聊聊spring cloud的DiscoveryClientRouteDefinitionLocator

序

本文主要研究一下spring cloud的DiscoveryClientRouteDefinitionLocator

GatewayAutoConfiguration

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@Configuration
@ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true)
@EnableConfigurationProperties
@AutoConfigureBefore(HttpHandlerAutoConfiguration.class)
@AutoConfigureAfter({GatewayLoadBalancerClientAutoConfiguration.class, GatewayClassPathWarningAutoConfiguration.class})
@ConditionalOnClass(DispatcherHandler.class)
public class GatewayAutoConfiguration {
	//......
	@Bean
	@ConditionalOnMissingBean
	public PropertiesRouteDefinitionLocator propertiesRouteDefinitionLocator(GatewayProperties properties) {
		return new PropertiesRouteDefinitionLocator(properties);
	}

	@Bean
	@ConditionalOnMissingBean(RouteDefinitionRepository.class)
	public InMemoryRouteDefinitionRepository inMemoryRouteDefinitionRepository() {
		return new InMemoryRouteDefinitionRepository();
	}
	@Bean
	@Primary
	public RouteDefinitionLocator routeDefinitionLocator(List<RouteDefinitionLocator> routeDefinitionLocators) {
		return new CompositeRouteDefinitionLocator(Flux.fromIterable(routeDefinitionLocators));
	}
	//......
}
复制代码

这里注册了CompositeRouteDefinitionLocator

GatewayDiscoveryClientAutoConfiguration

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/discovery/GatewayDiscoveryClientAutoConfiguration.java

@Configuration
@ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true)
@AutoConfigureBefore(GatewayAutoConfiguration.class)
@ConditionalOnClass({DispatcherHandler.class, DiscoveryClient.class})
@EnableConfigurationProperties
public class GatewayDiscoveryClientAutoConfiguration {

	@Bean
	@ConditionalOnBean(DiscoveryClient.class)
	@ConditionalOnProperty(name = "spring.cloud.gateway.discovery.locator.enabled")
	public DiscoveryClientRouteDefinitionLocator discoveryClientRouteDefinitionLocator(
			DiscoveryClient discoveryClient, DiscoveryLocatorProperties properties) {
		return new DiscoveryClientRouteDefinitionLocator(discoveryClient, properties);
	}

	@Bean
	public DiscoveryLocatorProperties discoveryLocatorProperties() {
		DiscoveryLocatorProperties properties = new DiscoveryLocatorProperties();
		properties.setPredicates(initPredicates());
		properties.setFilters(initFilters());
		return properties;
	}

	public static List<PredicateDefinition> initPredicates() {
		ArrayList<PredicateDefinition> definitions = new ArrayList<>();
		// TODO: add a predicate that matches the url at /serviceId?

		// add a predicate that matches the url at /serviceId/**
		PredicateDefinition predicate = new PredicateDefinition();
		predicate.setName(normalizeRoutePredicateName(PathRoutePredicateFactory.class));
		predicate.addArg(PATTERN_KEY, "'/'+serviceId+'/**'");
		definitions.add(predicate);
		return definitions;
	}

	public static List<FilterDefinition> initFilters() {
		ArrayList<FilterDefinition> definitions = new ArrayList<>();

		// add a filter that removes /serviceId by default
		FilterDefinition filter = new FilterDefinition();
		filter.setName(normalizeFilterFactoryName(RewritePathGatewayFilterFactory.class));
		String regex = "'/' + serviceId + '/(?<remaining>.*)'";
		String replacement = "'/${remaining}'";
		filter.addArg(REGEXP_KEY, regex);
		filter.addArg(REPLACEMENT_KEY, replacement);
		definitions.add(filter);

		return definitions;
	}

}
复制代码

默认配置了一个根据serviceId进行rewrite的filter

DiscoveryLocatorProperties

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/discovery/DiscoveryLocatorProperties.java

@ConfigurationProperties("spring.cloud.gateway.discovery.locator")
public class DiscoveryLocatorProperties {

	/** Flag that enables DiscoveryClient gateway integration */
	private boolean enabled = false;

	/**
	 * The prefix for the routeId, defaults to discoveryClient.getClass().getSimpleName() + "_".
	 * Service Id will be appended to create the routeId.
	 */
	private String routeIdPrefix;

	/**
	 * SpEL expression that will evaluate whether to include a service in gateway integration or not,
	 * defaults to: true
	 */
	private String includeExpression = "true";

	/** SpEL expression that create the uri for each route, defaults to: 'lb://'+serviceId */
	private String urlExpression = "'lb://'+serviceId";

	/**
	 * Option to lower case serviceId in predicates and filters, defaults to false.
	 * Useful with eureka when it automatically uppercases serviceId.
	 * so MYSERIVCE, would match /myservice/**
	 */
	private boolean lowerCaseServiceId = false;

	private List<PredicateDefinition> predicates = new ArrayList<>();

	private List<FilterDefinition> filters = new ArrayList<>();

	//......

