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HTTP PARALLEL REQUEST & THREADING LIBRARY MODULE
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CONTENTS OF THIS FILE
---------------------

 * About HTTPRL
 * Requirements
 * Configuration
 * API Overview
 * Technical Details
 * Code Examples


ABOUT HTTPRL
------------

http://drupal.org/project/httprl

HTTPRL is a flexible and powerful HTTP client implementation. Correctly handles
GET, POST, PUT or any other HTTP requests & the sending of data. Issue blocking
or non-blocking requests in parallel. Set timeouts, max simultaneous connection
limits, chunk size, and max redirects to follow. Can handle data with
content-encoding and transfer-encoding headers set. Correctly follows
redirects. Option to forward the referrer when a redirect is found. Cookie
extraction and parsing into key value pairs. Can multipart encode data so files
can easily be sent in a HTTP request.


REQUIREMENTS
------------

Requires PHP 5. The following functions must be available on the server:
 * stream_socket_client
 * stream_select
 * stream_set_blocking
 * stream_get_meta_data
 * stream_socket_get_name
Some hosting providers disable these functions; but they do come standard with
PHP 5.


CONFIGURATION
-------------

Settings page is located at:
6.x: admin/settings/httprl
7.x: admin/config/development/httprl

 * IP Address to send all self server requests to. If left blank it will use the
   same server as the request. If set to -1 it will use the host name instead of
   an IP address. This controls the output of httprl_build_url_self().


API OVERVIEW
------------

Issue HTTP Requests:
httprl_build_url_self()
 - Helper function to build an URL for asynchronous requests to self.
httprl_request()
 - Queue up a HTTP request in httprl_send_request().
httprl_send_request()
 - Perform many HTTP requests.

Create and use a thread:
httprl_queue_background_callback()
 - Queue a special HTTP request (used for threading) in httprl_send_request().

Other Functions:
httprl_background_processing()
 - Output text, close connection, continue processing in the background.
httprl_strlen()
 - Get the length of a string in bytes.
httprl_glue_url()
 - Alt to http_build_url().
httprl_get_server_schema()
 - Return the server schema (http or https).
httprl_pr()
 - Pretty print data.
httprl_fast403()
 - Issue a 403 and exit.


TECHNICAL DETAILS
-----------------

Using stream_select() HTTPRL will send http requests out in parallel. These
requests can be made in a blocking or non-blocking way. Blocking will wait for
the http response; Non-Blocking will close the connection not waiting for the
response back. The API for httprl is similar to the Drupal 7 version of
drupal_http_request().

HTTPRL can be used independent of drupal. For basic operations it doesn't
require any built in drupal functions.


CODE EXAMPLES
-------------

**Simple HTTP**

Request http://drupal.org/.

    <?php
    // Queue up the request.
    httprl_request('http://drupal.org/');
    // Execute request.
    $request = httprl_send_request();

    // Echo out the results.
    echo httprl_pr($request);
    ?>


Request this servers own front page & the node page.

    <?php
    // Build URL to point to front page of this server.
    $url_front = httprl_build_url_self();
    // Build URL to point to /node on this server.
    $url_node = httprl_build_url_self('node');
    // Queue up the requests.
    httprl_request($url_front);
    httprl_request($url_node);
    // Execute requests.
    $request = httprl_send_request();

    // Echo out the results.
    echo httprl_pr($request);
    ?>


**Non Blocking HTTP Operations**

Request 10 URLs in a non blocking manner on this server. Checkout watchdog as
this should generate 10 404s and the $request object won't contain much info.

    <?php
    // Set the blocking mode.
    $options = array(
      'blocking' => FALSE,
    );
    // Queue up the requests.
    $max = 10;
    for ($i=1; $i <= $max; $i++) {
      // Build URL to a page that doesn't exist.
      $url = httprl_build_url_self('asdf-asdf-asdf-' . $i);
      httprl_request($url, $options);
    }
    // Execute requests.
    $request = httprl_send_request();

    // Echo out the results.
    echo httprl_pr($request);
    ?>


Request 10 URLs in a non blocking manner with one httprl_request() call. These
URLs will all have the same options.

