详解spring cloud hystrix缓存功能的使用
hystrix缓存的作用是
- 1.减少重复的请求数,降低依赖服务的返回数据始终保持一致。
- 2.==在同一个用户请求的上下文中,相同依赖服务的返回数据始终保持一致==。
- 3.请求缓存在run()和construct()执行之前生效,所以可以有效减少不必要的线程开销。
1 通过HystrixCommand类实现
1.1 开启缓存功能
继承HystrixCommand或HystrixObservableCommand,覆盖getCacheKey()方法,指定缓存的key,开启缓存配置。
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 com.szss.demo.orders.vo.UserVO; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.web.client.RestTemplate; public class UserCacheCommand extends HystrixCommand<UserVO> { private static final Logger LOGGER = LoggerFactory.getLogger(UserCacheCommand.class); private static final HystrixCommandKey GETTER_KEY= HystrixCommandKey.Factory.asKey("CommandKey"); private RestTemplate restTemplate; private String username; public UserCacheCommand(RestTemplate restTemplate, String username) { super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("userCacheCommand")).andCommandKey(GETTER_KEY)); this.restTemplate = restTemplate; this.username = username; } @Override protected UserVO run() throws Exception { LOGGER.info("thread:" + Thread.currentThread().getName()); return restTemplate.getForObject("http://users-service/user/name/{username}", UserVO.class, username); } @Override protected UserVO getFallback() { UserVO user = new UserVO(); user.setId(-1L); user.setUsername("调用失败"); return user; } @Override protected String getCacheKey() { return username; } public static void flushCache(String username){ HystrixRequestCache.getInstance(GETTER_KEY, HystrixConcurrencyStrategyDefault.getInstance()).clear(username); } }
1.2 配置HystrixRequestContextServletFilter
通过servlet的Filter配置hystrix的上下文。
import com.netflix.hystrix.strategy.concurrency.HystrixRequestContext; import javax.servlet.*; import javax.servlet.annotation.WebFilter; import java.io.IOException; @WebFilter(filterName = "hystrixRequestContextServletFilter",urlPatterns = "/*",asyncSupported = true) public class HystrixRequestContextServletFilter implements Filter { public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { HystrixRequestContext context = HystrixRequestContext.initializeContext(); try { chain.doFilter(request, response); } finally { context.shutdown(); } } @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void destroy() { } }
在不同context中的缓存是不共享的,还有这个request内部一个ThreadLocal,所以request只能限于当前线程。
1.3 清除失效缓存
继承HystrixCommand或HystrixObservableCommand,在更新接口调用完成后,清空缓存。
import com.netflix.hystrix.HystrixCommand; import com.netflix.hystrix.HystrixCommandGroupKey; import com.netflix.hystrix.HystrixCommandKey; import com.szss.demo.orders.vo.UserVO; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.http.HttpEntity; import org.springframework.web.client.RestTemplate; public class UserUpdateCacheCommand extends HystrixCommand<UserVO> { private static final Logger LOGGER = LoggerFactory.getLogger(UserUpdateCacheCommand.class); private static final HystrixCommandKey GETTER_KEY = HystrixCommandKey.Factory.asKey("CommandKey"); private RestTemplate restTemplate; private UserVO user; public UserUpdateCacheCommand(RestTemplate restTemplate, UserVO user) { super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("userUpdateCacheCommand"))); this.restTemplate = restTemplate; this.user = user; } @Override protected UserVO run() throws Exception { LOGGER.info("thread:" + Thread.currentThread().getName()); HttpEntity<UserVO> u = new HttpEntity<UserVO>(user); UserVO userVO=restTemplate.postForObject("http://users-service/user",u,UserVO.class); UserCacheCommand.flushCache(user.getUsername()); return userVO; } // @Override // protected UserVO getFallback() { // UserVO user = new UserVO(); // user.setId(-1L); // user.setUsername("调用失败"); // return user; // } @Override protected String getCacheKey() { return user.getUsername(); } }
2 使用@CacheResult、@CacheRemove和@CacheKey标注来实现缓存
2.1 使用@CacheResult实现缓存功能
@CacheResult(cacheKeyMethod = "getCacheKey") @HystrixCommand(commandKey = "findUserById", groupKey = "UserService", threadPoolKey = "userServiceThreadPool") public UserVO findById(Long id) { ResponseEntity<UserVO> user = restTemplate.getForEntity("http://users-service/user?id={id}", UserVO.class, id); return user.getBody(); } public String getCacheKey(Long id) { return String.valueOf(id); }
@CacheResult注解中的cacheKeyMethod用来标示缓存key(cacheKey)的生成函数。函数的名称可任意取名,入参和标注@CacheResult的方法是一致的,返回类型是String。
2.2 使用@CacheResult和@CacheKey实现缓存功能
@CacheResult @HystrixCommand(commandKey = "findUserById", groupKey = "UserService", threadPoolKey = "userServiceThreadPool") public UserVO findById2(@CacheKey("id") Long id) { ResponseEntity<UserVO> user = restTemplate.getForEntity("http://users-service/user?id={id}", UserVO.class, id); return user.getBody(); }
标注@HystrixCommand注解的方法,使用@CacheKey标注需要指定的参数作为缓存key。
2.3 使用@CacheRemove清空缓存
@CacheRemove(commandKey = "findUserById") @HystrixCommand(commandKey = "updateUser",groupKey = "UserService",threadPoolKey = "userServiceThreadPool") public void updateUser(@CacheKey("id")UserVO user){ restTemplate.postForObject("http://users-service/user",user,UserVO.class); }
@CacheRemove必须指定commandKey,否则程序无法找到缓存位置。
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持脚本之家。
最新评论