1 /**
2 * CommandWithFallbackViaNetwork.run模拟远程调用失败，FallbackViaNetwork模拟需要通过网络从Redis获取老数据
3 */
4 public class CommandWithFallbackViaNetwork extends HystrixCommand<String> {
5 private final int id;
6
7 protected CommandWithFallbackViaNetwork(int id) {
8 //不设置ThreadPoolKey时，ThreadPoolKey默认为groupKey，不同的threadPoolKey代表不同的线程池。
9 //A group name for a HystrixCommand. This is used for grouping together commands such as for reporting, alerting, dashboards or team/library ownership.
10 super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceX"))
11 //A key to represent a HystrixCommand for monitoring, circuit-breakers, metrics publishing, caching and other such uses.
12 .andCommandKey(HystrixCommandKey.Factory.asKey("GetValueCommand"))
13 .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
14 .withExecutionIsolationStrategy(HystrixCommandProperties.ExecutionIsolationStrategy.THREAD)));
15 this.id = id;
16 }
17
18 @Override
19 protected String run() {
20 // remoteServiceXClient.getValue(id);
21 //模拟远程调用失败
22 throw new RuntimeException("force failure for example");
23 }
24
25 @Override
26 protected String getFallback() {
27 return new FallbackViaNetwork(id).execute();
28 }
29
30 private static class FallbackViaNetwork extends HystrixCommand<String> {
31 private final int id;
32 private static Map<Integer, String> memCacheClient = new ConcurrentHashMap<>();//充当Redis缓存，需要访问网络
33
34 public FallbackViaNetwork(int id) {
35 //groupKey与CommandWithFallbackViaNetwork一致，
36 super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceX"))
37 .andCommandKey(HystrixCommandKey.Factory.asKey("GetValueFallbackCommand"))
38 // use a different threadpool for the fallback command
39 // so saturating the RemoteServiceX pool won't prevent
40 // fallbacks from executing
41 .andThreadPoolKey(HystrixThreadPoolKey.Factory.asKey("RemoteServiceXFallback")));
42 this.id = id;
43 }
44
45 @Override
46 protected String run() {
47 return memCacheClient.get(id);
48 }
49
50 @Override
51 protected String getFallback() {
52 // the fallback also failed
53 // so this fallback-of-a-fallback will
54 // fail silently and return null
55 return null;
56 }
57 }
58 }
