fix issue 2485 which occur oom when using async servlet request.

sentinel-adapter/sentinel-spring-webmvc-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/spring/webmvc/AbstractSentinelInterceptor.java

@@ -26,9 +26,11 @@
 import com.alibaba.csp.sentinel.slots.block.BlockException;
 import com.alibaba.csp.sentinel.util.AssertUtil;
 import com.alibaba.csp.sentinel.util.StringUtil;
+
 import org.springframework.web.context.request.RequestContextHolder;
 import org.springframework.web.context.request.ServletRequestAttributes;
-import org.springframework.web.servlet.HandlerInterceptor;
+import org.springframework.web.method.HandlerMethod;
+import org.springframework.web.servlet.AsyncHandlerInterceptor;
 import org.springframework.web.servlet.ModelAndView;
 
 import javax.servlet.http.HttpServletRequest;
@@ -54,7 +56,7 @@
  * @author kaizi2009
  * @since 1.7.1
  */
-public abstract class AbstractSentinelInterceptor implements HandlerInterceptor {
+public abstract class AbstractSentinelInterceptor implements AsyncHandlerInterceptor {
 
     public static final String SENTINEL_SPRING_WEB_CONTEXT_NAME = "sentinel_spring_web_context";
     private static final String EMPTY_ORIGIN = "";
@@ -135,21 +137,43 @@ protected String getContextName(HttpServletRequest request) {
         return SENTINEL_SPRING_WEB_CONTEXT_NAME;
     }
 
+
+    /**
+     * When a handler starts an asynchronous request, the DispatcherServlet exits without invoking postHandle and afterCompletion
+     * Called instead of postHandle and afterCompletion to exit the context and clean thread-local variables when the handler is being executed concurrently.
+     * @param request the current request
+     * @param response the current response
+     * @param handler the handler (or {@link HandlerMethod}) that started async
+     * execution, for type and/or instance examination
+     */
+    @Override
+    public void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response,
+                                        Object handler) throws Exception {
+        exitContext(request);
+    }
     @Override
     public void afterCompletion(HttpServletRequest request, HttpServletResponse response,
                                 Object handler, Exception ex) throws Exception {
+        exitContext(request, ex);
+    }
+
+    private void exitContext(HttpServletRequest request) {
+        exitContext(request, null);
+    }
+
+    private void exitContext(HttpServletRequest request, Exception ex) {
         if (increaseReference(request, this.baseWebMvcConfig.getRequestRefName(), -1) != 0) {
             return;
         }
-        
+
         Entry entry = getEntryInRequest(request, baseWebMvcConfig.getRequestAttributeName());
         if (entry == null) {
             // should not happen
             RecordLog.warn("[{}] No entry found in request, key: {}",
                     getClass().getSimpleName(), baseWebMvcConfig.getRequestAttributeName());
             return;
         }
-        
+
         traceExceptionAndExit(entry, ex);
         removeEntryInRequest(request);
         ContextUtil.exit();

sentinel-adapter/sentinel-spring-webmvc-adapter/src/test/java/com/alibaba/csp/sentinel/adapter/spring/webmvc/SentinelSpringMvcIntegrationTest.java

@@ -17,10 +17,12 @@
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
 
+import com.alibaba.csp.sentinel.context.ContextUtil;
 import com.alibaba.csp.sentinel.node.ClusterNode;
 import com.alibaba.csp.sentinel.slots.block.RuleConstant;
 import com.alibaba.csp.sentinel.slots.block.degrade.DegradeRule;
@@ -66,6 +68,18 @@ public void testBase() throws Exception {
         assertEquals(1, cn.passQps(), 0.01);
     }
 
+    @Test
+    public void testAsync() throws Exception {
+        String url = "/async";
+        this.mvc.perform(get(url))
+                .andExpect(status().isOk());
+
+        ClusterNode cn = ClusterBuilderSlot.getClusterNode(url);
+        assertNotNull(cn);
+        assertEquals(1, cn.passQps(), 0.01);
+        assertNull(ContextUtil.getContext());
+    }
+
     @Test
     public void testOriginParser() throws Exception {
         String springMvcPathVariableUrl = "/foo/{id}";

sentinel-adapter/sentinel-spring-webmvc-adapter/src/test/java/com/alibaba/csp/sentinel/adapter/spring/webmvc/controller/TestController.java

@@ -19,7 +19,9 @@
 import com.alibaba.csp.sentinel.adapter.spring.webmvc.exception.BizException;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.ResponseBody;
 import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.context.request.async.DeferredResult;
 
 /**
  * @author kaizi2009
@@ -58,4 +60,16 @@ public String apiExclude(@PathVariable("id") Long id) {
         return "Exclude " + id;
     }
 
+    @GetMapping("/async")
+    @ResponseBody
+    public DeferredResult<String> distribute() throws Exception{
+        DeferredResult<String> result = new DeferredResult<>();
+
+        Thread thread = new Thread(() -> result.setResult("async result."));
+        thread.start();
+
+        Thread.yield();
+        return result;
+    }
+
 }

sentinel-demo/sentinel-demo-spring-webmvc/src/main/java/com/alibaba/csp/sentinel/demo/spring/webmvc/controller/WebMvcTestController.java

@@ -17,10 +17,12 @@
 
 import java.util.Random;
 import java.util.concurrent.TimeUnit;
+
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.ResponseBody;
+import org.springframework.web.context.request.async.DeferredResult;
 import org.springframework.web.servlet.ModelAndView;
 
 /**
@@ -65,6 +67,17 @@ public ModelAndView apiForward() {
         return mav;
     }
 
+    @GetMapping("/async")
+    @ResponseBody
+    public DeferredResult<String> distribute() throws Exception{
+//        return new DeferredResult<String>(5000L, (Supplier<String>) () -> {doBusiness(); return "err";});
+        DeferredResult<String> result = new DeferredResult<>(4000L);
+
+        Thread thread = new Thread(() -> result.setResult("async result"));
+        thread.start();
+
+        return result;
+    }
     private void doBusiness() {
         Random random = new Random(1);
         try {