTPRL?

Is this with the latest dev of httprl?

I wonder if FastCGI has issues with stream_select or with hanging connections. If your wondering HTTPRL is code that is inspired by AdvAgg; they both use the same principle thus just using HTTPRL will allow us to debug this faster.

Below is some debug code that I created from a quick copy paste from inside of
httprl_requirements(). If you could run it and report back the output that would be helpful.

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

ini_set('display_errors', TRUE);

    $url_path = 'admin/httprl-test';

    // Check that the menu router handler is working. If it's not working the rest
    // of the tests are pointless.
    $item = menu_get_item($url_path);


    // Test the non blocking url
    global $base_root, $base_path, $conf;
    $id = 'httprl_' . md5(mt_rand() . time());
    // Build URL to point to admin/httprl-test on this server.
    $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

    // Set the headers to point to this hostname.
    $headers = array(
      'Host' => $_SERVER['HTTP_HOST'],
    );

    // Add in the headers and set the blocking mode.
    $options = array(
      'headers' => $headers,
      'blocking' => FALSE,
      'timeout' => 6.0,
    );

    // Start the timer & Get a lock.
    timer_start($id);
    lock_acquire($id, 6);

    // Queue up the requests & execute them.
    httprl_request($url, $options);
    $requests = httprl_send_request();

    // Wait for the lock and stop the timer.
    lock_wait($id);
    $time = timer_stop($id);
    if (($time['time'] / 1000) > 5) {
      $ip = variable_get('httprl_server_addr', FALSE);
      $lasttime = '';
      $lastrequests = '';
      if (empty($ip)) {
        $lasttime = $time;
        $lastrequests = $requests;
        $conf['httprl_server_addr'] = -1;

        // If lock failed to release in time, try not using an IP when calling self.
        $id = 'httprl_' . md5(mt_rand() . time());
        // Build URL to point to admin/httprl-test on this server.


        $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

        // Set the headers to point to this hostname.
        $headers = array(
          'Host' => $_SERVER['HTTP_HOST'],
        );

        // Add in the headers and set the blocking mode.
        $options = array(
          'headers' => $headers,
          'blocking' => FALSE,
          'timeout' => 6.0,
        );

        // Start the timer & Get a lock.
        timer_start($id);
        lock_acquire($id, 6);

        // Queue up the requests & execute them.
        httprl_request($url, $options);
        $requests = httprl_send_request();

        // Wait for the lock and stop the timer.
        lock_wait($id);
        $time = timer_stop($id);
      }
      if (($time['time'] / 1000) > 5) {
        // Lock timed out and was not reset by the URL ping.
        $requirements['httprl_nonblocking'] = array('This server does not handle hanging connections.', $lastrequests, $requests);
      }
      else {
        $requirements['httprl_nonblocking'] = array('Semi-Works.', $lastrequests, $requests);
      }
    }
    else {
      $requirements['httprl_nonblocking'] = array('Works.', $requests);
    }



    $id = 'httprl_' . md5(mt_rand() . time());
    // Build URL to point to admin/httprl-test on this server.
    $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

    // Set the headers to point to this hostname.
    $headers = array(
      'Host' => $_SERVER['HTTP_HOST'],
    );

    // Add in the headers and set the blocking mode.
    $options = array(
      'headers' => $headers,
      'blocking' => TRUE,
      'timeout' => 6.0,
    );

    // Start the timer & Get a lock.
    timer_start($id);
    lock_acquire($id, 6);

    // Queue up the requests & execute them.
    httprl_request($url, $options);
    $requests = httprl_send_request();

    // Wait for the lock and stop the timer.
    lock_wait($id);
    $time = timer_stop($id);
    if (($time['time'] / 1000) > 5) {
      $ip = variable_get('httprl_server_addr', FALSE);
      $lasttime = '';
      $lastrequests = '';
      if (empty($ip)) {
        $lasttime = $time;
        $lastrequests = $requests;
        $conf['httprl_server_addr'] = -1;

        // If lock failed to release in time, try not using an IP when calling self.
        $id = 'httprl_' . md5(mt_rand() . time());
        // Build URL to point to admin/httprl-test on this server.


