zuul1.3源碼扒一扒（1）

先開個頭吧

做爲偶爾點進源碼的時候看到東西，或是學到，或是不解，或是驚訝，以後的一些記錄。從springcloud各個組件開始吧，計劃文段保持間斷，只道出核心點，不過各個文段保持連續。

zuul做爲spring cloud 推薦網關，搭建起來很方便。

Spring Cloud 1.4.4 core jar包裏面的package基本描述了整個微服務架構的核心部分，其中zuul也囊括其中。

在使用zuul時咱們會使用EnableZuulProxy註解，配合使用spring cloud。

@EnableCircuitBreaker
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(ZuulProxyMarkerConfiguration.class)
public @interface EnableZuulProxy {
}

@EnableCircuitBreaker 默認使用斷路器 參考文檔：https://martinfowler.com/bliki/CircuitBreaker.html

@Import(ZuulProxyMarkerConfiguration.class)就技巧了。

@Configuration
public class ZuulProxyMarkerConfiguration {
   @Bean
   public Marker zuulProxyMarkerBean() {
      return new Marker();
   }

   class Marker {
   }
}

啥都沒幹，就是配置了個zuulProxyMarkerBean。看字面意思就猜差很少了，這個東西能夠用於標記，標記都是用來判斷什麼用的。
用於ZuulProxyAutoConfiguration的ConditionalOnBean，也就是使用EnableZuulProxy註解連帶的開啓了ZuulProxyAutoConfiguration的配置。

還有個註解 EnableZuulServer 同樣有個ZuulServerMarkerConfiguration 同樣的道理。
事實上EnableZuulProxy是EnableZuulServer的加強版，爲何，由於ZuulProxyAutoConfiguration繼承ZuulServerAutoConfiguration。

那麼zuul的配置文件裏有什麼呢？我以爲最重要的一個spring cloud網關要組合兩個組件：一個是Ribbon，一個是hystrix，後者簽名經過EnableCircuitBreaker搞進來了，後續在寫。
核心關注兩個類：ZuulProxyAutoConfiguration 和 ZuulServerAutoConfiguration

@Configuration
@Import({ RibbonCommandFactoryConfiguration.RestClientRibbonConfiguration.class,
        RibbonCommandFactoryConfiguration.OkHttpRibbonConfiguration.class,
        RibbonCommandFactoryConfiguration.HttpClientRibbonConfiguration.class,
        HttpClientConfiguration.class })
@ConditionalOnBean(ZuulProxyMarkerConfiguration.Marker.class)
public class ZuulProxyAutoConfiguration extends ZuulServerAutoConfiguration {

    @SuppressWarnings("rawtypes")
    @Autowired(required = false)
    private List<RibbonRequestCustomizer> requestCustomizers = Collections.emptyList();

    @Autowired(required = false)
    private Registration registration;

    @Autowired
    private DiscoveryClient discovery;

    @Autowired
    private ServiceRouteMapper serviceRouteMapper;

    @Override
    public HasFeatures zuulFeature() {
        return HasFeatures.namedFeature("Zuul (Discovery)",
                ZuulProxyAutoConfiguration.class);
    }

    @Bean
    @ConditionalOnMissingBean(DiscoveryClientRouteLocator.class)
    public DiscoveryClientRouteLocator discoveryRouteLocator() {
        return new DiscoveryClientRouteLocator(this.server.getServletPrefix(),
                this.discovery, this.zuulProperties, this.serviceRouteMapper, this.registration);
    }

    // pre filters
    @Bean
    public PreDecorationFilter preDecorationFilter(RouteLocator routeLocator,
            ProxyRequestHelper proxyRequestHelper) {
        return new PreDecorationFilter(routeLocator, this.server.getServletPrefix(),
                this.zuulProperties, proxyRequestHelper);
    }

    // route filters
    @Bean
    public RibbonRoutingFilter ribbonRoutingFilter(ProxyRequestHelper helper,
            RibbonCommandFactory<?> ribbonCommandFactory) {
        RibbonRoutingFilter filter = new RibbonRoutingFilter(helper, ribbonCommandFactory,
                this.requestCustomizers);
        return filter;
    }

    @Bean
    @ConditionalOnMissingBean({SimpleHostRoutingFilter.class, CloseableHttpClient.class})
    public SimpleHostRoutingFilter simpleHostRoutingFilter(ProxyRequestHelper helper,
            ZuulProperties zuulProperties,
            ApacheHttpClientConnectionManagerFactory connectionManagerFactory,
            ApacheHttpClientFactory httpClientFactory) {
        return new SimpleHostRoutingFilter(helper, zuulProperties,
                connectionManagerFactory, httpClientFactory);
    }

