Set timeout for requests made by the EVP proxy

Without this, a request would continue running even after our Server
(which received a request from e.g. a tracer) has already timed out and,
because of this, would not propagate the response of the request anyway.

pkg/trace/api/api.go

@@ -195,6 +195,14 @@ func replyWithVersion(hash string, version string, h http.Handler) http.Handler
 	})
 }
 
+func getConfiguredRequestTimeoutDuration(conf *config.AgentConfig) time.Duration {
+	timeout := 5 * time.Second
+	if conf.ReceiverTimeout > 0 {
+		timeout = time.Duration(conf.ReceiverTimeout) * time.Second
+	}
+	return timeout
+}
+
 // Start starts doing the HTTP server and is ready to receive traces
 func (r *HTTPReceiver) Start() {
 	if r.conf.ReceiverPort == 0 &&
@@ -205,10 +213,7 @@ func (r *HTTPReceiver) Start() {
 		return
 	}
 
-	timeout := 5 * time.Second
-	if r.conf.ReceiverTimeout > 0 {
-		timeout = time.Duration(r.conf.ReceiverTimeout) * time.Second
-	}
+	timeout := getConfiguredRequestTimeoutDuration(r.conf)
 	httpLogger := log.NewThrottled(5, 10*time.Second) // limit to 5 messages every 10 seconds
 	r.server = &http.Server{
 		ReadTimeout:  timeout,

pkg/trace/api/evp_proxy.go

@@ -7,6 +7,7 @@ package api
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"io"
 	stdlog "log"
@@ -174,6 +175,13 @@ func (t *evpProxyTransport) RoundTrip(req *http.Request) (rresp *http.Response,
 		req.Header.Set("DD-APPLICATION-KEY", t.conf.EVPProxy.ApplicationKey)
 	}
 
+	// Timeout: Our outbound request(s) can't take longer than the WriteTimeout of the server
+	timeout := getConfiguredRequestTimeoutDuration(t.conf)
+	deadline := time.Now().Add(timeout)
+	ctx, ctxCancel := context.WithDeadline(req.Context(), deadline)
+	req = req.WithContext(ctx)
+	defer ctxCancel()
+
 	// Set target URL and API key header (per domain)
 	req.URL.Scheme = "https"
 	setTarget := func(r *http.Request, host, apiKey string) {