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。
java
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 {
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
// 分配空的DataBuffer
DataBuffer 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()) {
@Override
public 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。
java
// 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:off
return 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 DataBuffer
DataBuffer 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));
}
总结
通过上述方式,可以获取到完整的请求和响应报文大小。根据压测结果,此方法对性能无影响。