        $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

        // Set the headers to point to this hostname.
        $headers = array(
          'Host' => $_SERVER['HTTP_HOST'],
        );

        // Add in the headers and set the blocking mode.
        $options = array(
          'headers' => $headers,
          'blocking' => TRUE,
          'timeout' => 6.0,
        );

        // Start the timer & Get a lock.
        timer_start($id);
        lock_acquire($id, 6);

        // Queue up the requests & execute them.
        httprl_request($url, $options);
        $requests = httprl_send_request();

        // Wait for the lock and stop the timer.
        lock_wait($id);
        $time = timer_stop($id);
      }
      if (($time['time'] / 1000) > 5) {
        // Lock timed out and was not reset by the URL ping.
        $requirements['httprl_blocking'] = array('This server does not handle hanging connections.', $lastrequests, $requests);
      }
      else {
        $requirements['httprl_blocking'] = array('Semi-Works.', $lastrequests, $requests);
      }
    }
    else {
      $requirements['httprl_blocking'] = array('Works.', $requests);
    }

echo $_SERVER['GATEWAY_INTERFACE'];
echo str_replace('    ', '    ', nl2br(htmlentities(iconv('utf-8', 'utf-8//IGNORE', print_r($requirements, TRUE)), ENT_QUOTES, 'UTF-8')));

Sounds like FastCGI doesn't like stream_select(), I wonder if socket_select() will work. Will have to come up with an alt #1272542: fallback code for stream_select; cURL is next up. Do you have that installed on your server?

Its the weekend so I'll come back to this on Monday; I will be reading up here though
http://www.phpied.com/simultaneuos-http-requests-in-php-with-curl/
http://www.rustyrazorblade.com/2008/02/curl_multi_exec/
http://php.net/curl-setopt
#1033142: cURL based alternative to drupal_http_request

cURL doesn't work with non blocking requests... so going to try fsockopen from Drupal 6's drupal_http_request. Can you test this code out?

define('DRUPAL_ROOT', getcwd());

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

ini_set('display_errors', TRUE);
set_time_limit(0);


    $url_path = 'admin/httprl-test';

    // Check that the menu router handler is working. If it's not working the rest
    // of the tests are pointless.
    $item = menu_get_item($url_path);


    // Test the non blocking url
    global $base_root, $base_path, $conf;
    $id = 'httprl_' . md5(mt_rand() . time());
    // Build URL to point to admin/httprl-test on this server.
    $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

    // Set the headers to point to this hostname.
    $headers = array(
      'Host' => $_SERVER['HTTP_HOST'],
    );

    // Start the timer & Get a lock.
    timer_start($id);
    lock_acquire($id, 6);

    // Queue up the requests & execute them.
    nonblocking_drupal_http_request($url, $headers);

    // Wait for the lock and stop the timer.
    lock_wait($id);
    $time = timer_stop($id);
    if (($time['time'] / 1000) > 5) {
      $ip = variable_get('httprl_server_addr', FALSE);
      $lasttime = '';
      $lastrequests = '';
      if (empty($ip)) {
        $lasttime = $time;
        $lastrequests = $requests;
        $conf['httprl_server_addr'] = -1;

        // If lock failed to release in time, try not using an IP when calling self.
        $id = 'httprl_' . md5(mt_rand() . time());
        // Build URL to point to admin/httprl-test on this server.


        $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

        // Set the headers to point to this hostname.
        $headers = array(
          'Host' => $_SERVER['HTTP_HOST'],
        );

        // Start the timer & Get a lock.
        timer_start($id);
        lock_acquire($id, 6);

        // Queue up the requests & execute them.
        nonblocking_drupal_http_request($url, $headers);

        // Wait for the lock and stop the timer.
        lock_wait($id);
        $time = timer_stop($id);
      }
      if (($time['time'] / 1000) > 5) {
        // Lock timed out and was not reset by the URL ping.
        $requirements['httprl_nonblocking'] = array('This server does not handle hanging connections.', $lastrequests, $requests);
      }
      else {
        $requirements['httprl_nonblocking'] = array('Semi-Works.', $lastrequests, $requests);
      }
    }
    else {
      $requirements['httprl_nonblocking'] = array('Works.', $requests);
    }



    $id = 'httprl_' . md5(mt_rand() . time());
    // Build URL to point to admin/httprl-test on this server.
    $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

    // Set the headers to point to this hostname.
    $headers = array(
      'Host' => $_SERVER['HTTP_HOST'],
    );

    // Start the timer & Get a lock.
    timer_start($id);
    lock_acquire($id, 6);

    // Queue up the requests & execute them.
    nonblocking_drupal_http_request($url, $headers);

    // Wait for the lock and stop the timer.
    lock_wait($id);
    $time = timer_stop($id);
    if (($time['time'] / 1000) > 5) {
      $ip = variable_get('httprl_server_addr', FALSE);
      $lasttime = '';
      $lastrequests = '';
      if (empty($ip)) {
        $lasttime = $time;
        $lastrequests = $requests;
        $conf['httprl_server_addr'] = -1;

        // If lock failed to release in time, try not using an IP when calling self.
        $id = 'httprl_' . md5(mt_rand() . time());
        // Build URL to point to admin/httprl-test on this server.