    <?php
    // Set the blocking mode.
    $options = array(
      'method' => 'HEAD',
      'blocking' => FALSE,
    );
    // Queue up the requests.
    $max = 10;
    $urls = array();
    for ($i=1; $i <= $max; $i++) {
      // Build URL to a page that doesn't exist.
      $urls[] = httprl_build_url_self('asdf-asdf-asdf-' . $i);
    }
    // Queue up the requests.
    httprl_request($urls, $options);
    // Execute requests.
    $request = httprl_send_request();

    // Echo out the results.
    echo httprl_pr($request);
    ?>


Request 1000 URLs in a non blocking manner with one httprl_request() call. These
URLs will all have the same options. This will saturate the server and any
connections that couldn't be made will be dropped.

    <?php
    // Set the blocking mode.
    $options = array(
      'method' => 'HEAD',
      'blocking' => FALSE,
    );
    // Queue up the requests.
    $max = 1000;
    $urls = array();
    for ($i=1; $i <= $max; $i++) {
      // Build URL to a page that doesn't exist.
      $urls[] = httprl_build_url_self('asdf-asdf-asdf-' . $i);
    }
    // Queue up the requests.
    httprl_request($urls, $options);
    // Execute requests.
    $request = httprl_send_request();

    // Echo out the results.
    echo httprl_pr($request);
    ?>


Request 1000 URLs in a non blocking manner with one httprl_request() call. These
URLs will all have the same options. This will saturate the server. All 1000
requests will eventually hit the server due to it waiting for the connection to
be established; `async_connect` is FALSE.

    <?php
    // Set the blocking mode.
    $options = array(
      'method' => 'HEAD',
      'blocking' => FALSE,
      'async_connect' => FALSE,
    );
    // Queue up the requests.
    $max = 1000;
    $urls = array();
    for ($i=1; $i <= $max; $i++) {
      // Build URL to a page that doesn't exist.
      $urls[] = httprl_build_url_self('asdf-asdf-asdf-' . $i);
    }
    // Queue up the requests.
    httprl_request($urls, $options);
    // Execute requests.
    $request = httprl_send_request();

    // Echo out the results.
    echo httprl_pr($request);
    ?>


**HTTP Operations and Callbacks**

Use a callback in the event loop to do processing on the request. In this case
we are going to use httprl_pr() as the callback function.

    <?php
    // Setup return variable.
    $x = '';
    // Setup options array.
    $options = array(
      'method' => 'HEAD',
      'callback' => array(
        array(
          'function' => 'httprl_pr',
          'return' => &$x,
        ),
      ),
    );
    // Build URL to point to front page of this server.
    $url_front = httprl_build_url_self();
    // Queue up the request.
    httprl_request($url_front, $options);
    // Execute request.
    $request = httprl_send_request();

    // Echo returned value from function callback.
    echo $x;
    ?>


Use a background callback in the event loop to do processing on the request.
In this case we are going to use httprl_pr() as the callback function. A
background callback creates a new thread to run this function in.

    <?php
    // Setup return variable.
    $x = '';
    // Setup options array.
    $options = array(
      'method' => 'HEAD',
      'background_callback' => array(
        array(
          'function' => 'httprl_pr',
          'return' => &$x,
        ),
      ),
    );
    // Build URL to point to front page of this server.
    $url_front = httprl_build_url_self();
    // Queue up the request.
    httprl_request($url_front, $options);
    // Execute request.
    $request = httprl_send_request();

    // Echo returned value from function callback.
    echo $x;
    ?>


Use a background callback in the event loop to do processing on the request.
In this case we are going to use print_r() as the callback function. A
background callback creates a new thread to run this function in. The first
argument passed in is the request object, the FALSE tells print_r to echo out
instead of returning a value.

    <?php
    // Setup return & print variable.
    $x = '';
    $y = '';
    // Setup options array.
    $options = array(
      'method' => 'HEAD',
      'background_callback' => array(
        array(
          'function' => 'print_r',
          'return' => &$x,
          'printed' => &$y,
        ),
        FALSE,
      ),
    );
    // Build URL to point to front page of this server.
    $url_front = httprl_build_url_self();
    // Queue up the request.
    httprl_request($url_front, $options);
    // Execute request.
    $request = httprl_send_request();

    // Echo what was returned and printed from function callback.
    echo $x . "<br />\n";
    echo $y;
    ?>


**More Advanced HTTP Operations**

Hit 4 different URLs, Using at least 2 that has a status code of 200 and
erroring out the others that didn't return fast. Data is truncated as well.

