RedisCache.java get(...) method will return null in some cases [DATAREDIS-777]

Sophist Wu opened DATAREDIS-777 and commented

org.springframework.data.redis.cache.RedisCache#get(org.springframework.data.redis.cache.RedisCacheKey)

public RedisCacheElement get(final RedisCacheKey cacheKey) {

		Assert.notNull(cacheKey, "CacheKey must not be null!");

		Boolean exists = (Boolean) redisOperations.execute(new RedisCallback<Boolean>() {

			@Override
			public Boolean doInRedis(RedisConnection connection) throws DataAccessException {
				return connection.exists(cacheKey.getKeyBytes());
			}
		});

		if (!exists.booleanValue()) {
			return null;
		}
                // The problem here is : What if the key expires, at this moments? The below return clause , will lookup in redis server for the key again, which would return null in the end.
		return new RedisCacheElement(cacheKey, fromStoreValue(lookup(cacheKey)));
	}

This problem doesn’t exist in 2.x and 1.7.x , but we don’t want upgrade to 2.x right now

---

Affects: 1.8.10 (Ingalls SR10)

Issue Links:

• DATAREDIS-673 RedisCache.get(…) returns false positive cache hit when key is deleted in-flight (“duplicates”)

[spring-projects-issues]

Sophist Wu commented

I see what you changed in this version : to check from redis server , see if the corresponding value exist at redis server, if not , null will be returned (in 1.8.10 will return RedisCacheElement(cacheKey, fromStoreValue(null)).

public RedisCacheElement get(final RedisCacheKey cacheKey) {

		Assert.notNull(cacheKey, "CacheKey must not be null!");

		Boolean exists = (Boolean) redisOperations.execute(new RedisCallback<Boolean>() {

			@Override
			public Boolean doInRedis(RedisConnection connection) throws DataAccessException {
				return connection.exists(cacheKey.getKeyBytes());
			}
		});

		if (!exists) {
			return null;
		}

		byte[] bytes = doLookup(cacheKey);

		// safeguard if key gets deleted between EXISTS and GET calls.
		if (bytes == null) {
			return null;
		}

		return new RedisCacheElement(cacheKey, fromStoreValue(deserialize(bytes)));
	}

Okay, many thanks, the logic seems correct, I will try if that works!

[spring-projects-issues]

Sophist Wu commented

Thank you, Mark, It works now with 1.8.11 ! We can close this jira now