Spring Gateway - only requests to the gateway generates spans

[florenciazabala]

Describe the bug

As is explained in this issue I've tried to use manual auto-implementation in a Spring Cloud Gateway API, when a request is made to the Gateway a span is generated correctly but I expect the requests to downstream services also generates a span.

Steps to reproduce

1- Add the following dependencies

 <dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-gateway</artifactId>
        <version>4.1.1</version>
    </dependency>
    <dependency>
        <groupId>io.opentelemetry.instrumentation</groupId>
        <artifactId>opentelemetry-spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>io.opentelemetry.instrumentation</groupId>
        <artifactId>opentelemetry-spring-webflux-5.3</artifactId>
    </dependency>
</dependencies>
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-bom</artifactId>
            <version>1.34.1</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
        <dependency>
            <groupId>io.opentelemetry.instrumentation</groupId>
            <artifactId>opentelemetry-instrumentation-bom-alpha</artifactId>
            <version>2.0.0-alpha</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

2- Add the next code:

  @Bean
    WebFilter telemetryFilter(OpenTelemetry openTelemetry) {
        return SpringWebfluxTelemetry.builder(openTelemetry)
                .build()
                .createWebFilterAndRegisterReactorHook();
    }

Here is a basic example: https://github.com/florenciazabala/otel-spring-gateway

Expected behavior

All requests should generate spans. I expect at least the request to the gateway api and the request to de core api generates spans.

Actual behavior

Only requests to the gateway generate a span.

Javaagent or library instrumentation version

opentelemetry-spring-boot-starter v2.0.0-alpha

Environment

JDK: 21

Additional context

No response

[laurit]

We'd welcome a contribution for this

[trask]

cc @jeanbisutti @zeitlinger

[123liuziming]

Could you please assign it to me?

[123liuziming]

I 've tried 2 ways to solve this problem.

1. Use micrometer-tracing in Reactor Netty to add client span for Spring Cloud Gateway's HttpClient.
2. Enhance each reactor.netty.http.client.HttpClient bean in Spring Context.
   But I found that there are problems with both approaches.

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 * Licensed under the Apache License, Version 2.0 (the "License");
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package org.springframework.cloud.gateway.filter;

import java.net.URI;
import java.time.Duration;
import java.util.List;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelOption;
import io.netty.handler.codec.http.DefaultHttpHeaders;
import io.netty.handler.codec.http.HttpMethod;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.netty.http.client.HttpClient;
import reactor.netty.http.client.HttpClientResponse;

import org.springframework.beans.factory.ObjectProvider;
import org.springframework.cloud.gateway.config.HttpClientProperties;
import org.springframework.cloud.gateway.filter.headers.HttpHeadersFilter;
import org.springframework.cloud.gateway.filter.headers.HttpHeadersFilter.Type;
import org.springframework.cloud.gateway.route.Route;
import org.springframework.cloud.gateway.support.TimeoutException;
import org.springframework.core.Ordered;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DefaultDataBuffer;
import org.springframework.core.io.buffer.NettyDataBuffer;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.server.reactive.AbstractServerHttpResponse;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.http.server.reactive.ServerHttpResponseDecorator;
import org.springframework.util.StringUtils;
import org.springframework.web.server.ResponseStatusException;
import org.springframework.web.server.ServerWebExchange;

import static org.springframework.cloud.gateway.filter.headers.HttpHeadersFilter.filterRequest;
import static org.springframework.cloud.gateway.support.RouteMetadataUtils.CONNECT_TIMEOUT_ATTR;
import static org.springframework.cloud.gateway.support.RouteMetadataUtils.RESPONSE_TIMEOUT_ATTR;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.CLIENT_RESPONSE_CONN_ATTR;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.CLIENT_RESPONSE_HEADER_NAMES;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.ORIGINAL_RESPONSE_CONTENT_TYPE_ATTR;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.PRESERVE_HOST_HEADER_ATTRIBUTE;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.isAlreadyRouted;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.setAlreadyRouted;