    <?php
    // Array of URLs to get.
    $urls = array(
      'http://google.com/',
      'http://bing.com/',
      'http://yahoo.com/',
      'http://www.duckduckgo.com/',
      'http://www.drupal.org/',
    );

    // Process list of URLs.
    $options = array(
      'alter_all_streams_function' => 'need_two_good_results',
      'callback' => array(array('function' => 'limit_data_size')),
    );
    // Queue up the requests.
    httprl_request($urls, $options);

    // Execute requests.
    $requests = httprl_send_request();

    // Print what was done.
    echo httprl_pr($requests);

    function need_two_good_results($id, &$responses) {
      static $counter = 0;
      foreach ($responses as $id => &$result) {
        // Skip if we got a 200.
        if ($result->code == 200) {
          $counter += 1;
          continue;
        }
        if ($result->status == 'Done.') {
          continue;
        }

        if ($counter >= 2) {
          // Set the code to request was aborted.
          $result->code = HTTPRL_REQUEST_ABORTED;
          $result->error = 'Software caused connection abort.';
          // Set status to done and set timeout.
          $result->status = 'Done.';
          $result->options['timeout'] -= $result->running_time;

          // Close the file pointer and remove from the stream from the array.
          fclose($result->fp);
          unset($result->fp);
        }
      }
    }

    function limit_data_size(&$result) {
      // Only use the first and last 256 characters in the data array.
      $result->data = substr($result->data, 0, 256) . "\n\n ... \n\n" . substr($result->data, strlen($result->data)-256);
    }
    ?>


Send 2 files in one field via a POST request.

    <?php
    // Send request to front page.
    $url_front = httprl_build_url_self();
    // Set options.
    $options = array(
      'method' => 'POST',
      'data' => array(
        'x' => 1,
        'y' => 2,
        'z' => 3,
        'files' => array(
          'core_js' => array(
            'misc/form.js',
            'misc/batch.js',
          ),
        ),
      ),
    );
    // Queue up the request.
    httprl_request($url_front, $options);
    // Execute request.
    $request = httprl_send_request();
    // Echo what was returned.
    echo httprl_pr($request);
    ?>


**Threading Examples**

Use 2 threads to load up 4 different nodes.

    <?php
    // List of nodes to load; 241-244.
    $nodes = array(241 => '', 242 => '', 243 => '', 244 => '');
    foreach ($nodes as $nid => &$node) {
      // Setup callback options array.
      $callback_options = array(
        array(
          'function' => 'node_load',
          'return' => &$node,
          // Setup options array.
          'options' => array(
            'domain_connections' => 2, // Only use 2 threads for this request.
          ),
        ),
        $nid,
      );
      // Queue up the request.
      httprl_queue_background_callback($callback_options);
    }
    // Execute request.
    httprl_send_request();

    // Echo what was returned.
    echo httprl_pr($nodes);
    ?>


Run a function in the background. Notice that there is no return or printed key
in the callback options.

    <?php
    // Setup callback options array; call watchdog in the background.
    $callback_options = array(
      array(
        'function' => 'watchdog',
      ),
      'httprl-test', 'background watchdog call done', array(), WATCHDOG_DEBUG,
    );
    // Queue up the request.
    httprl_queue_background_callback($callback_options);

    // Execute request.
    httprl_send_request();
    ?>


Pass by reference example. Example is D7 only; pass by reference works in
D6 & D7.

    <?php
    // Code from system_rebuild_module_data().
    $modules = _system_rebuild_module_data();
    ksort($modules);

    // Show first module before running system_get_files_database().
    echo httprl_pr(current($modules));

    $callback_options = array(
      array(
        'function' => 'system_get_files_database',
        'return' => '',
      ),
      &$modules, 'module'
    );
    httprl_queue_background_callback($callback_options);

    // Execute requests.
    httprl_send_request();

    // Show first module after running system_get_files_database().
    echo httprl_pr(current($modules));
    ?>


Get 2 results from 2 different queries at the hook_boot bootstrap level in D6.

    <?php
    // Run 2 queries and get the result.
    $x = db_result(db_query_range("SELECT filename FROM {system} ORDER BY filename ASC", 0, 1));
    $y = db_result(db_query_range("SELECT filename FROM {system} ORDER BY filename DESC", 0, 1));
    echo $x . "<br \>\n" . $y . "<br \>\n";
    unset($x, $y);


    // Run above 2 queries and get the result via a background callback.
    $args = array(
      // First query.
      array(
        'type' => 'function',
        'call' => 'db_query_range',
        'args' => array('SELECT filename FROM {system} ORDER BY filename ASC', 0, 1),
      ),
      array(
        'type' => 'function',
        'call' => 'db_result',
        'args' => array('last' => NULL),
        'return' => &$x,
      ),