    @Bean
    @ConditionalOnMissingBean({SimpleHostRoutingFilter.class})
    public SimpleHostRoutingFilter simpleHostRoutingFilter2(ProxyRequestHelper helper,
                                                           ZuulProperties zuulProperties,
                                                           CloseableHttpClient httpClient) {
        return new SimpleHostRoutingFilter(helper, zuulProperties,
                httpClient);
    }

    @Bean
    public ApplicationListener<ApplicationEvent> zuulDiscoveryRefreshRoutesListener() {
        return new ZuulDiscoveryRefreshListener();
    }

    @Bean
    @ConditionalOnMissingBean(ServiceRouteMapper.class)
    public ServiceRouteMapper serviceRouteMapper() {
        return new SimpleServiceRouteMapper();
    }

    @Configuration
    @ConditionalOnMissingClass("org.springframework.boot.actuate.endpoint.Endpoint")
    protected static class NoActuatorConfiguration {

        @Bean
        public ProxyRequestHelper proxyRequestHelper(ZuulProperties zuulProperties) {
            ProxyRequestHelper helper = new ProxyRequestHelper();
            helper.setIgnoredHeaders(zuulProperties.getIgnoredHeaders());
            helper.setTraceRequestBody(zuulProperties.isTraceRequestBody());
            return helper;
        }

    }

    @Configuration
    @ConditionalOnClass(Endpoint.class)
    protected static class EndpointConfiguration {

        @Autowired(required = false)
        private TraceRepository traces;

        @ConditionalOnEnabledEndpoint("routes")
        @Bean
        public RoutesEndpoint routesEndpoint(RouteLocator routeLocator) {
            return new RoutesEndpoint(routeLocator);
        }

        @ConditionalOnEnabledEndpoint("routes")
        @Bean
        public RoutesMvcEndpoint routesMvcEndpoint(RouteLocator routeLocator,
                RoutesEndpoint endpoint) {
            return new RoutesMvcEndpoint(endpoint, routeLocator);
        }

        @ConditionalOnEnabledEndpoint("filters")
        @Bean
        public FiltersEndpoint filtersEndpoint() {
            FilterRegistry filterRegistry = FilterRegistry.instance();
            return new FiltersEndpoint(filterRegistry);
        }

        @Bean
        public ProxyRequestHelper proxyRequestHelper(ZuulProperties zuulProperties) {
            TraceProxyRequestHelper helper = new TraceProxyRequestHelper();
            if (this.traces != null) {
                helper.setTraces(this.traces);
            }
            helper.setIgnoredHeaders(zuulProperties.getIgnoredHeaders());
            helper.setTraceRequestBody(zuulProperties.isTraceRequestBody());
            return helper;
        }
    }

    private static class ZuulDiscoveryRefreshListener
            implements ApplicationListener<ApplicationEvent> {

        private HeartbeatMonitor monitor = new HeartbeatMonitor();

        @Autowired
        private ZuulHandlerMapping zuulHandlerMapping;

        @Override
        public void onApplicationEvent(ApplicationEvent event) {
            if (event instanceof InstanceRegisteredEvent) {
                reset();
            }
            else if (event instanceof ParentHeartbeatEvent) {
                ParentHeartbeatEvent e = (ParentHeartbeatEvent) event;
                resetIfNeeded(e.getValue());
            }
            else if (event instanceof HeartbeatEvent) {
                HeartbeatEvent e = (HeartbeatEvent) event;
                resetIfNeeded(e.getValue());
            }

        }

        private void resetIfNeeded(Object value) {
            if (this.monitor.update(value)) {
                reset();
            }
        }

        private void reset() {
            this.zuulHandlerMapping.setDirty(true);
        }

    }

}

@Configuration
@EnableConfigurationProperties({ ZuulProperties.class })
@ConditionalOnClass(ZuulServlet.class)
@ConditionalOnBean(ZuulServerMarkerConfiguration.Marker.class)
// Make sure to get the ServerProperties from the same place as a normal web app would
@Import(ServerPropertiesAutoConfiguration.class)
public class ZuulServerAutoConfiguration {

    @Autowired
    protected ZuulProperties zuulProperties;

    @Autowired
    protected ServerProperties server;

    @Autowired(required = false)
    private ErrorController errorController;

    @Bean
    public HasFeatures zuulFeature() {
        return HasFeatures.namedFeature("Zuul (Simple)", ZuulServerAutoConfiguration.class);
    }

