How to implement rate limiting in a Spring Boot REST API without blocking requests?
I'm reviewing some code and Can someone help me understand This might be a silly question, but I've looked through the documentation and I'm still confused about I'm currently developing a REST API using Spring Boot (version 2.5.0) that needs to handle rate limiting to prevent abuse... My goal is to limit API requests to 100 per minute per user. However, I'm facing an issue where my current implementation blocks requests rather than gracefully returning an error response when the limit is exceeded. I've tried using the `Bucket4j` library to implement this functionality. Here's a simplified version of my setup: ```java import net.jodah.expiringmap.ExpiringMap; import net.jodah.expiringmap.ExpirationListener; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestHeader; import org.springframework.web.bind.annotation.RestController; import java.util.concurrent.TimeUnit; @RestController public class RateLimitController { private final ExpiringMap<String, Integer> requestCounter = ExpiringMap.builder() .expirationListener((key, value) -> requestCounter.remove(key)) .variableExpiration() .build(); @GetMapping("/api/resource") public String getResource(@RequestHeader("X-USER-ID") String userId) { int count = requestCounter.getOrDefault(userId, 0); if (count >= 100) { return "Error: Rate limit exceeded"; // This is where I want to stop processing. } requestCounter.put(userId, count + 1, 1, TimeUnit.MINUTES); return "Resource data"; } } ``` With this approach, it seems to correctly track the number of requests per user, but I noticed that when the limit is exceeded, it still processes the request before returning the error message, which is not what I want. I want to prevent any further processing of the request once the limit is reached. I've also considered using filters to intercept the request earlier in the chain, but I am unsure how to implement that effectively within the Spring Boot framework. Any suggestions on how I can modify my approach to achieve a non-blocking rate limiting implementation? Additionally, if there are better libraries or patterns for handling rate limiting in this context, I'd love to hear about those as well. My development environment is macOS. Thanks in advance! For context: I'm using Java on Linux. I'd really appreciate any guidance on this. This issue appeared after updating to Java 3.9. Any ideas what could be causing this?