        $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

        // Set the headers to point to this hostname.
        $headers = array(
          'Host' => $_SERVER['HTTP_HOST'],
        );

        // Start the timer & Get a lock.
        timer_start($id);
        lock_acquire($id, 6);

        // Queue up the requests & execute them.
        nonblocking_drupal_http_request($url, $headers);

        // Wait for the lock and stop the timer.
        lock_wait($id);
        $time = timer_stop($id);
      }
      if (($time['time'] / 1000) > 5) {
        // Lock timed out and was not reset by the URL ping.
        $requirements['httprl_blocking'] = array('This server does not handle hanging connections.', $lastrequests, $requests);
      }
      else {
        $requirements['httprl_blocking'] = array('Semi-Works.', $lastrequests, $requests);
      }
    }
    else {
      $requirements['httprl_blocking'] = array('Works.', $requests);
    }

echo $_SERVER['GATEWAY_INTERFACE'];
echo str_replace('    ', '    ', nl2br(htmlentities(iconv('utf-8', 'utf-8//IGNORE', print_r($requirements, TRUE)), ENT_QUOTES, 'UTF-8')));



/**
 * Perform an HTTP request.
 *
 * This is a flexible and powerful HTTP client implementation. Correctly handles
 * GET, POST, PUT or any other HTTP requests. Handles redirects.
 *
 * @param $url
 *   A string containing a fully qualified URI.
 * @param $headers
 *   An array containing an HTTP header => value pair.
 * @param $method
 *   A string defining the HTTP request to use.
 * @param $data
 *   A string containing data to include in the request.
 * @param $retry
 *   An integer representing how many times to retry the request in case of a
 *   redirect.
 * @return
 *   An object containing the HTTP request headers, response code, protocol,
 *   status message, headers, data and redirect status.
 */
function nonblocking_drupal_http_request($url, $headers = array(), $method = 'GET', $data = NULL, $retry = 3) {
  global $db_prefix;

  $result = new stdClass();

  // Parse the URL and make sure we can handle the schema.
  $uri = parse_url($url);

  if ($uri == FALSE) {
    $result->error = 'unable to parse URL';
    $result->code = -1001;
    return $result;
  }

  if (!isset($uri['scheme'])) {
    $result->error = 'missing schema';
    $result->code = -1002;
    return $result;
  }

  switch ($uri['scheme']) {
    case 'http':
    case 'feed':
      $port = isset($uri['port']) ? $uri['port'] : 80;
      $host = $uri['host'] . ($port != 80 ? ':'. $port : '');
      $fp = @fsockopen($uri['host'], $port, $errno, $errstr, 15);
      break;
    case 'https':
      // Note: Only works for PHP 4.3 compiled with OpenSSL.
      $port = isset($uri['port']) ? $uri['port'] : 443;
      $host = $uri['host'] . ($port != 443 ? ':'. $port : '');
      $fp = @fsockopen('ssl://'. $uri['host'], $port, $errno, $errstr, 20);
      break;
    default:
      $result->error = 'invalid schema '. $uri['scheme'];
      $result->code = -1003;
      return $result;
  }

  // Make sure the socket opened properly.
  if (!$fp) {
    // When a network error occurs, we use a negative number so it does not
    // clash with the HTTP status codes.
    $result->code = -$errno;
    $result->error = trim($errstr);

    // Mark that this request failed. This will trigger a check of the web
    // server's ability to make outgoing HTTP requests the next time that
    // requirements checking is performed.
    // @see system_requirements()
    variable_set('drupal_http_request_fails', TRUE);

    return $result;
  }

  // Construct the path to act on.
  $path = isset($uri['path']) ? $uri['path'] : '/';
  if (isset($uri['query'])) {
    $path .= '?'. $uri['query'];
  }

  // Create HTTP request.
  $defaults = array(
    // RFC 2616: "non-standard ports MUST, default ports MAY be included".
    // We don't add the port to prevent from breaking rewrite rules checking the
    // host that do not take into account the port number.
    'Host' => "Host: $host",
    'User-Agent' => 'User-Agent: Drupal (+http://drupal.org/)',
  );

  // Only add Content-Length if we actually have any content or if it is a POST
  // or PUT request. Some non-standard servers get confused by Content-Length in
  // at least HEAD/GET requests, and Squid always requires Content-Length in
  // POST/PUT requests.
  $content_length = strlen($data);
  if ($content_length > 0 || $method == 'POST' || $method == 'PUT') {
    $defaults['Content-Length'] = 'Content-Length: '. $content_length;
  }