	@Override
	public String toString() {
		return new ToStringCreator(this)
				.append("enabled", enabled)
				.append("routeIdPrefix", routeIdPrefix)
				.append("includeExpression", includeExpression)
				.append("urlExpression", urlExpression)
				.append("lowerCaseServiceId", lowerCaseServiceId)
				.append("predicates", predicates)
				.append("filters", filters)
				.toString();
	}
}
复制代码

• 默认lowerCaseServiceId为false，因为eureka默认把serviceId大写
• urlExpression默认为'lb://'+serviceId

DiscoveryClientRouteDefinitionLocator

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/discovery/DiscoveryClientRouteDefinitionLocator.java

public class DiscoveryClientRouteDefinitionLocator implements RouteDefinitionLocator {

	private final DiscoveryClient discoveryClient;
	private final DiscoveryLocatorProperties properties;
	private final String routeIdPrefix;

	public DiscoveryClientRouteDefinitionLocator(DiscoveryClient discoveryClient, DiscoveryLocatorProperties properties) {
		this.discoveryClient = discoveryClient;
		this.properties = properties;
		if (StringUtils.hasText(properties.getRouteIdPrefix())) {
			this.routeIdPrefix = properties.getRouteIdPrefix();
		} else {
			this.routeIdPrefix = this.discoveryClient.getClass().getSimpleName() + "_";
		}
	}

	@Override
	public Flux<RouteDefinition> getRouteDefinitions() {
		SimpleEvaluationContext evalCtxt = SimpleEvaluationContext
				.forReadOnlyDataBinding()
				.withInstanceMethods()
				.build();

		SpelExpressionParser parser = new SpelExpressionParser();
		Expression includeExpr = parser.parseExpression(properties.getIncludeExpression());
		Expression urlExpr = parser.parseExpression(properties.getUrlExpression());

		return Flux.fromIterable(discoveryClient.getServices())
				.map(discoveryClient::getInstances)
				.filter(instances -> !instances.isEmpty())
				.map(instances -> instances.get(0))
				.filter(instance -> {
					Boolean include = includeExpr.getValue(evalCtxt, instance, Boolean.class);
					if (include == null) {
						return false;
					}
					return include;
				})
				.map(instance -> {
					String serviceId = instance.getServiceId();

                    RouteDefinition routeDefinition = new RouteDefinition();
                    routeDefinition.setId(this.routeIdPrefix + serviceId);
					String uri = urlExpr.getValue(evalCtxt, instance, String.class);
					routeDefinition.setUri(URI.create(uri));

					final ServiceInstance instanceForEval = new DelegatingServiceInstance(instance, properties);

					for (PredicateDefinition original : this.properties.getPredicates()) {
						PredicateDefinition predicate = new PredicateDefinition();
						predicate.setName(original.getName());
						for (Map.Entry<String, String> entry : original.getArgs().entrySet()) {
							String value = getValueFromExpr(evalCtxt, parser, instanceForEval, entry);
							predicate.addArg(entry.getKey(), value);
						}
						routeDefinition.getPredicates().add(predicate);
					}

                    for (FilterDefinition original : this.properties.getFilters()) {
                    	FilterDefinition filter = new FilterDefinition();
                    	filter.setName(original.getName());
						for (Map.Entry<String, String> entry : original.getArgs().entrySet()) {
							String value = getValueFromExpr(evalCtxt, parser, instanceForEval, entry);
							filter.addArg(entry.getKey(), value);
						}
						routeDefinition.getFilters().add(filter);
					}

                    return routeDefinition;
				});
	}

	String getValueFromExpr(SimpleEvaluationContext evalCtxt, SpelExpressionParser parser, ServiceInstance instance, Map.Entry<String, String> entry) {
		Expression valueExpr = parser.parseExpression(entry.getValue());
		return valueExpr.getValue(evalCtxt, instance, String.class);
	}
	//......
}
复制代码

可以看到这里从discoveryClient.getServices()获取注册信息转换为RouteDefinition

小结

RouteDefinitionLocator接口有不同的实现类：

• InMemoryRouteDefinitionRepository
• CompositeRouteDefinitionLocator
• DiscoveryClientRouteDefinitionLocator
• PropertiesRouteDefinitionLocator
• CachingRouteDefinitionLocator

如果开启spring.cloud.gateway.discovery.locator.enabled=true，那么最后CompositeRouteDefinitionLocator则是组合了InMemoryRouteDefinitionRepository、PropertiesRouteDefinitionLocator、DiscoveryClientRouteDefinitionLocator三个RouteDefinitionLocator

doc

• 114.2 DiscoveryClient Route Definition Locator