+
+ /**
+ * @param mixed $transports name of a single queue or array of queues to pull from
+ * If not specified, checks all queues in the system.
+ */
+ static function top($transports=null) {
+
+ $qi = new Queue_item();
+ if ($transports) {
+ if (is_array($transports)) {
+ // @fixme use safer escaping
+ $list = implode("','", array_map(array($qi, 'escape'), $transports));
+ $qi->whereAdd("transport in ('$list')");
+ } else {
+ $qi->transport = $transports;
+ }
+ }
+ $qi->orderBy('created');
+ $qi->whereAdd('claimed is null');
+
+ $qi->limit(1);
+
+ $cnt = $qi->find(true);
+
+ if ($cnt) {
+ # XXX: potential race condition
+ # can we force it to only update if claimed is still null
+ # (or old)?
+ common_log(LOG_INFO, 'claiming queue item id = ' . $qi->id .
+ ' for transport ' . $qi->transport);
+ $orig = clone($qi);
+ $qi->claimed = common_sql_now();
+ $result = $qi->update($orig);
+ if ($result) {
+ common_log(LOG_INFO, 'claim succeeded.');
+ return $qi;
+ } else {
+ common_log(LOG_INFO, 'claim failed.');
+ }
+ }
+ $qi = null;
+ return null;
+ }
+
+ /**
+ * Release a claimed item.
+ */
+ function releaseCLaim()
+ {
+ // DB_DataObject doesn't let us save nulls right now
+ $sql = sprintf("UPDATE queue_item SET claimed=NULL WHERE id=%d", $this->id);
+ $this->query($sql);
+
+ $this->claimed = null;
+ $this->encache();
+ }