Atomic can be used for interprocess variable synchronization.

The integer variable defined with Atomic allows multiple processes access and update it. It is implemented based on CPU atomic instructions. You can use it to implement a high performance counter service with multiple Worker.

The underlayer implemention is CAS: Compare-and-swap (CAS) is an atomic instruction used in multithreading to achieve synchronization. It compares the contents of a memory location with a given value and, only if they are the same, modifies the contents of that memory location to a new given value.


  • Swoole\Atomic->__construct
  • Swoole\Atomic\add
  • Swoole\Atomic\sub
  • Swoole\Atomic\get
  • Swoole\Atomic\set
  • Swoole\Atomic\wait
  • Swoole\Atomic\wakeup
  • Swoole\Atomic\cmpset
  • Swoole\Atomic\Long->__construct
  • Swoole\Atomic\Long\add
  • Swoole\Atomic\Long\sub
  • Swoole\Atomic\Long\get
  • Swoole\Atomic\Long\set
  • Swoole\Atomic\Long\cmpset


    • The Atomic variables have to created before Swoole\Server->start. Then you can access and update it within Worker.
    • You should not define or create a new Atomic within server callbacks like request, receive etc.
    • The integer type is a Int32, but your can use new Swoole\Atomic\Long to create Int64 type.
    • wait and wakeup method is not supported for Swoole\Atomic\Long


    $counter = new Swoole\Atomic(123);
    echo $counter->add(12)."\n";
    echo $counter->sub(11)."\n";
    echo $counter->cmpset(122, 999)."\n";
    echo $counter->cmpset(124, 999)."\n";
    echo $counter->get()."\n";
    $counter = new Swoole\Atomic();
    $server = new Swoole\Server('', '9501');
        'worker_num' => 1,
        'log_file' => '/dev/null'
    $server->on("start", function ($server) use ($counter) {
        if ($counter->add() == 10) {
    $server->on("receive", function () use ($counter) {