Improve distributed locking

src/Mutex/DistributedMutex.php

@@ -52,9 +52,10 @@ protected function acquireWithToken(string $key, float $expireTimeout)
 
  // 2.
  $acquiredIndexes = [];
+ $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;
@@ -68,6 +69,14 @@ protected function acquireWithToken(string $key, float $expireTimeout)
 
  ++$errored;
  }
+
+ if (end($acquiredIndexes) !== $index) {
+ ++$notAcquired;
+ }
+
+ if (!$this->isCountMajority(count($this->mutexes) - $notAcquired)) {
+ break;
+ }
  }
 
  // 3.
@@ -129,6 +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;
- $mutex->expects(self::exactly($count))
+ $mutex->expects(self::atMost((int) floor($count / 2) + $count - $available))
  ->method('acquireMutex')
  ->willReturnCallback(static function () use (&$i, $available) {
  if ($i++ < $available) {
@@ -307,6 +307,9 @@ public static function provideMinorityCases(): iterable
  yield [4, 0];
  yield [4, 1];
  yield [4, 2];
+ yield [5, 2];
+ yield [6, 2];
+ yield [6, 3];
  }
 
  /**
@@ -321,6 +324,7 @@ public static function provideMajorityCases(): iterable
  yield [3, 2];
  yield [3, 3];
  yield [4, 3];
+ yield [5, 3];
  }
 
  public function testAcquireMutexLogger(): void
@@ -329,12 +333,12 @@ public function testAcquireMutexLogger(): void
  $logger = $this->createMock(LoggerInterface::class);
  $mutex->setLogger($logger);
 
- $mutex->expects(self::exactly(3))
+ $mutex->expects(self::exactly(2))
  ->method('acquireMutex')
  ->with(self::isInstanceOf(AbstractSpinlockMutex::class), 'distributed', 1.0, \INF)
  ->willThrowException($this->createMock(/* PredisException::class */ LockAcquireException::class));
 
- $logger->expects(self::exactly(3))
+ $logger->expects(self::exactly(2))
  ->method('warning')
  ->with('Could not set {key} = {token} at server #{index}', self::anything());