http: Add the ability to not follow redirects

Currently, when we unmarshal, we get the default value, which is to
follow redirects.

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

config/http_config.go

@@ -111,6 +111,10 @@ type HTTPClientConfig struct {
 	ProxyURL URL `yaml:"proxy_url,omitempty"`
 	// TLSConfig to use to connect to the targets.
 	TLSConfig TLSConfig `yaml:"tls_config,omitempty"`
+	// FollowRedirects specifies wheter the client should follow the HTTP 3xx redirects.
+	// The omitempty flag is not set, because it would be hidden from the
+	// marshalled configuration when set to false.
+	FollowRedirects bool `yaml:"follow_redirects"`
 }
 
 // SetDirectory joins any relative file paths with dir.
@@ -172,6 +176,9 @@ func (c *HTTPClientConfig) Validate() error {
 // UnmarshalYAML implements the yaml.Unmarshaler interface
 func (c *HTTPClientConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	type plain HTTPClientConfig
+	*c = HTTPClientConfig{
+		FollowRedirects: true,
+	}
 	if err := unmarshal((*plain)(c)); err != nil {
 		return err
 	}
@@ -196,7 +203,13 @@ func NewClientFromConfig(cfg HTTPClientConfig, name string, disableKeepAlives, e
 	if err != nil {
 		return nil, err
 	}
-	return newClient(rt), nil
+	client := newClient(rt)
+	if !cfg.FollowRedirects {
+		client.CheckRedirect = func(*http.Request, []*http.Request) error {
+			return http.ErrUseLastResponse
+		}
+	}
+	return client, nil
 }
 
 // NewRoundTripperFromConfig returns a new HTTP RoundTripper configured for the

config/http_config_test.go

@@ -296,6 +296,44 @@ func TestNewClientFromConfig(t *testing.T) {
 					fmt.Fprint(w, ExpectedMessage)
 				}
 			},
+		}, {
+			clientConfig: HTTPClientConfig{
+				FollowRedirects: true,
+				TLSConfig: TLSConfig{
+					CAFile:             TLSCAChainPath,
+					CertFile:           ClientCertificatePath,
+					KeyFile:            ClientKeyNoPassPath,
+					ServerName:         "",
+					InsecureSkipVerify: false},
+			},
+			handler: func(w http.ResponseWriter, r *http.Request) {
+				switch r.URL.Path {
+				case "/redirected":
+					fmt.Fprintf(w, ExpectedMessage)
+				default:
+					http.Redirect(w, r, "/redirected", http.StatusFound)
+				}
+			},
+		}, {
+			clientConfig: HTTPClientConfig{
+				FollowRedirects: false,
+				TLSConfig: TLSConfig{
+					CAFile:             TLSCAChainPath,
+					CertFile:           ClientCertificatePath,
+					KeyFile:            ClientKeyNoPassPath,
+					ServerName:         "",
+					InsecureSkipVerify: false},
+			},
+			handler: func(w http.ResponseWriter, r *http.Request) {
+				switch r.URL.Path {
+				case "/redirected":
+					fmt.Fprint(w, "The redirection was followed.")
+				default:
+					w.Header()["Content-Type"] = nil
+					http.Redirect(w, r, "/redirected", http.StatusFound)
+					fmt.Fprint(w, ExpectedMessage)
+				}
+			},
 		},
 	}
 
@@ -317,7 +355,7 @@ func TestNewClientFromConfig(t *testing.T) {
 		}
 		response, err := client.Get(testServer.URL)
 		if err != nil {
-			t.Errorf("Can't connect to the test server using this config: %+v", validConfig.clientConfig)
+			t.Errorf("Can't connect to the test server using this config: %+v %v", validConfig.clientConfig, err)
 			continue
 		}
 
@@ -932,6 +970,16 @@ func TestHideHTTPClientConfigSecrets(t *testing.T) {
 	}
 }
 
+func TestDefaultFollowRedirect(t *testing.T) {
+	cfg, _, err := LoadHTTPConfigFile("testdata/http.conf.good.yml")
+	if err != nil {
+		t.Errorf("Error loading HTTP client config: %v", err)
+	}
+	if !cfg.FollowRedirects {
+		t.Errorf("follow_redirects should be true")
+	}
+}
+
 func TestValidateHTTPConfig(t *testing.T) {
 	cfg, _, err := LoadHTTPConfigFile("testdata/http.conf.good.yml")
 	if err != nil {