hystrix 的相关代码学习2

dev-protocol-springcloud/SpringCloud项目介绍.md

@@ -10,7 +10,7 @@
 - 分布式链路、日志追踪 - (Sleuth + Zipkin)
   - [dev-protocol-springcloud-sleuth-zipkin](dev-protocol-springcloud-sleuth-zipkin)
 - 微服务容错 - (SpringCloud Netflix Hystrix)
-  - todo
+  - [dev-protocol-springcloud-hystrix](dev-protocol-springcloud-hystrix)
 - 消息驱动微服务 - (SpringCloud Stream)
   - todo
 - 分布式事务 - (SpringCloud Alibaba Seata)

dev-protocol-springcloud/dev-protocol-springcloud-hystrix/NetflixHystrix.md

@@ -27,7 +27,7 @@
 - [NacosClientHystrixCommand.java] - [NacosClientHystrixObservableCommand.java]
 
 ### 编程方式开启 Hystrix 请求缓存
-
+- 先编写过滤器 [HystrixRequestContextServletFilter.java]
 
 ### 注解方式开启 Hystrix 请求缓存
 

dev-protocol-springcloud/dev-protocol-springcloud-hystrix/src/main/java/org/example/controller/HystrixController.java

@@ -2,11 +2,11 @@ package org.example.controller;
 
 import com.alibaba.fastjson.JSON;
 import lombok.extern.slf4j.Slf4j;
+import org.example.hystrix.CacheHystrixCommand;
 import org.example.hystrix.NacosClientHystrixCommand;
 import org.example.hystrix.NacosClientHystrixObservableCommand;
 import org.example.hystrix.UseHystrixCommandAnnotation;
 import org.example.service.NacosClientService4HystrixDemo;
-import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.cloud.client.ServiceInstance;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -129,4 +129,39 @@ public class HystrixController {
                 JSON.toJSONString(result), Thread.currentThread().getName());
         return result.get(0); // 取一个返回
     }
+
+    @GetMapping("/cache-hystrix-command")
+    public void cacheHystrixCommand(@RequestParam String serviceId) {
+
+        // 使用缓存 Command, 连续发起两次请求
+        CacheHystrixCommand command1 = new CacheHystrixCommand(
+                nacosClientService4HystrixDemo, serviceId
+        );
+        CacheHystrixCommand command2 = new CacheHystrixCommand(
+                nacosClientService4HystrixDemo, serviceId
+        );
+
+        List<ServiceInstance> result01 = command1.execute();
+        List<ServiceInstance> result02 = command2.execute();
+        // 看是否只执行了一次 run 方法
+        log.info("result01, result02: [{}], [{}]",
+                JSON.toJSONString(result01), JSON.toJSONString(result02));
+
+        // 清除缓存
+        CacheHystrixCommand.flushRequestCache(serviceId);
+
+        // 使用缓存 Command, 发起两次请求
+        CacheHystrixCommand command3 = new CacheHystrixCommand(
+                nacosClientService4HystrixDemo, serviceId
+        );
+        CacheHystrixCommand command4 = new CacheHystrixCommand(
+                nacosClientService4HystrixDemo, serviceId
+        );
+
+        List<ServiceInstance> result03 = command3.execute();
+        List<ServiceInstance> result04 = command4.execute();
+        // 看是否成功清除缓存
+        log.info("result03, result04: [{}], [{}]",
+                JSON.toJSONString(result03), JSON.toJSONString(result04));
+    }
 }

dev-protocol-springcloud/dev-protocol-springcloud-hystrix/src/main/java/org/example/filter/HystrixRequestContextServletFilter.java

@@ -49,6 +49,7 @@ public class HystrixRequestContextServletFilter implements Filter {
 
     /**
      * <h2>配置 Hystrix 的并发策略</h2>
+     * 重写的原因, 是官方不建议引用 Sleuth, 但是我们重写了下述代码
      * */
     public void hystrixConcurrencyStrategyConfig() {
 
@@ -59,7 +60,7 @@ public class HystrixRequestContextServletFilter implements Filter {
             HystrixConcurrencyStrategy strategy =
                     HystrixPlugins.getInstance().getConcurrencyStrategy();
             if (strategy instanceof HystrixConcurrencyStrategyDefault) {
-                // 如果已经就是我们想要配置的
+                // 如果已经就是我们想要配置的, 直接返回
                 return;
             }
 
@@ -83,6 +84,7 @@ public class HystrixRequestContextServletFilter implements Filter {
 
             log.info("config hystrix concurrency strategy success");
         } catch (Exception ex) {
+            // 注册失败的可能性很小, 所以用大 catch
             log.error("Failed to register Hystrix Concurrency Strategy: [{}]",
                     ex.getMessage(), ex);
         }

dev-protocol-springcloud/dev-protocol-springcloud-hystrix/src/main/java/org/example/hystrix/CacheHystrixCommand.java

@@ -0,0 +1,75 @@
+package org.example.hystrix;
+
+import com.netflix.hystrix.HystrixCommand;
+import com.netflix.hystrix.HystrixCommandGroupKey;
+import com.netflix.hystrix.HystrixCommandKey;
+import com.netflix.hystrix.HystrixRequestCache;
+import com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategyDefault;
+import java.util.List;
+import lombok.extern.slf4j.Slf4j;
+import org.example.service.NacosClientService4HystrixDemo;
+import org.springframework.cloud.client.ServiceInstance;
+
+import java.util.Collections;
+
+/**
+ * <h1>带有缓存功能的 Hystrix</h1>
+ * */
+@Slf4j
+public class CacheHystrixCommand extends HystrixCommand<List<ServiceInstance>> {
+
+    /** 需要保护的服务 */
+    private final NacosClientService4HystrixDemo nacosClientService;
+
+    /** 方法需要传递的参数 */
+    private final String serviceId;
+
+    private static final HystrixCommandKey CACHED_KEY =
+            HystrixCommandKey.Factory.asKey("CacheHystrixCommand");
+
+    public CacheHystrixCommand(NacosClientService4HystrixDemo nacosClientService, String serviceId) {
+
+        super(
+                HystrixCommand.Setter
+                        .withGroupKey(HystrixCommandGroupKey
+                                .Factory.asKey("CacheHystrixCommandGroup"))
+                        .andCommandKey(CACHED_KEY)
+        );
+
+        this.nacosClientService = nacosClientService;
+        this.serviceId = serviceId;
+    }
+
+    @Override
+    protected List<ServiceInstance> run() throws Exception {
+
+        log.info("CacheHystrixCommand In Hystrix Command to get service instance:" +
+                " [{}], [{}]", this.serviceId, Thread.currentThread().getName());
+        return this.nacosClientService.getNacosClientInfo(this.serviceId);
+    }
+
+    @Override
+    protected String getCacheKey() {
+        // fixme 可以进行自定义, 只要保证唯一的请求返回唯一的值即可
+        return serviceId;
+    }
+
+    @Override
+    protected List<ServiceInstance> getFallback() {
+        // todo 这里可以自己添加一些 warning 日志来进行表示
+        return Collections.emptyList();
+    }
+
+    /**
+     * <h2>根据缓存 key 清理在一次 Hystrix 请求上下文中的缓存</h2>
+     * */
+    public static void flushRequestCache(String serviceId) {
+
+        HystrixRequestCache.getInstance(
+                CACHED_KEY,
+                HystrixConcurrencyStrategyDefault.getInstance()
+        ).clear(serviceId);
+        log.info("flush request cache in hystrix command: [{}], [{}]",
+                serviceId, Thread.currentThread().getName());
+    }
+}