  // If the server url has a user then attempt to use basic authentication
  if (isset($uri['user'])) {
    $defaults['Authorization'] = 'Authorization: Basic '. base64_encode($uri['user'] . (!empty($uri['pass']) ? ":". $uri['pass'] : ''));
  }

  // If the database prefix is being used by SimpleTest to run the tests in a copied
  // database then set the user-agent header to the database prefix so that any
  // calls to other Drupal pages will run the SimpleTest prefixed database. The
  // user-agent is used to ensure that multiple testing sessions running at the
  // same time won't interfere with each other as they would if the database
  // prefix were stored statically in a file or database variable.
  if (is_string($db_prefix) && preg_match("/^simpletest\d+$/", $db_prefix, $matches)) {
    $defaults['User-Agent'] = 'User-Agent: ' . drupal_generate_test_ua($matches[0]);
  }

  foreach ($headers as $header => $value) {
    $defaults[$header] = $header .': '. $value;
  }

  $request = $method .' '. $path ." HTTP/1.0\r\n";
  $request .= implode("\r\n", $defaults);
  $request .= "\r\n\r\n";
  $request .= $data;

  $result->request = $request;

  fwrite($fp, $request);
  fclose($fp);

  return $result;
}

How are you testing the code? I defined a new function called nonblocking_drupal_http_request in the code block above; and why is it inside of advagg.install? Copy the code block into something like test.php in the drupal web root, next to index.php.

Looks like FastCGI kills PHP when the connection is closed... I have 2 more tests for you to try:

define('DRUPAL_ROOT', getcwd());

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

ini_set('display_errors', TRUE);
set_time_limit(0);


    $url_path = 'admin/httprl-test';

    // Check that the menu router handler is working. If it's not working the rest
    // of the tests are pointless.
    $item = menu_get_item($url_path);


    // Test the non blocking url
    global $base_root, $base_path, $conf;
    $id = 'httprl_' . md5(mt_rand() . time());
    // Build URL to point to admin/httprl-test on this server.
    $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

    // Set the headers to point to this hostname.
    $headers = array(
      'Host' => $_SERVER['HTTP_HOST'],
    );

    // Start the timer & Get a lock.
    timer_start($id);
    lock_acquire($id, 6);

    // Queue up the requests & execute them.
    nonblocking_drupal_http_request($url, $headers);

    // Wait for the lock and stop the timer.
    lock_wait($id);
    $time = timer_stop($id);
    if (($time['time'] / 1000) > 5) {
      $ip = variable_get('httprl_server_addr', FALSE);
      $lasttime = '';
      $lastrequests = '';
      if (empty($ip)) {
        $lasttime = $time;
        $lastrequests = $requests;
        $conf['httprl_server_addr'] = -1;

        // If lock failed to release in time, try not using an IP when calling self.
        $id = 'httprl_' . md5(mt_rand() . time());
        // Build URL to point to admin/httprl-test on this server.


        $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

        // Set the headers to point to this hostname.
        $headers = array(
          'Host' => $_SERVER['HTTP_HOST'],
        );

        // Start the timer & Get a lock.
        timer_start($id);
        lock_acquire($id, 6);

        // Queue up the requests & execute them.
        nonblocking_drupal_http_request($url, $headers);

        // Wait for the lock and stop the timer.
        lock_wait($id);
        $time = timer_stop($id);
      }
      if (($time['time'] / 1000) > 5) {
        // Lock timed out and was not reset by the URL ping.
        $requirements['httprl_nonblocking'] = array('This server does not handle hanging connections.', $lastrequests, $requests);
      }
      else {
        $requirements['httprl_nonblocking'] = array('Semi-Works.', $lastrequests, $requests);
      }
    }
    else {
      $requirements['httprl_nonblocking'] = array('Works.', $requests);
    }



    $id = 'httprl_' . md5(mt_rand() . time());
    // Build URL to point to admin/httprl-test on this server.
    $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

    // Set the headers to point to this hostname.
    $headers = array(
      'Host' => $_SERVER['HTTP_HOST'],
    );

    // Start the timer & Get a lock.
    timer_start($id);
    lock_acquire($id, 6);

    // Queue up the requests & execute them.
    nonblocking_drupal_http_request($url, $headers);

    // Wait for the lock and stop the timer.
    lock_wait($id);
    $time = timer_stop($id);
    if (($time['time'] / 1000) > 5) {
      $ip = variable_get('httprl_server_addr', FALSE);
      $lasttime = '';
      $lastrequests = '';
      if (empty($ip)) {
        $lasttime = $time;
        $lastrequests = $requests;
        $conf['httprl_server_addr'] = -1;

        // If lock failed to release in time, try not using an IP when calling self.
        $id = 'httprl_' . md5(mt_rand() . time());
        // Build URL to point to admin/httprl-test on this server.