/**
 * @author Spencer Gibb
 * @author Biju Kunjummen
 */
public class NettyRoutingFilter implements GlobalFilter, Ordered {

	private static final Log log = LogFactory.getLog(NettyRoutingFilter.class);

	private final HttpClient httpClient;

	private final ObjectProvider<List<HttpHeadersFilter>> headersFiltersProvider;

	private final HttpClientProperties properties;

	// do not use this headersFilters directly, use getHeadersFilters() instead.
	private volatile List<HttpHeadersFilter> headersFilters;

	public NettyRoutingFilter(HttpClient httpClient, ObjectProvider<List<HttpHeadersFilter>> headersFiltersProvider,
			HttpClientProperties properties) {
		this.httpClient = httpClient;
		this.headersFiltersProvider = headersFiltersProvider;
		this.properties = properties;
	}

	public List<HttpHeadersFilter> getHeadersFilters() {
		if (headersFilters == null) {
			headersFilters = headersFiltersProvider.getIfAvailable();
		}
		return headersFilters;
	}

	@Override
	public int getOrder() {
		return Ordered.LOWEST_PRECEDENCE;
	}

	@Override
	@SuppressWarnings("Duplicates")
	public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
		URI requestUrl = exchange.getRequiredAttribute(GATEWAY_REQUEST_URL_ATTR);

		String scheme = requestUrl.getScheme();
		if (isAlreadyRouted(exchange) || (!"http".equals(scheme) && !"https".equals(scheme))) {
			return chain.filter(exchange);
		}
		setAlreadyRouted(exchange);

		ServerHttpRequest request = exchange.getRequest();

		final HttpMethod method = HttpMethod.valueOf(request.getMethodValue());
		final String url = requestUrl.toASCIIString();

		HttpHeaders filtered = filterRequest(getHeadersFilters(), exchange);

		final DefaultHttpHeaders httpHeaders = new DefaultHttpHeaders();
		filtered.forEach(httpHeaders::set);

		boolean preserveHost = exchange.getAttributeOrDefault(PRESERVE_HOST_HEADER_ATTRIBUTE, false);
		Route route = exchange.getAttribute(GATEWAY_ROUTE_ATTR);

		Flux<HttpClientResponse> responseFlux = getHttpClient(route, exchange).headers(headers -> {
			headers.add(httpHeaders);
			// Will either be set below, or later by Netty
			headers.remove(HttpHeaders.HOST);
			if (preserveHost) {
				String host = request.getHeaders().getFirst(HttpHeaders.HOST);
				headers.add(HttpHeaders.HOST, host);
			}
		}).request(method).uri(url).send((req, nettyOutbound) -> {
			if (log.isTraceEnabled()) {
				nettyOutbound.withConnection(connection -> log.trace("outbound route: "
						+ connection.channel().id().asShortText() + ", inbound: " + exchange.getLogPrefix()));
			}
			return nettyOutbound.send(request.getBody().map(this::getByteBuf));
		}).responseConnection((res, connection) -> {

			// Defer committing the response until all route filters have run
			// Put client response as ServerWebExchange attribute and write
			// response later NettyWriteResponseFilter
			exchange.getAttributes().put(CLIENT_RESPONSE_ATTR, res);
			exchange.getAttributes().put(CLIENT_RESPONSE_CONN_ATTR, connection);

			ServerHttpResponse response = exchange.getResponse();
			// put headers and status so filters can modify the response
			HttpHeaders headers = new HttpHeaders();

			res.responseHeaders().forEach(entry -> headers.add(entry.getKey(), entry.getValue()));

			String contentTypeValue = headers.getFirst(HttpHeaders.CONTENT_TYPE);
			if (StringUtils.hasLength(contentTypeValue)) {
				exchange.getAttributes().put(ORIGINAL_RESPONSE_CONTENT_TYPE_ATTR, contentTypeValue);
			}

			setResponseStatus(res, response);

