聊聊spring cloud的HystrixAutoConfiguration

/**
 * Auto configuration for Hystrix.
 *
 * @author Christian Dupuis
 * @author Dave Syer
 */
@Configuration
@ConditionalOnClass({ Hystrix.class, HealthIndicator.class })
@AutoConfigureAfter({ HealthIndicatorAutoConfiguration.class })
public class HystrixAutoConfiguration {

    @Bean
    @ConditionalOnEnabledHealthIndicator("hystrix")
    public HystrixHealthIndicator hystrixHealthIndicator() {
        return new HystrixHealthIndicator();
    }

    @Bean
    @ConditionalOnProperty(value = "management.metrics.hystrix.enabled", matchIfMissing = true)
    public HystrixMetricsBinder hystrixMetricsBinder() {
        return new HystrixMetricsBinder();
    }

    /**
     * See original {@link org.springframework.boot.actuate.autoconfigure.jolokia.JolokiaEndpointAutoConfiguration}
     */
    @Configuration
    @ConditionalOnWebApplication(type = SERVLET)
    @ConditionalOnBean(HystrixCommandAspect.class) // only install the stream if enabled
    @ConditionalOnClass({ HystrixMetricsStreamServlet.class })
    @EnableConfigurationProperties(HystrixProperties.class)
    protected static class HystrixServletAutoConfiguration {

        @Bean
        @ConditionalOnEnabledEndpoint
        public HystrixStreamEndpoint hystrixStreamEndpoint(HystrixProperties properties) {
            return new HystrixStreamEndpoint(properties.getConfig());
        }

        @Bean
        public HasFeatures hystrixStreamFeature() {
            return HasFeatures.namedFeature("Hystrix Stream Servlet", HystrixMetricsStreamServlet.class);
        }
    }

    @Configuration
    @ConditionalOnWebApplication(type = REACTIVE)
    @ConditionalOnBean(HystrixCommandAspect.class) // only install the stream if enabled
    @ConditionalOnClass({ DispatcherHandler.class })
    @EnableConfigurationProperties(HystrixProperties.class)
    protected static class HystrixWebfluxManagementContextConfiguration {

        @Bean
        @ConditionalOnEnabledEndpoint
        public HystrixWebfluxEndpoint hystrixWebfluxController() {
            Observable<String> serializedDashboardData = HystrixDashboardStream.getInstance().observe()
                    .concatMap(dashboardData -> Observable.from(SerialHystrixDashboardData.toMultipleJsonStrings(dashboardData)));
            Publisher<String> publisher = RxReactiveStreams.toPublisher(serializedDashboardData);
            return new HystrixWebfluxEndpoint(publisher);
        }

        @Bean
        public HasFeatures hystrixStreamFeature() {
            return HasFeatures.namedFeature("Hystrix Stream Webflux", HystrixWebfluxEndpoint.class);
        }
    }
}

/**
 * A {@link HealthIndicator} implementation for Hystrix circuit breakers.
 * <p>
 * This default implementation will not change the system state (e.g.  <code>OK</code>) but
 * includes all open circuits by name.
 *
 * @author Christian Dupuis
 */
public class HystrixHealthIndicator extends AbstractHealthIndicator {

    private static final Status CIRCUIT_OPEN = new Status("CIRCUIT_OPEN");

    @Override
    protected void doHealthCheck(Builder builder) throws Exception {
        List<String> openCircuitBreakers = new ArrayList<>();

        // Collect all open circuit breakers from Hystrix
        for (HystrixCommandMetrics metrics : HystrixCommandMetrics.getInstances()) {
            HystrixCircuitBreaker circuitBreaker = HystrixCircuitBreaker.Factory
                    .getInstance(metrics.getCommandKey());
            if (circuitBreaker != null && circuitBreaker.isOpen()) {
                openCircuitBreakers.add(metrics.getCommandGroup().name() + "::"
                        + metrics.getCommandKey().name());
            }
        }

        // If there is at least one open circuit report OUT_OF_SERVICE adding the command
        // group
        // and key name
        if (!openCircuitBreakers.isEmpty()) {
            builder.status(CIRCUIT_OPEN).withDetail("openCircuitBreakers",
                    openCircuitBreakers);
        }
        else {
            builder.up();
        }
    }

}

@NonNullApi
@NonNullFields
public class HystrixMetricsBinder implements MeterBinder {

    @Override
    public void bindTo(MeterRegistry registry) {
        // Keeps references of existing Hystrix plugins.
        HystrixEventNotifier eventNotifier = HystrixPlugins.getInstance().getEventNotifier();
        HystrixPropertiesStrategy propertiesStrategy = HystrixPlugins.getInstance().getPropertiesStrategy();
        HystrixCommandExecutionHook commandExecutionHook = HystrixPlugins.getInstance().getCommandExecutionHook();
        HystrixConcurrencyStrategy concurrencyStrategy = HystrixPlugins.getInstance().getConcurrencyStrategy();

        HystrixPlugins.reset();

        // Registers existing plugins except the new MicroMeter Strategy plugin.
        HystrixPlugins.getInstance().registerMetricsPublisher(new MicrometerMetricsPublisher(registry));
        HystrixPlugins.getInstance().registerConcurrencyStrategy(concurrencyStrategy);
        HystrixPlugins.getInstance().registerEventNotifier(eventNotifier);
        HystrixPlugins.getInstance().registerPropertiesStrategy(propertiesStrategy);
        HystrixPlugins.getInstance().registerCommandExecutionHook(commandExecutionHook);
    }
}

/**
 * {@link org.springframework.boot.actuate.endpoint.annotation.Endpoint} to expose a Jolokia {@link HystrixMetricsStreamServlet}.
 *
 * @author Phillip Webb
 * @since 2.0.0
 */
@ServletEndpoint(id = "hystrix.stream")
public class HystrixStreamEndpoint implements Supplier<EndpointServlet> {

    private final Map<String, String> initParameters;

    public HystrixStreamEndpoint(Map<String, String> initParameters) {
        this.initParameters = initParameters;
    }

    @Override
    public EndpointServlet get() {
        return new EndpointServlet(HystrixMetricsStreamServlet.class)
                .withInitParameters(this.initParameters);
    }
}

@RestControllerEndpoint(id = "hystrix.stream")
public class HystrixWebfluxEndpoint {

    private final Flux<String> stream;

    public HystrixWebfluxEndpoint(Publisher<String> dashboardData) {
        stream = Flux.interval(Duration.ofMillis(500)).map(aLong -> "{\"type\":\"ping\"}")
                .mergeWith(dashboardData).share();
    }

    // path needs to be empty, so it registers correct as /actuator/hystrix.stream
    @GetMapping(path = "", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
    public Flux<String> hystrixStream() {
        return stream;
    }
}