        $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

        // Set the headers to point to this hostname.
        $headers = array(
          'Host' => $_SERVER['HTTP_HOST'],
        );

        // Start the timer & Get a lock.
        timer_start($id);
        lock_acquire($id, 6);

        // Queue up the requests & execute them.
        nonblocking_drupal_http_request($url, $headers);

        // Wait for the lock and stop the timer.
        lock_wait($id);
        $time = timer_stop($id);
      }
      if (($time['time'] / 1000) > 5) {
        // Lock timed out and was not reset by the URL ping.
        $requirements['httprl_blocking'] = array('This server does not handle hanging connections.', $lastrequests, $requests);
      }
      else {
        $requirements['httprl_blocking'] = array('Semi-Works.', $lastrequests, $requests);
      }
    }
    else {
      $requirements['httprl_blocking'] = array('Works.', $requests);
    }

echo $_SERVER['GATEWAY_INTERFACE'];
echo str_replace('    ', '    ', nl2br(htmlentities(iconv('utf-8', 'utf-8//IGNORE', print_r($requirements, TRUE)), ENT_QUOTES, 'UTF-8')));



/**
 * Perform an HTTP request.
 *
 * This is a flexible and powerful HTTP client implementation. Correctly handles
 * GET, POST, PUT or any other HTTP requests. Handles redirects.
 *
 * @param $url
 *   A string containing a fully qualified URI.
 * @param $headers
 *   An array containing an HTTP header => value pair.
 * @param $method
 *   A string defining the HTTP request to use.
 * @param $data
 *   A string containing data to include in the request.
 * @param $retry
 *   An integer representing how many times to retry the request in case of a
 *   redirect.
 * @return
 *   An object containing the HTTP request headers, response code, protocol,
 *   status message, headers, data and redirect status.
 */
function nonblocking_drupal_http_request($url, $headers = array(), $method = 'GET', $data = NULL, $retry = 3) {
  global $db_prefix;

  $result = new stdClass();

  // Parse the URL and make sure we can handle the schema.
  $uri = parse_url($url);

  if ($uri == FALSE) {
    $result->error = 'unable to parse URL';
    $result->code = -1001;
    return $result;
  }

  if (!isset($uri['scheme'])) {
    $result->error = 'missing schema';
    $result->code = -1002;
    return $result;
  }

  switch ($uri['scheme']) {
    case 'http':
    case 'feed':
      $port = isset($uri['port']) ? $uri['port'] : 80;
      $host = $uri['host'] . ($port != 80 ? ':'. $port : '');
      $fp = @fsockopen($uri['host'], $port, $errno, $errstr, 15);
      break;
    case 'https':
      // Note: Only works for PHP 4.3 compiled with OpenSSL.
      $port = isset($uri['port']) ? $uri['port'] : 443;
      $host = $uri['host'] . ($port != 443 ? ':'. $port : '');
      $fp = @fsockopen('ssl://'. $uri['host'], $port, $errno, $errstr, 20);
      break;
    default:
      $result->error = 'invalid schema '. $uri['scheme'];
      $result->code = -1003;
      return $result;
  }

  // Make sure the socket opened properly.
  if (!$fp) {
    // When a network error occurs, we use a negative number so it does not
    // clash with the HTTP status codes.
    $result->code = -$errno;
    $result->error = trim($errstr);

    // Mark that this request failed. This will trigger a check of the web
    // server's ability to make outgoing HTTP requests the next time that
    // requirements checking is performed.
    // @see system_requirements()
    variable_set('drupal_http_request_fails', TRUE);

    return $result;
  }

  // Construct the path to act on.
  $path = isset($uri['path']) ? $uri['path'] : '/';
  if (isset($uri['query'])) {
    $path .= '?'. $uri['query'];
  }

  // Create HTTP request.
  $defaults = array(
    // RFC 2616: "non-standard ports MUST, default ports MAY be included".
    // We don't add the port to prevent from breaking rewrite rules checking the
    // host that do not take into account the port number.
    'Host' => "Host: $host",
    'User-Agent' => 'User-Agent: Drupal (+http://drupal.org/)',
  );

  // Only add Content-Length if we actually have any content or if it is a POST
  // or PUT request. Some non-standard servers get confused by Content-Length in
  // at least HEAD/GET requests, and Squid always requires Content-Length in
  // POST/PUT requests.
  $content_length = strlen($data);
  if ($content_length > 0 || $method == 'POST' || $method == 'PUT') {
    $defaults['Content-Length'] = 'Content-Length: '. $content_length;
  }

