acquire mutexes in random order

Author: mvorisek

src/Mutex/DistributedMutex.php

@@ -55,7 +55,7 @@ protected function acquireWithToken(string $key, float $expireTimeout)
         $notAcquired = 0;
         $errored = 0;
         $exception = null;
-        foreach ($this->mutexes as $index => $mutex) {
+        foreach ($this->getMutexesInRandomOrder() as $index => $mutex) {
             try {
                 if ($this->acquireMutex($mutex, $key, $acquireTimeout - (microtime(true) - $startTs), $expireTimeout)) {
                     $acquiredIndexes[] = $index;
@@ -138,6 +138,22 @@ protected function releaseWithToken(string $key, string $token): bool
         }
     }
 
+    /**
+     * @return array<int, AbstractSpinlockMutex>
+     */
+    private function getMutexesInRandomOrder(): array
+    {
+        $indexes = array_keys($this->mutexes);
+        shuffle($indexes);
+
+        $res = [];
+        foreach ($indexes as $index) {
+            $res[$index] = $this->mutexes[$index];
+        }
+
+        return $res;
+    }
+
     /**
      * @return bool True if the count is the majority
      */

tests/Mutex/DistributedMutexTest.php

@@ -93,7 +93,7 @@ public function testTooFewServerToAcquire(int $count, int $available): void
         $mutex = $this->createDistributedMutexMock($count);
 
         $i = 0;
-        $mutex->expects(self::atMost((int) floor($count / 2) +  $count - $available))
+        $mutex->expects(self::atMost((int) floor($count / 2) + $count - $available))
             ->method('acquireMutex')
             ->willReturnCallback(static function () use (&$i, $available) {
                 if ($i++ < $available) {