思路

根據eureka的metadata進行自定義元數據，然後使用ribbon對該元數據進行過濾和匹配，選擇server。

實現

這裏使用header來傳遞路由信息，改造ribbon-discovery-filter-spring-cloud-starter，使其不影響靜態server list。

filter

public class TagFilter extends ZuulFilter {

    private static final Logger LOGGER = LoggerFactory.getLogger(TagFilter.class);

    @Override
    
 
public String filterType() {
        return "pre";
    }

    @Override
    public int filterOrder() {
        return 7;
    }

    @Override
    public boolean shouldFilter() {
        return true;
    }

    @Override
    public 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{

    @Override
    
 
public 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 {

    @Override
    public 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();
    }
}

• Spring Cloud: Ribbon dynamic routing

• SpringCloud Ribbon 降級、限流、灰度發布

springcloud基於ribbon的canary路由方案