  // If the server url has a user then attempt to use basic authentication
  if (isset($uri['user'])) {
    $defaults['Authorization'] = 'Authorization: Basic '. base64_encode($uri['user'] . (!empty($uri['pass']) ? ":". $uri['pass'] : ''));
  }

  // If the database prefix is being used by SimpleTest to run the tests in a copied
  // database then set the user-agent header to the database prefix so that any
  // calls to other Drupal pages will run the SimpleTest prefixed database. The
  // user-agent is used to ensure that multiple testing sessions running at the
  // same time won't interfere with each other as they would if the database
  // prefix were stored statically in a file or database variable.
  if (is_string($db_prefix) && preg_match("/^simpletest\d+$/", $db_prefix, $matches)) {
    $defaults['User-Agent'] = 'User-Agent: ' . drupal_generate_test_ua($matches[0]);
  }

  foreach ($headers as $header => $value) {
    $defaults[$header] = $header .': '. $value;
  }

  $request = $method .' '. $path ." HTTP/1.0\r\n";
  $request .= implode("\r\n", $defaults);
  $request .= "\r\n\r\n";
  $request .= $data;

  $result->request = $request;

  fwrite($fp, $request);
  $result->data = fread($fp, 1024);
  fclose($fp);

  return $result;
}

define('DRUPAL_ROOT', getcwd());

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

ini_set('display_errors', TRUE);
set_time_limit(0);


    $url_path = 'admin/httprl-test';

    // Check that the menu router handler is working. If it's not working the rest
    // of the tests are pointless.
    $item = menu_get_item($url_path);


    // Test the non blocking url
    global $base_root, $base_path, $conf;
    $id = 'httprl_' . md5(mt_rand() . time());
    // Build URL to point to admin/httprl-test on this server.
    $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

    // Set the headers to point to this hostname.
    $headers = array(
      'Host' => $_SERVER['HTTP_HOST'],
    );

    // Start the timer & Get a lock.
    timer_start($id);
    lock_acquire($id, 6);

    // Queue up the requests & execute them.
    nonblocking_drupal_http_request($url, $headers);

    // Wait for the lock and stop the timer.
    lock_wait($id);
    $time = timer_stop($id);
    if (($time['time'] / 1000) > 5) {
      $ip = variable_get('httprl_server_addr', FALSE);
      $lasttime = '';
      $lastrequests = '';
      if (empty($ip)) {
        $lasttime = $time;
        $lastrequests = $requests;
        $conf['httprl_server_addr'] = -1;

        // If lock failed to release in time, try not using an IP when calling self.
        $id = 'httprl_' . md5(mt_rand() . time());
        // Build URL to point to admin/httprl-test on this server.


        $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

        // Set the headers to point to this hostname.
        $headers = array(
          'Host' => $_SERVER['HTTP_HOST'],
        );

        // Start the timer & Get a lock.
        timer_start($id);
        lock_acquire($id, 6);

        // Queue up the requests & execute them.
        nonblocking_drupal_http_request($url, $headers);

        // Wait for the lock and stop the timer.
        lock_wait($id);
        $time = timer_stop($id);
      }
      if (($time['time'] / 1000) > 5) {
        // Lock timed out and was not reset by the URL ping.
        $requirements['httprl_nonblocking'] = array('This server does not handle hanging connections.', $lastrequests, $requests);
      }
      else {
        $requirements['httprl_nonblocking'] = array('Semi-Works.', $lastrequests, $requests);
      }
    }
    else {
      $requirements['httprl_nonblocking'] = array('Works.', $requests);
    }



    $id = 'httprl_' . md5(mt_rand() . time());
    // Build URL to point to admin/httprl-test on this server.
    $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

    // Set the headers to point to this hostname.
    $headers = array(
      'Host' => $_SERVER['HTTP_HOST'],
    );

    // Start the timer & Get a lock.
    timer_start($id);
    lock_acquire($id, 6);

    // Queue up the requests & execute them.
    nonblocking_drupal_http_request($url, $headers);

    // Wait for the lock and stop the timer.
    lock_wait($id);
    $time = timer_stop($id);
    if (($time['time'] / 1000) > 5) {
      $ip = variable_get('httprl_server_addr', FALSE);
      $lasttime = '';
      $lastrequests = '';
      if (empty($ip)) {
        $lasttime = $time;
        $lastrequests = $requests;
        $conf['httprl_server_addr'] = -1;

        // If lock failed to release in time, try not using an IP when calling self.
        $id = 'httprl_' . md5(mt_rand() . time());
        // Build URL to point to admin/httprl-test on this server.


