思路

根据eureka的metadata进行自定义元数据，然后使用ribbon对该元数据进行过滤和匹配，选择server。

实现

这里使用header来传递路由信息，改造ribbon-discovery-filter-spring-cloud-starter，使其不影响静态server list。

filter

public class TagFilter extends ZuulFilter {private static final Logger LOGGER = LoggerFactory.getLogger(TagFilter.class);@Overridepublic String filterType() {return "pre";}@Overridepublic int filterOrder() {return 7;}@Overridepublic boolean shouldFilter() {return true;}@Overridepublic Object run() {RequestContext requestContext = RequestContext.getCurrentContext();HttpServletRequest request = requestContext.getRequest();String tag = request.getHeader("tag");RibbonFilterContextHolder.getCurrentContext().add("tag", tag);LOGGER.info("route {} to {}",request.getRequestURI(),tag);return null;}
}

predicate

public class MetadataAwarePredicate extends AbstractServerPredicate{@Overridepublic boolean apply(PredicateKey input) {if(input == null || !(input.getServer() instanceof DiscoveryEnabledServer)){return true;}DiscoveryEnabledServer server = (DiscoveryEnabledServer) input.getServer();final RibbonFilterContext context = RibbonFilterContextHolder.getCurrentContext();final Set<Map.Entry<String, String>> attributes = Collections.unmodifiableSet(context.getAttributes().entrySet());final Map<String, String> metadata = server.getInstanceInfo().getMetadata();return metadata.entrySet().containsAll(attributes);}
}

rule

public class MetadataAwareRule extends ZoneAvoidanceRule {@Overridepublic AbstractServerPredicate getPredicate() {return new MetadataAwarePredicate();}
}

autoconfig

@Configuration
@ConditionalOnClass(DiscoveryEnabledNIWSServerList.class)
@AutoConfigureBefore(RibbonClientConfiguration.class)
@ConditionalOnProperty(value = "ribbon.filter.metadata.enabled", matchIfMissing = true)
public class RibbonMetaFilterAutoConfiguration {@Bean@ConditionalOnMissingBean@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)public MetadataAwareRule metadataAwareRule() {return new MetadataAwareRule();}
}

doc

• Spring Cloud: Ribbon dynamic routing

• SpringCloud Ribbon 降级、限流、灰度发布

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