lock-test.php

<?php

/** ======================================================================  */

// Create table if not available.
db_query("CREATE TABLE IF NOT EXISTS {lock_test} (
  id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
  random_id int,
  request_time varchar(50),
  first_request_time varchar(50)
);")->execute();

/** ======================================================================  */

// Ensure we start in both requests at same time.
do {
  $time = time();
} while ($time % 100 != 0);

print 'start time: ' . $time . PHP_EOL . PHP_EOL;

/** ======================================================================  */

$i = 0;

$connection = \Drupal::database();
$lock = new \Drupal\Core\Lock\DatabaseLockBackend($connection);

for ($i = 1; $i < 1000; $i++) {
  process($i, $lock);
  print 'Processed id: ' . $i . PHP_EOL;
}

function process($id, $lock) {
  $time = microtime(TRUE);

  $lock_key = 'lock_test_' . $id;

  // Acquire lock to ensure parallel processes are executed one by one.
  do {
    $lock_acquired = $lock->acquire($lock_key);

    // Sleep for half a second before trying again.
    if (!$lock_acquired) {
      usleep(500000);
    }
  } while (!$lock_acquired);

  $result = db_query('select id from {lock_test} where random_id = :id', [
    ':id' => $id,
  ])->fetch();

  if ($result) {
    db_update('lock_test')
      ->fields(['request_time' => $time])
      ->condition('id', $result->id)
      ->execute();
  }
  else {
    db_insert('lock_test')->fields(
      [
        'random_id' => $id,
        'request_time' => $time,
        'first_request_time' => $time,
      ]
    )->execute();
  }

  sleep(3);

  $lock->release($lock_key);
}