        $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

        // Set the headers to point to this hostname.
        $headers = array(
          'Host' => $_SERVER['HTTP_HOST'],
        );

        // Start the timer & Get a lock.
        timer_start($id);
        lock_acquire($id, 6);

        // Queue up the requests & execute them.
        nonblocking_drupal_http_request($url, $headers);

        // Wait for the lock and stop the timer.
        lock_wait($id);
        $time = timer_stop($id);
      }
      if (($time['time'] / 1000) > 5) {
        // Lock timed out and was not reset by the URL ping.
        $requirements['httprl_blocking'] = array('This server does not handle hanging connections.', $lastrequests, $requests);
      }
      else {
        $requirements['httprl_blocking'] = array('Semi-Works.', $lastrequests, $requests);
      }
    }
    else {
      $requirements['httprl_blocking'] = array('Works.', $requests);
    }

echo $_SERVER['GATEWAY_INTERFACE'];
echo str_replace('    ', '    ', nl2br(htmlentities(iconv('utf-8', 'utf-8//IGNORE', print_r($requirements, TRUE)), ENT_QUOTES, 'UTF-8')));



/**
 * Perform an HTTP request.
 *
 * This is a flexible and powerful HTTP client implementation. Correctly handles
 * GET, POST, PUT or any other HTTP requests. Handles redirects.
 *
 * @param $url
 *   A string containing a fully qualified URI.
 * @param $headers
 *   An array containing an HTTP header => value pair.
 * @param $method
 *   A string defining the HTTP request to use.
 * @param $data
 *   A string containing data to include in the request.
 * @param $retry
 *   An integer representing how many times to retry the request in case of a
 *   redirect.
 * @return
 *   An object containing the HTTP request headers, response code, protocol,
 *   status message, headers, data and redirect status.
 */
function nonblocking_drupal_http_request($url, $headers = array(), $method = 'GET', $data = NULL, $retry = 3) {
  global $db_prefix;

  $result = new stdClass();

  // Parse the URL and make sure we can handle the schema.
  $uri = parse_url($url);

  if ($uri == FALSE) {
    $result->error = 'unable to parse URL';
    $result->code = -1001;
    return $result;
  }

  if (!isset($uri['scheme'])) {
    $result->error = 'missing schema';
    $result->code = -1002;
    return $result;
  }

  switch ($uri['scheme']) {
    case 'http':
    case 'feed':
      $port = isset($uri['port']) ? $uri['port'] : 80;
      $host = $uri['host'] . ($port != 80 ? ':'. $port : '');
      $fp = @fsockopen($uri['host'], $port, $errno, $errstr, 15);
      break;
    case 'https':
      // Note: Only works for PHP 4.3 compiled with OpenSSL.
      $port = isset($uri['port']) ? $uri['port'] : 443;
      $host = $uri['host'] . ($port != 443 ? ':'. $port : '');
      $fp = @fsockopen('ssl://'. $uri['host'], $port, $errno, $errstr, 20);
      break;
    default:
      $result->error = 'invalid schema '. $uri['scheme'];
      $result->code = -1003;
      return $result;
  }

  // Make sure the socket opened properly.
  if (!$fp) {
    // When a network error occurs, we use a negative number so it does not
    // clash with the HTTP status codes.
    $result->code = -$errno;
    $result->error = trim($errstr);

    // Mark that this request failed. This will trigger a check of the web
    // server's ability to make outgoing HTTP requests the next time that
    // requirements checking is performed.
    // @see system_requirements()
    variable_set('drupal_http_request_fails', TRUE);

    return $result;
  }

  // Construct the path to act on.
  $path = isset($uri['path']) ? $uri['path'] : '/';
  if (isset($uri['query'])) {
    $path .= '?'. $uri['query'];
  }

  // Create HTTP request.
  $defaults = array(
    // RFC 2616: "non-standard ports MUST, default ports MAY be included".
    // We don't add the port to prevent from breaking rewrite rules checking the
    // host that do not take into account the port number.
    'Host' => "Host: $host",
    'User-Agent' => 'User-Agent: Drupal (+http://drupal.org/)',
  );

  // Only add Content-Length if we actually have any content or if it is a POST
  // or PUT request. Some non-standard servers get confused by Content-Length in
  // at least HEAD/GET requests, and Squid always requires Content-Length in
  // POST/PUT requests.
  $content_length = strlen($data);
  if ($content_length > 0 || $method == 'POST' || $method == 'PUT') {
    $defaults['Content-Length'] = 'Content-Length: '. $content_length;
  }