    @Bean
    @Primary
    public CompositeRouteLocator primaryRouteLocator(
            Collection<RouteLocator> routeLocators) {
        return new CompositeRouteLocator(routeLocators);
    }

    @Bean
    @ConditionalOnMissingBean(SimpleRouteLocator.class)
    public SimpleRouteLocator simpleRouteLocator() {
        return new SimpleRouteLocator(this.server.getServletPrefix(),
                this.zuulProperties);
    }

    @Bean
    public ZuulController zuulController() {
        return new ZuulController();
    }

    @Bean
    public ZuulHandlerMapping zuulHandlerMapping(RouteLocator routes) {
        ZuulHandlerMapping mapping = new ZuulHandlerMapping(routes, zuulController());
        mapping.setErrorController(this.errorController);
        return mapping;
    }

    @Bean
    public ApplicationListener<ApplicationEvent> zuulRefreshRoutesListener() {
        return new ZuulRefreshListener();
    }

    @Bean
    @ConditionalOnMissingBean(name = "zuulServlet")
    public ServletRegistrationBean zuulServlet() {
        ServletRegistrationBean servlet = new ServletRegistrationBean(new ZuulServlet(),
                this.zuulProperties.getServletPattern());
        // The whole point of exposing this servlet is to provide a route that doesn't
        // buffer requests.
        servlet.addInitParameter("buffer-requests", "false");
        return servlet;
    }

    // pre filters

    @Bean
    public ServletDetectionFilter servletDetectionFilter() {
        return new ServletDetectionFilter();
    }

    @Bean
    public FormBodyWrapperFilter formBodyWrapperFilter() {
        return new FormBodyWrapperFilter();
    }

    @Bean
    public DebugFilter debugFilter() {
        return new DebugFilter();
    }

    @Bean
    public Servlet30WrapperFilter servlet30WrapperFilter() {
        return new Servlet30WrapperFilter();
    }

    // post filters

    @Bean
    public SendResponseFilter sendResponseFilter() {
        return new SendResponseFilter();
    }

    @Bean
    public SendErrorFilter sendErrorFilter() {
        return new SendErrorFilter();
    }

    @Bean
    public SendForwardFilter sendForwardFilter() {
        return new SendForwardFilter();
    }

    @Bean
    @ConditionalOnProperty(value = "zuul.ribbon.eager-load.enabled", matchIfMissing = false)
    public ZuulRouteApplicationContextInitializer zuulRoutesApplicationContextInitiazer(
            SpringClientFactory springClientFactory) {
        return new ZuulRouteApplicationContextInitializer(springClientFactory,
                zuulProperties);
    }

    @Configuration
    protected static class ZuulFilterConfiguration {

        @Autowired
        private Map<String, ZuulFilter> filters;

        @Bean
        public ZuulFilterInitializer zuulFilterInitializer(
                CounterFactory counterFactory, TracerFactory tracerFactory) {
            FilterLoader filterLoader = FilterLoader.getInstance();
            FilterRegistry filterRegistry = FilterRegistry.instance();
            return new ZuulFilterInitializer(this.filters, counterFactory, tracerFactory, filterLoader, filterRegistry);
        }

    }

    @Configuration
    @ConditionalOnClass(CounterService.class)
    protected static class ZuulCounterFactoryConfiguration {

        @Bean
        @ConditionalOnBean(CounterService.class)
        public CounterFactory counterFactory(CounterService counterService) {
            return new DefaultCounterFactory(counterService);
        }
    }

    @Configuration
    protected static class ZuulMetricsConfiguration {

        @Bean
        @ConditionalOnMissingBean(CounterFactory.class)
        public CounterFactory counterFactory() {
            return new EmptyCounterFactory();
        }

        @ConditionalOnMissingBean(TracerFactory.class)
        @Bean
        public TracerFactory tracerFactory() {
            return new EmptyTracerFactory();
        }

    }

    private static class ZuulRefreshListener
            implements ApplicationListener<ApplicationEvent> {

        @Autowired
        private ZuulHandlerMapping zuulHandlerMapping;

        private HeartbeatMonitor heartbeatMonitor = new HeartbeatMonitor();

        @Override
        public void onApplicationEvent(ApplicationEvent event) {
            if (event instanceof ContextRefreshedEvent
                    || event instanceof RefreshScopeRefreshedEvent
                    || event instanceof RoutesRefreshedEvent) {
                this.zuulHandlerMapping.setDirty(true);
            }
            else if (event instanceof HeartbeatEvent) {
                if (this.heartbeatMonitor.update(((HeartbeatEvent) event).getValue())) {
                    this.zuulHandlerMapping.setDirty(true);
                }
            }
        }

    }

}