package com.iailab.gateway.filter.grey;
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import lombok.AllArgsConstructor;
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import lombok.extern.slf4j.Slf4j;
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import org.springframework.cloud.client.ServiceInstance;
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import org.springframework.cloud.client.loadbalancer.*;
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import org.springframework.cloud.gateway.config.GatewayLoadBalancerProperties;
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import org.springframework.cloud.gateway.filter.GatewayFilterChain;
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import org.springframework.cloud.gateway.filter.GlobalFilter;
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import org.springframework.cloud.gateway.filter.ReactiveLoadBalancerClientFilter;
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import org.springframework.cloud.gateway.support.DelegatingServiceInstance;
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import org.springframework.cloud.gateway.support.NotFoundException;
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import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
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import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
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import org.springframework.core.Ordered;
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import org.springframework.stereotype.Component;
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import org.springframework.web.server.ServerWebExchange;
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import reactor.core.publisher.Mono;
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import java.net.URI;
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import java.util.Map;
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import java.util.Set;
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import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.*;
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/**
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* 支持灰度功能的 {@link ReactiveLoadBalancerClientFilter} 实现类
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*
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* 由于 {@link ReactiveLoadBalancerClientFilter#choose(Request, String, Set)} 是 private 方法，无法进行重写。
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* 因此，这里只好 copy 它所有的代码，手动重写 choose 方法
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*
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* 具体的使用与实现原理，可阅读如下两个文章：
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* 1. https://www.jianshu.com/p/6db15bc0be8f
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* 2. https://cloud.tencent.com/developer/article/1620795
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*
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* @author iailab
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*/
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@Component
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@AllArgsConstructor
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@Slf4j
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@SuppressWarnings({"JavadocReference", "rawtypes", "unchecked", "ConstantConditions"})
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public class GrayReactiveLoadBalancerClientFilter implements GlobalFilter, Ordered {
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private final LoadBalancerClientFactory clientFactory;
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private final GatewayLoadBalancerProperties properties;
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@Override
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public int getOrder() {
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return ReactiveLoadBalancerClientFilter.LOAD_BALANCER_CLIENT_FILTER_ORDER;
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}
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@Override
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public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
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URI url = exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR);
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String schemePrefix = exchange.getAttribute(GATEWAY_SCHEME_PREFIX_ATTR);
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// 修改 by iailab：将 lb 替换成 grayLb，表示灰度负载均衡
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if (url == null || (!"grayLb".equals(url.getScheme()) && !"grayLb".equals(schemePrefix))) {
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return chain.filter(exchange);
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}
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// preserve the original url
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addOriginalRequestUrl(exchange, url);
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if (log.isTraceEnabled()) {
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log.trace(ReactiveLoadBalancerClientFilter.class.getSimpleName() + " url before: " + url);
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}
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URI requestUri = exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR);
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String serviceId = requestUri.getHost();
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Set<LoadBalancerLifecycle> supportedLifecycleProcessors = LoadBalancerLifecycleValidator
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.getSupportedLifecycleProcessors(clientFactory.getInstances(serviceId, LoadBalancerLifecycle.class),
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RequestDataContext.class, ResponseData.class, ServiceInstance.class);
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DefaultRequest<RequestDataContext> lbRequest = new DefaultRequest<>(
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new RequestDataContext(new RequestData(exchange.getRequest()), getHint(serviceId)));
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return choose(lbRequest, serviceId, supportedLifecycleProcessors).doOnNext(response -> {
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if (!response.hasServer()) {
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supportedLifecycleProcessors.forEach(lifecycle -> lifecycle
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.onComplete(new CompletionContext<>(CompletionContext.Status.DISCARD, lbRequest, response)));
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throw NotFoundException.create(properties.isUse404(), "Unable to find instance for " + url.getHost());
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}
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ServiceInstance retrievedInstance = response.getServer();
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URI uri = exchange.getRequest().getURI();
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// if the `lb:<scheme>` mechanism was used, use `<scheme>` as the default,
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// if the loadbalancer doesn't provide one.
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String overrideScheme = retrievedInstance.isSecure() ? "https" : "http";
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if (schemePrefix != null) {
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overrideScheme = url.getScheme();
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}
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DelegatingServiceInstance serviceInstance = new DelegatingServiceInstance(retrievedInstance,
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overrideScheme);
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URI requestUrl = reconstructURI(serviceInstance, uri);
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if (log.isTraceEnabled()) {
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log.trace("LoadBalancerClientFilter url chosen: " + requestUrl);
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}
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exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl);
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exchange.getAttributes().put(GATEWAY_LOADBALANCER_RESPONSE_ATTR, response);
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supportedLifecycleProcessors.forEach(lifecycle -> lifecycle.onStartRequest(lbRequest, response));
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}).then(chain.filter(exchange))
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.doOnError(throwable -> supportedLifecycleProcessors.forEach(lifecycle -> lifecycle
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.onComplete(new CompletionContext<ResponseData, ServiceInstance, RequestDataContext>(
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CompletionContext.Status.FAILED, throwable, lbRequest,
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exchange.getAttribute(GATEWAY_LOADBALANCER_RESPONSE_ATTR)))))
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.doOnSuccess(aVoid -> supportedLifecycleProcessors.forEach(lifecycle -> lifecycle
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.onComplete(new CompletionContext<ResponseData, ServiceInstance, RequestDataContext>(
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CompletionContext.Status.SUCCESS, lbRequest,
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exchange.getAttribute(GATEWAY_LOADBALANCER_RESPONSE_ATTR),
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new ResponseData(exchange.getResponse(), new RequestData(exchange.getRequest()))))));
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}
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protected URI reconstructURI(ServiceInstance serviceInstance, URI original) {
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return LoadBalancerUriTools.reconstructURI(serviceInstance, original);
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}
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private Mono<Response<ServiceInstance>> choose(Request<RequestDataContext> lbRequest, String serviceId,
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Set<LoadBalancerLifecycle> supportedLifecycleProcessors) {
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// 修改 by iailab：直接创建 GrayLoadBalancer 对象
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GrayLoadBalancer loadBalancer = new GrayLoadBalancer(
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clientFactory.getLazyProvider(serviceId, ServiceInstanceListSupplier.class), serviceId);
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supportedLifecycleProcessors.forEach(lifecycle -> lifecycle.onStart(lbRequest));
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return loadBalancer.choose(lbRequest);
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}
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private String getHint(String serviceId) {
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LoadBalancerProperties loadBalancerProperties = clientFactory.getProperties(serviceId);
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Map<String, String> hints = loadBalancerProperties.getHint();
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String defaultHint = hints.getOrDefault("default", "default");
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String hintPropertyValue = hints.get(serviceId);
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return hintPropertyValue != null ? hintPropertyValue : defaultHint;
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}
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}
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