Gateway processing flow of Zuul source code analysis

Posted by jeffrydell on Tue, 08 Feb 2022 09:26:56 +0100

Zuul processing flow

1, Spring cloud starter zuul starter

Let's first check what's under the spring cloud starter zuul starter package. The focus here is POM XML file, zuuldeprectationwarningautoconfiguration java
Open org springframework. cloud/spring-cloud-starter-zuul/pom. XML, you can see that it depends on spring cloud starter Netflix zuul

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 <modelVersion>4.0.0</modelVersion>
 <parent>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-netflix</artifactId>
  <version>2.2.5.RELEASE</version>
  <relativePath>..</relativePath> <!-- lookup parent from repository -->
 </parent>
 <artifactId>spring-cloud-starter-zuul</artifactId>
 <name>spring-cloud-starter-zuul</name>
 <description>Spring Cloud Starter Zuul (deprecated, please use spring-cloud-starter-netflix-zuul)</description>
 <url>https://projects.spring.io/spring-cloud</url>
 <organization>
  <name>Pivotal Software, Inc.</name>
  <url>https://www.spring.io</url>
 </organization>
 <properties>
  <main.basedir>${basedir}/../..</main.basedir>
 </properties>
 <dependencies>
  <dependency>
   <groupId>org.springframework.cloud</groupId>
   <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
  </dependency>
 </dependencies>
</project>

Let's look at the spring cloud starter Netflix zuul package
Open POM XML can be seen to depend on COM netflix. Zuul, so Spring Cloud Zuul is based on zuul of Netflix company. In addition, it also adds hystrix and ribbon dependencies. Therefore, zuul comes with these two functions. Spring boot starter web dependency can make the application become a web application, and spring boot starter actuator is a monitoring dependency

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix</artifactId>
        <version>2.2.5.RELEASE</version>
    </parent>
    <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
    <name>Spring Cloud Starter Netflix Zuul</name>
    <description>Spring Cloud Starter Netflix Zuul</description>
    <url>https://projects.spring.io/spring-cloud</url>
    <organization>
        <name>Pivotal Software, Inc.</name>
        <url>https://www.spring.io</url>
    </organization>
    <properties>
        <main.basedir>${basedir}/../../..</main.basedir>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-archaius</artifactId>
        </dependency>
        <dependency>
            <groupId>com.netflix.zuul</groupId>
            <artifactId>zuul-core</artifactId>
        </dependency>
    </dependencies>
</project>

/META-INF/spring. Providers relies on spring platform Netflix core module and zuul core module
1 provides: spring-platform-netflix-core, zuul-core
Now let's go to Spring platform Netflix core to see how Spring integrates a series of Netflix frameworks. The following is the code framework diagram
As you can see, the JAR package also contains spring Factories file, so this configuration file will be retrieved when the SpringBoot project starts. This file is the key to the automatic registration configuration of zuul. You can see the familiar automatic configuration classes of zuul, hystrix, feign and ribbon below

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.netflix.archaius.ArchaiusAutoConfiguration,\
org.springframework.cloud.netflix.feign.ribbon.FeignRibbonClientAutoConfiguration,\
org.springframework.cloud.netflix.feign.FeignAutoConfiguration,\
org.springframework.cloud.netflix.feign.encoding.FeignAcceptGzipEncodingAutoConfiguration,\
org.springframework.cloud.netflix.feign.encoding.FeignContentGzipEncodingAutoConfiguration,\
org.springframework.cloud.netflix.hystrix.HystrixAutoConfiguration,\
org.springframework.cloud.netflix.hystrix.security.HystrixSecurityAutoConfiguration,\
org.springframework.cloud.netflix.ribbon.RibbonAutoConfiguration,\
org.springframework.cloud.netflix.rx.RxJavaAutoConfiguration,\
org.springframework.cloud.netflix.metrics.servo.ServoMetricsAutoConfiguration,\
org.springframework.cloud.netflix.zuul.ZuulServerAutoConfiguration,\
org.springframework.cloud.netflix.zuul.ZuulProxyAutoConfiguration

org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker=\
org.springframework.cloud.netflix.hystrix.HystrixCircuitBreakerConfiguration

org.springframework.boot.env.EnvironmentPostProcessor=\
org.springframework.cloud.netflix.metrics.ServoEnvironmentPostProcessor

We are now concerned about zuul's automatic configuration class, from spring. Com above In the factories file, you can see that two classes are automatically configured related to zuul. The following figure shows that these two classes have inheritance relationship. Zuul proxyautoconfiguration has the most complete function
ZuulServerAutoConfiguration and ZuulProxyAutoConfiguration
Zuulserver autoconfiguration automatically configures the class. If there is @ EnableZuulServer on the startup class, this class will take effect
1. In the following code, we can see that @ Conditional is widely used as the condition judgment. Note that ZuulController Bean is the request entry of Zuul. This class implements the Controller. It indicates that spring MVC dispatcher servlet is also used here,
2. At the same time, this class has registered a large number of zuulfilters
3. Code:

