Java Spring Boot: Handling Concurrent Requests with Redis Caching for Rate Limiting
I'm optimizing some code but I keep running into I am currently building a REST API using Spring Boot and I want to implement rate limiting to prevent abuse... I decided to use Redis for caching to store user request counts. However, I'm working with issues with handling concurrent requests properly, which leads to inaccurate counts and sometimes even exceeds the defined limits. Here's a simplified version of what I've implemented so far: ```java @RestController public class RateLimitController { private final StringRedisTemplate redisTemplate; public RateLimitController(StringRedisTemplate redisTemplate) { this.redisTemplate = redisTemplate; } @GetMapping("/api/resource") public ResponseEntity<String> getResource(HttpServletRequest request) { String userId = request.getHeader("X-User-Id"); String key = "rate_limit:" + userId; Long requests = redisTemplate.opsForValue().increment(key); if (requests == 1) { redisTemplate.expire(key, 1, TimeUnit.MINUTES); } if (requests != null && requests > 10) { return ResponseEntity.status(HttpStatus.TOO_MANY_REQUESTS) .body("Rate limit exceeded"); } return ResponseEntity.ok("Resource accessed"); } } ``` I've noticed that when multiple requests come in at the same time, the `increment` method does not accurately reflect the number of requests due to race conditions. Sometimes users get a 'Rate limit exceeded' message even though they haven't reached the limit. I've tried using `RedisTemplate` with atomic operations, but it seems like the question continues, especially under heavy load. I've also considered implementing a locking mechanism using Redis, but I'm unsure how to do that effectively without introducing important latency. What would be the best approach to ensure accurate rate limiting with Redis in this scenario? Any suggestions on patterns or libraries that can guide to manage concurrent requests more effectively would be greatly appreciated! Has anyone else encountered this? The project is a mobile app built with Java.