			// make sure headers filters run after setting status so it is
			// available in response
			HttpHeaders filteredResponseHeaders = HttpHeadersFilter.filter(getHeadersFilters(), headers, exchange,
					Type.RESPONSE);

			if (!filteredResponseHeaders.containsKey(HttpHeaders.TRANSFER_ENCODING)
					&& filteredResponseHeaders.containsKey(HttpHeaders.CONTENT_LENGTH)) {
				// It is not valid to have both the transfer-encoding header and
				// the content-length header.
				// Remove the transfer-encoding header in the response if the
				// content-length header is present.
				response.getHeaders().remove(HttpHeaders.TRANSFER_ENCODING);
			}

			exchange.getAttributes().put(CLIENT_RESPONSE_HEADER_NAMES, filteredResponseHeaders.keySet());

			response.getHeaders().putAll(filteredResponseHeaders);

			return Mono.just(res);
		});

		Duration responseTimeout = getResponseTimeout(route);
		if (responseTimeout != null) {
			responseFlux = responseFlux
					.timeout(responseTimeout,
							Mono.error(new TimeoutException("Response took longer than timeout: " + responseTimeout)))
					.onErrorMap(TimeoutException.class,
							th -> new ResponseStatusException(HttpStatus.GATEWAY_TIMEOUT, th.getMessage(), th));
		}

		return responseFlux.then(chain.filter(exchange));
	}

	protected ByteBuf getByteBuf(DataBuffer dataBuffer) {
		if (dataBuffer instanceof NettyDataBuffer) {
			NettyDataBuffer buffer = (NettyDataBuffer) dataBuffer;
			return buffer.getNativeBuffer();
		}
		// MockServerHttpResponse creates these
		else if (dataBuffer instanceof DefaultDataBuffer) {
			DefaultDataBuffer buffer = (DefaultDataBuffer) dataBuffer;
			return Unpooled.wrappedBuffer(buffer.getNativeBuffer());
		}
		throw new IllegalArgumentException("Unable to handle DataBuffer of type " + dataBuffer.getClass());
	}

	private void setResponseStatus(HttpClientResponse clientResponse, ServerHttpResponse response) {
		HttpStatus status = HttpStatus.resolve(clientResponse.status().code());
		if (status != null) {
			response.setStatusCode(status);
		}
		else {
			while (response instanceof ServerHttpResponseDecorator) {
				response = ((ServerHttpResponseDecorator) response).getDelegate();
			}
			if (response instanceof AbstractServerHttpResponse) {
				((AbstractServerHttpResponse) response).setStatusCodeValue(clientResponse.status().code());
			}
			else {
				// TODO: log warning here, not throw error?
				throw new IllegalStateException("Unable to set status code " + clientResponse.status().code()
						+ " on response of type " + response.getClass().getName());
			}
		}
	}

	/**
	 * Creates a new HttpClient with per route timeout configuration. Sub-classes that
	 * override, should call super.getHttpClient() if they want to honor the per route
	 * timeout configuration.
	 * @param route the current route.
	 * @param exchange the current ServerWebExchange.
	 * @param chain the current GatewayFilterChain.
	 * @return
	 */
	protected HttpClient getHttpClient(Route route, ServerWebExchange exchange) {
		Object connectTimeoutAttr = route.getMetadata().get(CONNECT_TIMEOUT_ATTR);
		if (connectTimeoutAttr != null) {
			Integer connectTimeout = getInteger(connectTimeoutAttr);
			return this.httpClient.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, connectTimeout);
		}
		return httpClient;
	}

	static Integer getInteger(Object connectTimeoutAttr) {
		Integer connectTimeout;
		if (connectTimeoutAttr instanceof Integer) {
			connectTimeout = (Integer) connectTimeoutAttr;
		}
		else {
			connectTimeout = Integer.parseInt(connectTimeoutAttr.toString());
		}
		return connectTimeout;
	}

	private Duration getResponseTimeout(Route route) {
		Object responseTimeoutAttr = route.getMetadata().get(RESPONSE_TIMEOUT_ATTR);
		Long responseTimeout = null;
		if (responseTimeoutAttr != null) {
			if (responseTimeoutAttr instanceof Number) {
				responseTimeout = ((Number) responseTimeoutAttr).longValue();
			}
			else {
				responseTimeout = Long.valueOf(responseTimeoutAttr.toString());
			}
		}
		return responseTimeout != null ? Duration.ofMillis(responseTimeout) : properties.getResponseTimeout();
	}

}

We should instrument the HttpClient after the gateway invoke responseConnection, which is hard for a library instrumentation. Does anybody have a good solution?