RedisLockRegistry: Don't expire not acquired lock

Fix race condition, when methods `RedisLockRegistry#expireUnusedOlderThan` and `RedisLockRegistry#obtain` are executed successively. 

It's possible to delete the lock from `RedisLockRegistry#expireUnusedOlderThan` method, when lock is created but is not acquired (`RedisLock#getLockedAt = 0`)
It can lead to the situation, when `RedisLockRegistry#obtain` returns multiple locks with the same redis-key, which shouldn't happen at all.

* Skip locks from expiration when their `lockedAt == 0` - new, not acquired yet.

**Cherry-pick to `6.0.x` & `5.5.x`**

Author: AntonGabov

spring-integration-redis/src/main/java/org/springframework/integration/redis/util/RedisLockRegistry.java

@@ -81,6 +81,7 @@
  * @author Artem Bilan
  * @author Vedran Pavic
  * @author Unseok Kim
+ * @author Anton Gabov
  *
  * @since 4.0
  *
@@ -235,7 +236,11 @@ public void expireUnusedOlderThan(long age) {
 			this.locks.entrySet()
 					.removeIf(entry -> {
 						RedisLock lock = entry.getValue();
-						return now - lock.getLockedAt() > age && !lock.isAcquiredInThisProcess();
+						long lockedAt = lock.getLockedAt();
+						return now - lockedAt > age
+								// 'lockedAt = 0' means that the lock is still not acquired!
+								&& lockedAt > 0
+								&& !lock.isAcquiredInThisProcess();
 					});
 		}
 	}

spring-integration-redis/src/test/java/org/springframework/integration/redis/util/RedisLockRegistryTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2022 the original author or authors.
+ * Copyright 2014-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,6 +31,7 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.Lock;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
@@ -59,6 +60,7 @@
  * @author Vedran Pavic
  * @author Unseok Kim
  * @author Artem Vozhdayenko
+ * @author Anton Gabov
  *
  * @since 4.0
  *
@@ -811,6 +813,68 @@ void earlyWakeUpTest(RedisLockType testRedisLockType) throws InterruptedExceptio
 		registry3.destroy();
 	}
 
+	@ParameterizedTest
+	@EnumSource(RedisLockType.class)
+	void testTwoThreadsRemoveAndObtainSameLockSimultaneously(RedisLockType testRedisLockType) throws Exception {
+		final int TEST_CNT = 200;
+		final long EXPIRATION_TIME_MILLIS = 10000;
+		final long LOCK_WAIT_TIME_MILLIS = 500;
+		final String testKey = "testKey";
+
+		final RedisLockRegistry registry = new RedisLockRegistry(redisConnectionFactory, this.registryKey);
+		registry.setRedisLockType(testRedisLockType);
+
+		for (int i = 0; i < TEST_CNT; i++) {
+			final String lockKey = testKey + i;
+			final CountDownLatch latch = new CountDownLatch(1);
+			final AtomicReference<Lock> lock1 = new AtomicReference<>();
+			final AtomicReference<Lock> lock2 = new AtomicReference<>();
+
+			Thread thread1 = new Thread(() -> {
+				try {
+					latch.await();
+					// remove lock
+					registry.expireUnusedOlderThan(EXPIRATION_TIME_MILLIS);
+					// obtain new lock and try to acquire
+					Lock lock = registry.obtain(lockKey);
+					lock.tryLock(LOCK_WAIT_TIME_MILLIS, TimeUnit.MILLISECONDS);
+					lock.unlock();
+
+					lock1.set(lock);
+				}
+				catch (InterruptedException ignore) {
+				}
+			});
+
+			Thread thread2 = new Thread(() -> {
+				try {
+					latch.await();
+					// remove lock
+					registry.expireUnusedOlderThan(EXPIRATION_TIME_MILLIS);
+					// obtain new lock and try to acquire
+					Lock lock = registry.obtain(lockKey);
+					lock.tryLock(LOCK_WAIT_TIME_MILLIS, TimeUnit.MILLISECONDS);
+					lock.unlock();
+
+					lock2.set(lock);
+				}
+				catch (InterruptedException ignore) {
+				}
+			});
+
+			thread1.start();
+			thread2.start();
+			latch.countDown();
+			thread1.join();
+			thread2.join();
+
+			// locks must be the same!
+			assertThat(lock1.get()).isEqualTo(lock2.get());
+		}
+
+		registry.destroy();
+	}
+
 	private Long getExpire(RedisLockRegistry registry, String lockKey) {
 		StringRedisTemplate template = createTemplate();
 		String registryKey = TestUtils.getPropertyValue(registry, "registryKey", String.class);