Benchtool: add -bench.write.proxy-url argument. (#223)

This allows configuring the Prometheus remote-write client with a HTTP proxy URL.

Getting the client to support the HTTP[S]_PROXY environment variables is not
straightforward, as the creation of the HTTP transport is deep in the upstream
code. Additionally, the client appears to have it's own mechanism for
configuring a HTTP proxy, so it would be safer to use that without meddling.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 Order should be `CHANGE`, `FEATURE`, `ENHANCEMENT`, and `BUGFIX`
 
+## unreleased
+
+* [ENHANCEMENT] Benchtool: add `-bench.write.proxy-url` argument for configuring the Prometheus remote-write client with a HTTP proxy URL. #223
+
 ## v0.10.6
 
 * [FEATURE] Rules check for Loki now supports `pattern`.

pkg/bench/write_runner.go

@@ -29,13 +29,15 @@ type WriteBenchConfig struct {
 	Endpoint          string `yaml:"endpoint"`
 	BasicAuthUsername string `yaml:"basic_auth_username"`
 	BasicAuthPasword  string `yaml:"basic_auth_password"`
+	ProxyURL          string `yaml:"proxy_url"`
 }
 
 func (cfg *WriteBenchConfig) RegisterFlags(f *flag.FlagSet) {
 	f.BoolVar(&cfg.Enabled, "bench.write.enabled", false, "enable write benchmarking")
 	f.StringVar(&cfg.Endpoint, "bench.write.endpoint", "", "Remote write endpoint.")
 	f.StringVar(&cfg.BasicAuthUsername, "bench.write.basic-auth-username", "", "Set the basic auth username on remote write requests.")
 	f.StringVar(&cfg.BasicAuthPasword, "bench.write.basic-auth-password", "", "Set the basic auth password on remote write requests.")
+	f.StringVar(&cfg.ProxyURL, "bench.write.proxy-url", "", "Set the HTTP proxy URL to use on remote write requests.")
 }
 
 type WriteBenchmarkRunner struct {
@@ -110,6 +112,15 @@ func (w *WriteBenchmarkRunner) getRandomWriteClient() (*writeClient, error) {
 		if err != nil {
 			return nil, err
 		}
+
+		var proxyURL *url.URL
+		if w.cfg.ProxyURL != "" {
+			proxyURL, err = url.Parse(w.cfg.ProxyURL)
+			if err != nil {
+				return nil, errors.Wrap(err, "invalid proxy url")
+			}
+		}
+
 		cli, err = newWriteClient("bench-"+pick, w.tenantName, &remote.ClientConfig{
 			URL:     &config.URL{URL: u},
 			Timeout: model.Duration(w.workload.options.Timeout),
@@ -119,6 +130,9 @@ func (w *WriteBenchmarkRunner) getRandomWriteClient() (*writeClient, error) {
 					Username: w.cfg.BasicAuthUsername,
 					Password: config.Secret(w.cfg.BasicAuthPasword),
 				},
+				ProxyURL: config.URL{
+					URL: proxyURL,
+				},
 			},
 		}, w.logger, w.requestDuration)
 		if err != nil {