Netflix---Hystrix文档翻译--01
Executive Summary
核心观点（金字塔原理）
结论先行: Hystrix是Netflix开源的容错库，通过Command模式封装服务调用，支持同步、异步和响应式三种执行方式，实现服务降级和熔断保护。
支撑论点:
- Command模式封装：通过HystrixCommand和HystrixObservableCommand两种方式封装远程调用逻辑
- 多种执行方式：支持execute()同步执行、queue()异步执行、observe()/toObservable()响应式执行
- 线程隔离：通过HystrixCommandGroupKey进行命令分组，实现资源隔离和监控
SWOT 分析
| 维度 | 分析 |
|---|---|
| S 优势 | Netflix大规模生产验证；API设计简洁优雅；支持多种执行模式；与RxJava深度集成 |
| W 劣势 | 项目已进入维护模式；学习曲线较陡；Observable模式理解成本高 |
| O 机会 | 微服务架构的服务容错；分布式系统的弹性设计；服务降级和熔断场景 |
| T 威胁 | Resilience4j等新一代容错库的竞争；Spring Cloud Circuit Breaker抽象层的出现 |
适用场景
- 微服务架构中的服务间调用保护
- 需要实现服务降级和熔断的分布式系统
- 对第三方依赖调用的容错处理
Hello World!
public class CommandHelloWorld extends HystrixCommand<String> {
private final String name;
public CommandHelloWorld(String name) {
super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"));
this.name = name;
}
@Override
protected String run() {
// a real example would do work like a network call here
return "Hello " + name + "!";
}
}
//另一种方式，使用HystrixObservableCommand替代HystrixCommand需要覆盖其构造方法。
public class CommandHelloWorld extends HystrixObservableCommand<String> {
private final String name;
public CommandHelloWorld(String name) {
super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"));
this.name = name;
}
@Override
protected Observable<String> construct() {
return Observable.create(new Observable.OnSubscribe<String>() {
@Override
public void call(Subscriber<? super String> observer) {
try {
if (!observer.isUnsubscribed()) {
// a real example would do work like a network call here
observer.onNext("Hello");
observer.onNext(name + "!");
observer.onCompleted();
}
} catch (Exception e) {
observer.onError(e);
}
}
} ).subscribeOn(Schedulers.io());
}
}
同步执行 Synchronous Execution
- 使用HystrixCommand的方式时，可以运行execute()方法,以及对应的测试用例
String s = new CommandHelloWorld("World").execute(); @Test public void testSynchronous() { assertEquals("Hello World!", new CommandHelloWorld("World").execute()); assertEquals("Hello Bob!", new CommandHelloWorld("Bob").execute()); }HystrixObservableCommand Equivalent
- There is no simple equivalent to execute for a HystrixObservableCommand, but if you know that the Observable produced by such a command must always produce only a single value, you can mimic the behavior of execute by applying .toBlocking().toFuture().get() to the Observable.
异步执行 Asynchronous Execution
- 使用HystrixCommand的方式时，queue()方法执行。
Future<String> fs = new CommandHelloWorld("World").queue();
String s = fs.get();//获取结果
@Test
public void testAsynchronous1() throws Exception {
assertEquals("Hello World!", new CommandHelloWorld("World").queue().get());
assertEquals("Hello Bob!", new CommandHelloWorld("Bob").queue().get());
}
@Test
public void testAsynchronous2() throws Exception {
Future<String> fWorld = new CommandHelloWorld("World").queue();
Future<String> fBob = new CommandHelloWorld("Bob").queue();
assertEquals("Hello World!", fWorld.get());
assertEquals("Hello Bob!", fBob.get());
}
- 两种执行方式结果相同
String s1 = new CommandHelloWorld("World").execute(); String s2 = new CommandHelloWorld("World").queue().get();
HystrixObservableCommand Equivalent
- There is no simple equivalent to queue for a HystrixObservableCommand, but if you know that the Observable produced by such a command must always produce only a single value, you can mimic the behavior of queue by applying the RxJava operators .toBlocking().toFuture() to the Observable.