SpringCloud 微服务中网关如何记录请求响应日志？

在基于SpringCloud开发的微服务中，我们一般会选择在网关层记录请求和响应日志，并将其收集到ELK中用作查询和分析。

今天我们就来看看如何实现此功能。

日志实体类

首先我们在网关中定义一个日志实体，用于组装日志对象

@Data
public class AccessLog {

    /**用户编号**/
    private Long userId;

    /**路由**/
    private String targetServer;

    /**协议**/
    private String schema;
    
    /**请求方法名**/
    private String requestMethod;
    
    /**访问地址**/
    private String requestUrl;

    /**请求IP**/
    private String clientIp;

    /**查询参数**/
    private MultiValueMap<String, String> queryParams;
    
    /**请求体**/
    private String requestBody;
    
    /**请求头**/
    private MultiValueMap<String, String> requestHeaders;

     /**响应体**/
    private String responseBody;
    
    /**响应头**/
    private MultiValueMap<String, String> responseHeaders;
    
     /**响应结果**/
    private HttpStatusCode httpStatusCode;
    
     /**开始请求时间**/
    private LocalDateTime startTime;
    
    /**结束请求时间**/
    private LocalDateTime endTime;
    
    /**执行时长，单位：毫秒**/
    private Integer duration;

}

网关日志过滤器

接下来我们在网关中定义一个Filter，用于收集日志信息。

@Component
public class AccessLogFilter implements GlobalFilter, Ordered {

    private final List<HttpMessageReader<?>> messageReaders = HandlerStrategies.withDefaults().messageReaders();

    /**
     * 打印日志
     * @param accessLog 网关日志
     */
    private void writeAccessLog(AccessLog accessLog) {
        log.info("----access---- : {}", JsonUtils.obj2StringPretty(accessLog));
    }

    /**
     * 顺序必须是<-1，否则标准的NettyWriteResponseFilter将在您的过滤器得到一个被调用的机会之前发送响应
     * 也就是说如果不小于 -1 ，将不会执行获取后端响应的逻辑
     * @return
     */
    @Override
    public int getOrder() {
        return -100;
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        // 将 Request 中可以直接获取到的参数，设置到网关日志
        ServerHttpRequest request = exchange.getRequest();

        AccessLog gatewayLog = new AccessLog();
        gatewayLog.setTargetServer(WebUtils.getGatewayRoute(exchange).getId());
        gatewayLog.setSchema(request.getURI().getScheme());
        gatewayLog.setRequestMethod(request.getMethod().name());
        gatewayLog.setRequestUrl(request.getURI().getRawPath());
        gatewayLog.setQueryParams(request.getQueryParams());
        gatewayLog.setRequestHeaders(request.getHeaders());
        gatewayLog.setStartTime(LocalDateTime.now());
        gatewayLog.setClientIp(WebUtils.getClientIP(exchange));

        // 继续 filter 过滤
        MediaType mediaType = request.getHeaders().getContentType();
        if (MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(mediaType)
                || MediaType.APPLICATION_JSON.isCompatibleWith(mediaType)) { // 适合 JSON 和 Form 提交的请求
            return filterWithRequestBody(exchange, chain, gatewayLog);
        }
        return filterWithoutRequestBody(exchange, chain, gatewayLog);
    }


    /**
     * 没有请求体的请求只需要记录日志
     */
    private Mono<Void> filterWithoutRequestBody(ServerWebExchange exchange, GatewayFilterChain chain, AccessLog accessLog) {
        // 包装 Response，用于记录 Response Body
        ServerHttpResponseDecorator decoratedResponse = recordResponseLog(exchange, accessLog);

        return chain.filter(exchange.mutate().response(decoratedResponse).build())
                .then(Mono.fromRunnable(() -> writeAccessLog(accessLog)));
    }

    /**
     * 需要读取请求体
     * 参考 {@link ModifyRequestBodyGatewayFilterFactory} 实现
     */
    private Mono<Void> filterWithRequestBody(ServerWebExchange exchange, GatewayFilterChain chain, AccessLog gatewayLog) {
        // 设置 Request Body 读取时，设置到网关日志
        ServerRequest serverRequest = ServerRequest.create(exchange, messageReaders);

        Mono<String> modifiedBody = serverRequest.bodyToMono(String.class).flatMap(body -> {
            gatewayLog.setRequestBody(body);
            return Mono.just(body);
        });

        // 通过 BodyInserter 插入 body(支持修改body), 避免 request body 只能获取一次
        BodyInserter<Mono<String>, ReactiveHttpOutputMessage> bodyInserter = BodyInserters.fromPublisher(modifiedBody, String.class);
        HttpHeaders headers = new HttpHeaders();
        headers.putAll(exchange.getRequest().getHeaders());
        // the new content type will be computed by bodyInserter
        // and then set in the request decorator
        headers.remove(HttpHeaders.CONTENT_LENGTH);

