SpringCloudGateway获取报文大小

Overview

SpringCloud Gateway使用过程中，希望获取报文大小。由于SpringCloud Gateway底层基于Netty实现，直接读取报文，会大幅影响网关性能。因此本文将通过其他方式获取报文大小。本文基于2.2.9 SpringCloud Gateway开发。

读取请求报文大小

实现自定义Filter，读取请求报文大小，具体可参考以下代码。

import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpRequestDecorator;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;@Slf4j
@Component
public class ReadRequestBodyFilter implements GlobalFilter {@Overridepublic Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {// 分配空的DataBufferDataBuffer emptyBuffer = exchange.getResponse().bufferFactory().allocateBuffer(0);// 使用 DataBufferUtils.join 将DataBuffer数据流聚合为一个Mono// 聚合后的 DataBuffer 为一个完整报文的 DataBuffer。// 如果请求报文为空，使用分配的空 DataBuffer。return DataBufferUtils.join(exchange.getRequest().getBody().defaultIfEmpty(emptyBuffer)).flatMap(dataBuffer -> {// 获取报文大小，不直接获取报文内容。int size = dataBuffer.readableByteCount();log.info("=====> request body size: {}", size);if (size == 0) {// 如果报文内容为空，需要主动释放创建的空的DataBuffer。DataBufferUtils.release(dataBuffer);return chain.filter(exchange);}// 复制一份DataBuffer，slice方法不会retain DataBuffer，只是复制的指针坐标。Flux<DataBuffer> cachedFlux = Flux.defer(() -> Flux.just(dataBuffer.slice(0, dataBuffer.readableByteCount())));// 构建新的 Request，重写 getBody 返回复制的报文ServerHttpRequest mutatedRequest = new ServerHttpRequestDecorator(exchange.getRequest()) {@Overridepublic Flux<DataBuffer> getBody() {return cachedFlux;}};// 继续处理请求return chain.filter(exchange.mutate().request(mutatedRequest).build());});}
}

读取响应报文大小

重写NettyWriteResponseFilter，实现响应报文大小获取。此方法有点不够优雅。

// 重写 filter 方法
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {// NOTICE: nothing in "pre" filter stage as CLIENT_RESPONSE_CONN_ATTR is not added// until the NettyRoutingFilter is run// @formatter:offreturn chain.filter(exchange).doOnError(throwable -> cleanup(exchange)).then(Mono.defer(() -> {Connection connection = exchange.getAttribute(CLIENT_RESPONSE_CONN_ATTR);if (connection == null) {return Mono.empty();}if (log.isTraceEnabled()) {log.trace("NettyWriteResponseFilter start inbound: "+ connection.channel().id().asShortText() + ", outbound: "+ exchange.getLogPrefix());}ServerHttpResponse response = exchange.getResponse();// TODO: needed?final Flux<DataBuffer> body = connection.inbound().receive().retain().map(byteBuf -> wrap(byteBuf, response));MediaType contentType = null;try {contentType = response.getHeaders().getContentType();} catch (Exception e) {if (log.isTraceEnabled()) {log.trace("invalid media type", e);}}// 重写部分代码，如果为 stream 类型报文，则忽略报文读取// stream media type, we can not join databuffer, just ignore body size.if (isStreamingMediaType(contentType)) {return response.writeAndFlushWith(body.map(Flux::just));}// 分配空的 DataBufferDataBuffer emptyBuffer = exchange.getResponse().bufferFactory().allocateBuffer(0);// 聚合 DataBuffer 构建大的 DataBuffer 包含完整报文return DataBufferUtils.join(body.defaultIfEmpty(emptyBuffer)).flatMap(dataBuffer -> {// 读取报文大小int size = dataBuffer.readableByteCount();log.info("=====> response body size: " + size);// 复制 DataBuffer Flux<DataBuffer> cachedFlux = Flux.defer(() -> Flux.just(dataBuffer.slice(0, size)));// 向 response 写入数据return response.writeWith(cachedFlux);});})).doOnCancel(() -> cleanup(exchange));
}