Spring Cloud Gateway MVC 使用SseEmitter时存在SSE连接泄漏问题

阿华AIGC实验室

2026-4-1

我最近在使用Spring Cloud Gateway MVC路由到内部API时遇到了一个头疼的问题：当后端API用SseEmitter实现Server-Sent-Events（SSE）长连接时，网关无法正确感知客户端断开的信号，导致后端的SseEmitter长连接和线程一直被占用，形成连接泄漏。而换成响应式的Spring Cloud Gateway就完全正常，这就很让人困惑了。

问题复现场景

我写了一个极简的复现示例，后端API的配置和核心代码如下：

后端API基础配置

server.port: 8781
spring.application.name: api

后端SSE接口实现

import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
import java.util.UUID;
import java.time.Instant;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import com.fasterxml.jackson.annotation.JsonProperty;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class SseController {
    private static final Logger log = LoggerFactory.getLogger(SseController.class);

    public record EventDetails(
        @JsonProperty("eventId") UUID id,
        @JsonProperty("timestamp") Instant time,
        @JsonProperty("counter") int counter
    ) { }

    @GetMapping("/stream-sse-mvc")
    public SseEmitter streamSseMvc() {
        // 创建无超时的SseEmitter
        SseEmitter emitter = new SseEmitter(-1L);
        ExecutorService sseMvcExecutor = Executors.newSingleThreadExecutor();

        // 注册生命周期回调，用于监控连接状态
        emitter.onCompletion(() -> {
            log.info("Emitter has been closed");
            sseMvcExecutor.shutdownNow();
        });
        emitter.onTimeout(() -> {
            log.info("Emitter has timed out");
            emitter.complete();
        });
        emitter.onError(t -> {
            log.error("Emitter completed with error", t);
            emitter.completeWithError(t);
        });

        // 启动线程每秒发送一条SSE事件
        sseMvcExecutor.submit(() -> {
            try {
                for (int i = 0; true; i++) {
                    final UUID id = UUID.randomUUID();
                    SseEmitter.SseEventBuilder event = SseEmitter.event()
                            .data(new EventDetails(id, Instant.now(), i + 1))
                            .id(id.toString())
                            .name("sse event - mvc");

                    log.info("Sending event. [counter={}]", i);
                    emitter.send(event);
                    Thread.sleep(1000);
                }
            } catch (InterruptedException e) {
                log.info("Sending thread interrupted");
                Thread.currentThread().interrupt();
            } catch (Exception e) {
                log.error("Failed to send SSE event", e);
                emitter.completeWithError(e);
            }
        });

        return emitter;
    }
}

这个接口的逻辑很简单：创建一个无超时的SseEmitter，启动单独线程每秒向客户端发送一条事件，循环不会主动终止，全靠客户端断开时触发的回调来清理资源。

现象对比

直接调用后端接口：正常工作

当我直接用HTTP客户端（比如curl、Postman）调用这个SSE接口，然后主动断开连接时，后端的SseEmitter会立刻感知到：

触发onError回调，打印错误日志
触发onCompletion回调，关闭线程池
发送线程会因为emitter.send()抛出异常而终止

对应的日志如下：

2025-11-25T17:19:41.671+01:00 INFO 168228 --- [api] [pool-2-thread-1] c.rbellini.api.controller.SseController : Sending event. [counter=0]
2025-11-25T17:19:42.740+01:00 INFO 168228 --- [api] [pool-2-thread-1] c.rbellini.api.controller.SseController : Sending event. [counter=1]
...
2025-11-25T17:19:52.762+01:00 INFO 168228 --- [api] [pool-2-thread-1] c.rbellini.api.controller.SseController : Sending event. [counter=11]
2025-11-25T17:19:52.765+01:00 ERROR 168228 --- [api] [nio-8781-exec-1] c.rbellini.api.controller.SseController : Emitter completed with error
org.springframework.web.context.request.async.AsyncRequestNotUsableException: Servlet container error notification for disconnected client
...
2025-11-25T17:19:52.766+01:00 INFO 168228 --- [api] [pool-2-thread-1] c.rbellini.api.controller.SseController : Emitter has been closed