/**
* Remove and return items from the queue
*
* @param int $n maximum number of items to be popped
* @param int $timeout maximum time (in seconds) to wait for new items when the queue is empty
* @return PriorityItem[] array of at most $n items popped from the queue
*/
public function dequeue($n = 1, $timeout = 0)
{
//do a non-blocking dequeue, return on success
$result = $this->queue->dequeue($n, 0);
if (count($result) || $timeout < 1) {
return $result;
}
$start = microtime(true);
//if nothing popped: while timeout is not reached do the following:
while (($loopStart = microtime(true)) < $start + $timeout + 1) {
$result = $this->queue->dequeue($n, 0);
if (count($result)) {
return $result;
}
//find $t0 and $best as declared in $this->enqueue()
$first = $this->redis->zrange($this->name, 0, 0, 'WITHSCORES');
if (count($first)) {
$t0 = array_values($first)[0];
$best = array_keys($first)[0];
} else {
$t0 = $start + $timeout;
$best = 0;
}
//$x = blpop "{$this->name}:$best", $t0
//if $x: dequeue, if something is dequeued return
$timeToWait = max(1, ceil(min($timeout - $loopStart + $start, $t0 - $loopStart)));
$items = $this->redis->blpop([$this->name . ':' . $best], $timeToWait);
if (is_null($items)) {
continue;
}
$items = [$items[1]];
if ($n > 1) {
$lua = <<<LUA
local values = redis.call('lrange', KEYS[1], 0, KEYS[2] - 1)
redis.call('ltrim', KEYS[1], KEYS[2], - 1)
return values
LUA;
$remainingItems = $this->redis->eval($lua, 2, $this->name . ':' . $best, $n - 1);
$items = array_merge($items, $remainingItems);
}
$result = $this->queue->dequeue(count($items));
if (count($result)) {
return $result;
}
}
return [];
}
public function test_blocking_pop_from_empty_queue()
{
$start = time();
$this->assertEquals([], $this->queue->dequeue(1, 1));
$this->assertGreaterThan($start, time());
}