  // If the server url has a user then attempt to use basic authentication
  if (isset($uri['user'])) {
    $defaults['Authorization'] = 'Authorization: Basic '. base64_encode($uri['user'] . (!empty($uri['pass']) ? ":". $uri['pass'] : ''));
  }

  // If the database prefix is being used by SimpleTest to run the tests in a copied
  // database then set the user-agent header to the database prefix so that any
  // calls to other Drupal pages will run the SimpleTest prefixed database. The
  // user-agent is used to ensure that multiple testing sessions running at the
  // same time won't interfere with each other as they would if the database
  // prefix were stored statically in a file or database variable.
  if (is_string($db_prefix) && preg_match("/^simpletest\d+$/", $db_prefix, $matches)) {
    $defaults['User-Agent'] = 'User-Agent: ' . drupal_generate_test_ua($matches[0]);
  }

  foreach ($headers as $header => $value) {
    $defaults[$header] = $header .': '. $value;
  }

  $request = $method .' '. $path ." HTTP/1.0\r\n";
  $request .= implode("\r\n", $defaults);
  $request .= "\r\n\r\n";
  $request .= $data;

  $result->request = $request;

  fwrite($fp, $request);

  return $result;
}

hmm lets try something a little more standard. This is using drupal_http_request(). Lets make sure this works. If this doesn't work then drupal wouldn't pass the system install requirements (system_check_http_request())

define('DRUPAL_ROOT', getcwd());

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

ini_set('display_errors', TRUE);
set_time_limit(0);


    $url_path = 'admin/httprl-test';

    // Check that the menu router handler is working. If it's not working the rest
    // of the tests are pointless.
    $item = menu_get_item($url_path);


    // Test the non blocking url
    global $base_root, $base_path, $conf;
    $id = 'httprl_' . md5(mt_rand() . time());
    // Build URL to point to admin/httprl-test on this server.
    $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

    // Set the headers to point to this hostname.
    $headers = array(
      'Host' => $_SERVER['HTTP_HOST'],
    );

    // Start the timer & Get a lock.
    timer_start($id);
    lock_acquire($id, 6);

    // Queue up the requests & execute them.
    drupal_http_request($url, $headers);

    // Wait for the lock and stop the timer.
    lock_wait($id);
    $time = timer_stop($id);
    if (($time['time'] / 1000) > 5) {
      $ip = variable_get('httprl_server_addr', FALSE);
      $lasttime = '';
      $lastrequests = '';
      if (empty($ip)) {
        $lasttime = $time;
        $lastrequests = $requests;
        $conf['httprl_server_addr'] = -1;

        // If lock failed to release in time, try not using an IP when calling self.
        $id = 'httprl_' . md5(mt_rand() . time());
        // Build URL to point to admin/httprl-test on this server.


        $url = httprl_build_url_self($url_path . '?key=' . md5(drupal_get_private_key()) . '&id=' . $id, TRUE);

        // Set the headers to point to this hostname.
        $headers = array(
          'Host' => $_SERVER['HTTP_HOST'],
        );

        // Start the timer & Get a lock.
        timer_start($id);
        lock_acquire($id, 6);

        // Queue up the requests & execute them.
        drupal_http_request($url, $headers);

        // Wait for the lock and stop the timer.
        lock_wait($id);
        $time = timer_stop($id);
      }
      if (($time['time'] / 1000) > 5) {
        // Lock timed out and was not reset by the URL ping.
        $requirements['drupal_http_request'] = array('This server does not handle hanging connections.', $lastrequests, $requests);
      }
      else {
        $requirements['drupal_http_request'] = array('Semi-Works.', $lastrequests, $requests);
      }
    }
    else {
      $requirements['drupal_http_request'] = array('Works.', $requests);
    }


echo $_SERVER['GATEWAY_INTERFACE'];
echo str_replace('    ', '    ', nl2br(htmlentities(iconv('utf-8', 'utf-8//IGNORE', print_r($requirements, TRUE)), ENT_QUOTES, 'UTF-8')));
$x = system_check_http_request();
echo serialize($x);

What happens when you do this?

define('DRUPAL_ROOT', getcwd());

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

ini_set('display_errors', TRUE);
set_time_limit(120);

$x = system_check_http_request();
echo serialize($x);

http://api.drupal.org/api/drupal/modules--system--system.module/function...

There is something wrong with that setup (FastCGI) if Drupal Core doesn't work with it. This might help
http://drupal.org/node/588186
If it's still an issue I would jump on IRC and see what people say about how to fix it.

I've attached a patch that adds in better debugging for httprl on the status page.

Above patch has been committed to HTTPRL. This is not an issue with AdvAgg; HTTPRL has been improved to help with the diagnosis of HTTP request errors.