      // Second Query.
      array(
        'type' => 'function',
        'call' => 'db_query_range',
        'args' => array('SELECT filename FROM {system} ORDER BY filename DESC', 0, 1),
      ),
      array(
        'type' => 'function',
        'call' => 'db_result',
        'args' => array('last' => NULL),
        'return' => &$y,
      ),
    );
    $callback_options = array(array('return' => ''), &$args);
    // Queue up the request.
    httprl_queue_background_callback($callback_options);
    // Execute request.
    httprl_send_request();

    // Echo what was returned.
    echo httprl_pr($x, $y);
    ?>


Get 2 results from 2 different queries at the hook_boot bootstrap level in D7.

    <?php
    $x = db_select('system', 's')
      ->fields('s', array('filename'))
      ->orderBy('filename', 'ASC')
      ->range(0, 1)
      ->execute()
      ->fetchField();
    $y = db_select('system', 's')
      ->fields('s', array('filename'))
      ->orderBy('filename', 'DESC')
      ->range(0, 1)
      ->execute()
      ->fetchField();
    echo $x . "<br \>\n" . $y . "<br \>\n";
    unset($x, $y);

    // Run above 2 queries and get the result via a background callback.
    $args = array(
      // First query.
      array(
        'type' => 'function',
        'call' => 'db_select',
        'args' => array('system', 's',),
      ),
      array(
        'type' => 'method',
        'call' => 'fields',
        'args' => array('s', array('filename')),
      ),
      array(
        'type' => 'method',
        'call' => 'orderBy',
        'args' => array('filename', 'ASC'),
      ),
      array(
        'type' => 'method',
        'call' => 'range',
        'args' => array(0, 1),
      ),
      array(
        'type' => 'method',
        'call' => 'execute',
        'args' => array(),
      ),
      array(
        'type' => 'method',
        'call' => 'fetchField',
        'args' => array(),
        'return' => &$x,
      ),

      // Second Query.
      array(
        'type' => 'function',
        'call' => 'db_select',
        'args' => array('system', 's',),
      ),
      array(
        'type' => 'method',
        'call' => 'fields',
        'args' => array('s', array('filename')),
      ),
      array(
        'type' => 'method',
        'call' => 'orderBy',
        'args' => array('filename', 'DESC'),
      ),
      array(
        'type' => 'method',
        'call' => 'range',
        'args' => array(0, 1),
      ),
      array(
        'type' => 'method',
        'call' => 'execute',
        'args' => array(),
      ),
      array(
        'type' => 'method',
        'call' => 'fetchField',
        'args' => array(),
        'return' => &$y,
      ),
    );
    $callback_options = array(array('return' => ''), &$args);
    // Queue up the request.
    httprl_queue_background_callback($callback_options);
    // Execute request.
    httprl_send_request();

    // Echo what was returned.
    echo httprl_pr($x, $y);
    ?>


Run a cache clear at the DRUPAL_BOOTSTRAP_FULL level as the current user in a
non blocking background request.

    <?php
    // Normal way to do this.
    drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);
    module_load_include('inc', 'system', 'system.admin');
    system_clear_cache_submit();


    // How to do it in a non blocking background request.
    $args = array(
      array(
        'type' => 'function',
        'call' => 'drupal_bootstrap',
        'args' => array(DRUPAL_BOOTSTRAP_FULL),
      ),
      array(
        'type' => 'function',
        'call' => 'module_load_include',
        'args' => array('inc', 'system', 'system.admin'),
      ),
      array(
        'type' => 'function',
        'call' => 'system_clear_cache_submit',
        'args' => array('', ''),
      ),
      array(
        'type' => 'function',
        'call' => 'watchdog',
        'args' => array('httprl-test', 'background cache clear done', array(), WATCHDOG_DEBUG),
      ),
    );

    // Pass the current session to the sub request.
    if (!empty($_COOKIE[session_name()])) {
      $options = array('headers' => array('Cookie' => session_name() . '=' . $_COOKIE[session_name()] . ';'));
    }
    else {
      $options = array();
    }
    $callback_options = array(array('options' => $options), &$args);

    // Queue up the request.
    httprl_queue_background_callback($callback_options);
    // Execute request.
    httprl_send_request();
    ?>


print 'My Text'; cut the connection by sending the data over the wire and do
processing in the background.

    <?php
    httprl_background_processing('My Text');
    // Everything after this point does not affect page load time.
    sleep(5);
    echo 'You should not see this text';
    ?>