        CachedBodyOutputMessage outputMessage = new CachedBodyOutputMessage(exchange, headers);

        // 通过 BodyInserter 将 Request Body 写入到 CachedBodyOutputMessage 中
        return bodyInserter.insert(outputMessage, new BodyInserterContext()).then(Mono.defer(() -> {
            // 重新封装请求
            ServerHttpRequest decoratedRequest = requestDecorate(exchange, headers, outputMessage);
            // 记录响应日志
            ServerHttpResponseDecorator decoratedResponse = recordResponseLog(exchange, gatewayLog);
            // 记录普通的
            return chain.filter(exchange.mutate().request(decoratedRequest).response(decoratedResponse).build())
                    .then(Mono.fromRunnable(() -> writeAccessLog(gatewayLog))); // 打印日志

        }));
    }

    /**
     * 记录响应日志
     * 通过 DataBufferFactory 解决响应体分段传输问题。
     */
    private ServerHttpResponseDecorator recordResponseLog(ServerWebExchange exchange, AccessLog accessLog) {
        ServerHttpResponse response = exchange.getResponse();

        return new ServerHttpResponseDecorator(response) {

            @Override
            public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
                if (body instanceof Flux) {
                    DataBufferFactory bufferFactory = response.bufferFactory();
                    // 计算执行时间
                    accessLog.setEndTime(LocalDateTime.now());
                    accessLog.setDuration((int) (LocalDateTimeUtil.between(accessLog.getStartTime(),
                            accessLog.getEndTime()).toMillis()));
                    accessLog.setResponseHeaders(response.getHeaders());
                    accessLog.setHttpStatusCode(response.getStatusCode());

                    // 获取响应类型，如果是 json 就打印
                    String originalResponseContentType = exchange.getAttribute(ServerWebExchangeUtils.ORIGINAL_RESPONSE_CONTENT_TYPE_ATTR);

                    if (StrUtil.isNotBlank(originalResponseContentType)
                            && originalResponseContentType.contains("application/json")) {
                        Flux<? extends DataBuffer> fluxBody = Flux.from(body);

                        return super.writeWith(fluxBody.buffer().map(dataBuffers -> {
                            // 设置 response body 到网关日志
                            byte[] content = readContent(dataBuffers);
                            String responseResult = new String(content, StandardCharsets.UTF_8);
                            accessLog.setResponseBody(responseResult);

                            // 响应
                            return bufferFactory.wrap(content);
                        }));
                    }
                }
                // if body is not a flux. never got there.
                return super.writeWith(body);
            }
        };
    }


    /**
     * 请求装饰器，支持重新计算 headers、body 缓存
     *
     * @param exchange 请求
     * @param headers 请求头
     * @param outputMessage body 缓存
     * @return 请求装饰器
     */
    private ServerHttpRequestDecorator requestDecorate(ServerWebExchange exchange, HttpHeaders headers, CachedBodyOutputMessage outputMessage) {
        return new ServerHttpRequestDecorator(exchange.getRequest()) {

            @Override
            public HttpHeaders getHeaders() {
                long contentLength = headers.getContentLength();
                HttpHeaders httpHeaders = new HttpHeaders();
                httpHeaders.putAll(super.getHeaders());
                if (contentLength > 0) {
                    httpHeaders.setContentLength(contentLength);
                } else {
                    // TODO: this causes a 'HTTP/1.1 411 Length Required' // on
                    // httpbin.org
                    httpHeaders.set(HttpHeaders.TRANSFER_ENCODING, "chunked");
                }
                return httpHeaders;
            }

            @Override
            public Flux<DataBuffer> getBody() {
                return outputMessage.getBody();
            }
        };
    }

    /**
     * 从dataBuffers中读取数据
     * @author jam
     * @date 2024/5/26 22:31
     */
    private byte[] readContent(List<? extends DataBuffer> dataBuffers) {
        // 合并多个流集合，解决返回体分段传输
        DataBufferFactory dataBufferFactory = new DefaultDataBufferFactory();
        DataBuffer join = dataBufferFactory.join(dataBuffers);
        byte[] content = new byte[join.readableByteCount()];
        join.read(content);
        // 释放掉内存
        DataBufferUtils.release(join);
        return content;
    }

}

代码较长建议直接拷贝到编辑器，只要注意下面一个关键点：

getOrder()方法返回的值必须要<-1，否则标准的NettyWriteResponseFilter将在您的过滤器被调用的机会之前发送响应，即不会执行获取后端响应参数的方法

通过上面的两步我们已经可以获取到请求的输入输出参数了，在 writeAccessLog()中将其打印到日志文件，方便通过ELK进行收集。

在实际项目中，网关日志量一般会非常大，不建议使用数据库进行存储。

实际效果

服务正常响应

服务异常响应