1、 在一个请求执行之前,都必须先初始化一个requestcontext;
HystrixRequestContext context = HystrixRequestContext.initializeContext();
然后在请求结束之后,需要关闭request context
context.shutdown();
一般来说,在java web来的应用中,都是通过filter过滤器来实现的
filter:
/**
* hystrix请求上下文过滤器
* @author 张三丰
*
*/
public class HystrixRequestContextFilter implements Filter {
public void init(FilterConfig config) throws ServletException {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HystrixRequestContext context = HystrixRequestContext.initializeContext();
try {
chain.doFilter(request, response);
} catch (Exception e) {
e.printStackTrace();
} finally {
context.shutdown();
}
}
public void destroy() {
}
}
command:
/**
* 获取商品名称的command
* @author 张三丰
*
*/
public class GetProductNameCommand extends HystrixCommand<String> {
private Long productId;
public GetProductNameCommand(Long productId) {
super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("BrandInfoService"))
.andCommandKey(HystrixCommandKey.Factory.asKey("GetproductNameCommand"))
.andThreadPoolKey(HystrixThreadPoolKey.Factory.asKey("GetproductInfoPool"))
.andThreadPoolPropertiesDefaults(HystrixThreadPoolProperties.Setter()//配置线程池
.withCoreSize(15)
.withQueueSizeRejectionThreshold(10))
.andCommandPropertiesDefaults(HystrixCommandProperties.Setter()//配置信号量(这个参数设置了HystrixCommand.getFallback()最大允许的tomcat并发请求数量,默认值是10,也是通过semaphore信号量的机制去限流如果超出了这个最大值,那么直接被reject)
.withFallbackIsolationSemaphoreMaxConcurrentRequests(15))
);
this.productId = productId;
}
@Override
protected String run() throws Exception {
// 调用一个商品服务的接口(对于同一个请求,会被缓存,比如productId=100的商品请求两次,那么第二次会直接查缓存,不会进到这里)
// 如果调用失败了,报错了,那么就会去调用fallback降级机制
throw new Exception();
}
//抛出异常,走降级接口
@Override
protected String getFallback() {
//从缓存拿数据,尽量别走网络,如果非得走网络,需要再次调用command
System.out.println("从本地缓存获取商品数据,productId=" + productId);
return "商品名称";
}
//开启请求缓存
@Override
protected String getCacheKey() {
return "product_info_" + productId;
}
}
controller中:
@RequestMapping("/getProductInfos")
@ResponseBody
public String getProductInfos(Long productId) {
GetProductInfoCommand getProductInfoCommand = new GetProductInfoCommand(productId);
ProductInfo productInfo = getProductInfoCommand.execute();
System.out.println(productInfo);
System.out.println(getProductInfoCommand.isResponseFromCache());
return "success";
}