/**
 * @author
 */
@Configuration // Declaration is a configuration class
@EnableConfigurationProperties({ ZuulProperties.class }) // Activate zuul configuration
@ConditionalOnClass(ZuulServlet.class) // Condition 1 zuulservlet exists class
@ConditionalOnBean(ZuulServerMarkerConfiguration.Marker.class) // Zuulservermarkerconfiguration exists in condition 2 Marker. Class bean, that is, the application uses @ EnableZuulServer annotation
// Make sure to get the ServerProperties from the same place as a normal web app would
@Import(ServerPropertiesAutoConfiguration.class) // Configure ServerProperties instance
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);
    }

    /**
     * zuulController, A ZuulServlet type servlet is packaged to initialize the ZuulServlet type servlet
     *
     * @return
     */
    @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);
                }
            }
        }

    }

}

ZuulProxyAutoConfiguration automatic configuration class. If there is a corresponding @ EnableZuulProxy on the startup class, this class will take effect
From the inheritance diagram of the above class, it can be found that this class inherits zuulserver autoconfiguration, so this class has all the functions of zuulserver autoconfiguration, and adds the function of using service discovery as routing addressing on this basis
code:

/**
 * @author
 */
@Configuration // Declaration is a configuration class
@Import({ RibbonCommandFactoryConfiguration.RestClientRibbonConfiguration.class, // Introducing RibbonCommandFactory configuration
        RibbonCommandFactoryConfiguration.OkHttpRibbonConfiguration.class,
        RibbonCommandFactoryConfiguration.HttpClientRibbonConfiguration.class,
        HttpClientConfiguration.class })
@ConditionalOnBean(ZuulProxyMarkerConfiguration.Marker.class) // Zuulproxymarkerconfiguration exists in condition 2 Marker. The @ enableproxy annotation is used
public class ZuulProxyAutoConfiguration extends ZuulServerAutoConfiguration {

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

    /**
     * Gateway service registration instance information
     */
    @Autowired(required = false)
    private Registration registration;

    /**
     * Service discovery client
     */
    @Autowired
    private DiscoveryClient discovery;

    /**
     * serviceId Mapping logic for and routing
     */
    @Autowired
    private ServiceRouteMapper serviceRouteMapper;

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

    /**
     * Static and dynamic route addressing: statically obtained from the configuration file and dynamically completed through the service discovery client The latter has higher priority
     * @return
     */
    @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;
        }

    }

    /**
     * Add Endpoint
     */
    @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);
        }

    }

}

Which mode zuulserver autoconfiguration and ZuulProxyAutoConfiguration use is distinguished by @ EnableZuulServer and @ EnableZuulProxy annotations respectively
The former uses ZuulProperties to configure routing addressing;
The latter adds the service discovery as the routing addressing function on the basis of the original, and uses the Ribbon as the load balancing of the client, which is the most commonly used;

2, @ EnableZuulProxy

@EnableZuulProxy annotation

/**
 * Sets up a Zuul server endpoint and installs some reverse proxy filters in it, so it can
 * forward requests to backend servers. The backends can be registered manually through
 * configuration or via DiscoveryClient.
 *
 * @see EnableZuulServer for how to get a Zuul server without any proxying
 *
 * @author
 */
@EnableCircuitBreaker
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(ZuulProxyMarkerConfiguration.class)
public @interface EnableZuulProxy {
}

@EnableZuulProxy analysis
@The enablercircuitbreaker annotation is used to turn on the circuit breaker function

/**
 * Annotation to enable a CircuitBreaker implementation.
 * http://martinfowler.com/bliki/CircuitBreaker.html
 * @author
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(EnableCircuitBreakerImportSelector.class)
public @interface EnableCircuitBreaker {

}

@Import(ZuulProxyMarkerConfiguration.class)
ZuulProxyMarkerConfiguration.Marker.class

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

    class Marker {
    }
}

3, Use Consul as the registry

@zuul in EnableZuulProxy mode needs the support of the registry, because eureka has been abandoned. I choose Consul here

1. Add Maven dependency

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-consul-discovery</artifactId>
</dependency>

2. Add @ EnableDiscoveryClient annotation on the startup class

@EnableZuulProxy
@EnableDiscoveryClient
@SpringBootApplication
public class ZuulApplication {

    public static void main(String[] args) {
        SpringApplication.run(ZuulApplication.class, args);
    }

}

3. After all the above steps, the Zuul application of the whole service gateway can play a role

4, Summary

It is more convenient to add a spring-zuul-cloud-enable application to the netspring-zuul cloud startup environment by adding a spring-zuul-cloud.zuul package.
2.Spring Cloud Zuul actually adds some zuulfilters on the basis of servlets to complete some extra things. After encapsulation, it becomes a framework.

Topics: Back-end source code source code analysis gateway zuul

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