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<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* Task for updating RSS feeds for rss client block
*
* @package block_rss_client
* @author Farhan Karmali <farhan6318@gmail.com>
* @copyright Farhan Karmali 2018
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
namespace block_rss_client\task;
defined('MOODLE_INTERNAL') || die();
/**
* Task for updating RSS feeds for rss client block
*
* @package block_rss_client
* @author Farhan Karmali <farhan6318@gmail.com>
* @copyright Farhan Karmali 2018
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class refreshfeeds extends \core\task\scheduled_task {
/** The maximum time in seconds that cron will wait between attempts to retry failing RSS feeds. */
const CLIENT_MAX_SKIPTIME = HOURSECS * 12;
/**
* Name for this task.
*
* @return string
*/
public function get_name() {
return get_string('refreshfeedstask', 'block_rss_client');
}
/**
* This task goes through all the feeds. If the feed has a skipuntil value
* that is less than the current time cron will attempt to retrieve it
* with the cache duration set to 0 in order to force the retrieval of
* the item and refresh the cache.
*
* If a feed fails then the skipuntil time of that feed is set to be
* later than the next expected task time. The amount of time will
* increase each time the fetch fails until the maximum is reached.
*
* If a feed that has been failing is successfully retrieved it will
* go back to being handled as though it had never failed.
*
* Task should therefore process requests for permanently broken RSS
* feeds infrequently, and temporarily unavailable feeds will be tried
* less often until they become available again.
*/
public function execute() {
global $CFG, $DB;
require_once("{$CFG->libdir}/simplepie/moodle_simplepie.php");
// We are going to measure execution times.
$starttime = microtime();
$starttimesec = time();
// Fetch all site feeds.
$rs = $DB->get_recordset('block_rss_client');
$counter = 0;
mtrace('');
foreach ($rs as $rec) {
mtrace(' ' . $rec->url . ' ', '');
// Skip feed if it failed recently.
if ($starttimesec < $rec->skipuntil) {
mtrace('skipping until ' . userdate($rec->skipuntil));
continue;
}
$feed = $this->fetch_feed($rec->url);
if ($feed->error()) {
// Skip this feed (for an ever-increasing time if it keeps failing).
$rec->skiptime = $this->calculate_skiptime($rec->skiptime);
$rec->skipuntil = time() + $rec->skiptime;
$DB->update_record('block_rss_client', $rec);
mtrace("Error: could not load/find the RSS feed - skipping for {$rec->skiptime} seconds.");
} else {
mtrace ('ok');
// It worked this time, so reset the skiptime.
if ($rec->skiptime > 0) {
$rec->skiptime = 0;
$rec->skipuntil = 0;
$DB->update_record('block_rss_client', $rec);
}
// Only increase the counter when a feed is sucesfully refreshed.
$counter ++;
}
}
$rs->close();
// Show times.
mtrace($counter . ' feeds refreshed (took ' . microtime_diff($starttime, microtime()) . ' seconds)');
}
/**
* Fetch a feed for the specified URL.
*
* @param string $url The URL to fetch
* @return \moodle_simplepie
*/
protected function fetch_feed(string $url) : \moodle_simplepie {
// Fetch the rss feed, using standard simplepie caching so feeds will be renewed only if cache has expired.
\core_php_time_limit::raise(60);
$feed = new \moodle_simplepie();
// Set timeout for longer than normal to be agressive at fetching feeds if possible..
$feed->set_timeout(40);
$feed->set_cache_duration(0);
$feed->set_feed_url($url);
$feed->init();
return $feed;
}
/**
* Calculates a new skip time for a record based on the current skip time.
*
* @param int $currentskip The current skip time of a record.
* @return int The newly calculated skip time.
*/
protected function calculate_skiptime(int $currentskip) : int {
// If the feed has never failed, then the initial skiptime will be 0. We use a default of 5 minutes in this case.
// If the feed has previously failed then we double that time.
$newskiptime = max(MINSECS * 5, ($currentskip * 2));
// Max out at the CLIENT_MAX_SKIPTIME.
return min($newskiptime, self::CLIENT_MAX_SKIPTIME);
}
}