Support custom headers when fetching configuration through HTTP

pkg/provider/http/http.go

@@ -24,10 +24,12 @@ var _ provider.Provider = (*Provider)(nil)
 
 // Provider is a provider.Provider implementation that queries an HTTP(s) endpoint for a configuration.
 type Provider struct {
-	Endpoint              string           `description:"Load configuration from this endpoint." json:"endpoint" toml:"endpoint" yaml:"endpoint"`
-	PollInterval          ptypes.Duration  `description:"Polling interval for endpoint." json:"pollInterval,omitempty" toml:"pollInterval,omitempty" yaml:"pollInterval,omitempty" export:"true"`
-	PollTimeout           ptypes.Duration  `description:"Polling timeout for endpoint." json:"pollTimeout,omitempty" toml:"pollTimeout,omitempty" yaml:"pollTimeout,omitempty" export:"true"`
-	TLS                   *types.ClientTLS `description:"Enable TLS support." json:"tls,omitempty" toml:"tls,omitempty" yaml:"tls,omitempty" export:"true"`
+	Endpoint     string            `description:"Load configuration from this endpoint." json:"endpoint" toml:"endpoint" yaml:"endpoint"`
+	PollInterval ptypes.Duration   `description:"Polling interval for endpoint." json:"pollInterval,omitempty" toml:"pollInterval,omitempty" yaml:"pollInterval,omitempty" export:"true"`
+	PollTimeout  ptypes.Duration   `description:"Polling timeout for endpoint." json:"pollTimeout,omitempty" toml:"pollTimeout,omitempty" yaml:"pollTimeout,omitempty" export:"true"`
+	Headers      map[string]string `description:"Define custom headers to be sent to the endpoint." json:"headers,omitempty" toml:"headers,omitempty" yaml:"headers,omitempty" export:"true"`
+	TLS          *types.ClientTLS  `description:"Enable TLS support." json:"tls,omitempty" toml:"tls,omitempty" yaml:"tls,omitempty" export:"true"`
+
 	httpClient            *http.Client
 	lastConfigurationHash uint64
 }
@@ -139,9 +141,18 @@ func (p *Provider) updateConfiguration(configurationChan chan<- dynamic.Message)
 
 // fetchConfigurationData fetches the configuration data from the configured endpoint.
 func (p *Provider) fetchConfigurationData() ([]byte, error) {
-	res, err := p.httpClient.Get(p.Endpoint)
+	req, err := http.NewRequest(http.MethodGet, p.Endpoint, http.NoBody)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("create fetch request: %w", err)
+	}
+
+	for k, v := range p.Headers {
+		req.Header.Set(k, v)
+	}
+
+	res, err := p.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("do fetch request: %w", err)
 	}
 
 	defer res.Body.Close()

pkg/provider/http/http_test.go

@@ -69,35 +69,53 @@ func TestProvider_SetDefaults(t *testing.T) {
 
 func TestProvider_fetchConfigurationData(t *testing.T) {
 	tests := []struct {
-		desc    string
-		handler func(rw http.ResponseWriter, req *http.Request)
-		expData []byte
-		expErr  bool
+		desc       string
+		statusCode int
+		headers    map[string]string
+		expData    []byte
+		expErr     require.ErrorAssertionFunc
 	}{
 		{
-			desc:    "should return the fetched configuration data",
-			expData: []byte("{}"),
-			handler: func(rw http.ResponseWriter, req *http.Request) {
-				rw.WriteHeader(http.StatusOK)
-				_, _ = fmt.Fprintf(rw, "{}")
-			},
+			desc:       "should return the fetched configuration data",
+			statusCode: http.StatusOK,
+			expData:    []byte("{}"),
+			expErr:     require.NoError,
 		},
 		{
-			desc:   "should return an error if endpoint does not return an OK status code",
-			expErr: true,
-			handler: func(rw http.ResponseWriter, req *http.Request) {
-				rw.WriteHeader(http.StatusNoContent)
+			desc:       "should send configured headers",
+			statusCode: http.StatusOK,
+			headers: map[string]string{
+				"Foo": "bar",
+				"Bar": "baz",
 			},
+			expData: []byte("{}"),
+			expErr:  require.NoError,
+		},
+		{
+			desc:       "should return an error if endpoint does not return an OK status code",
+			statusCode: http.StatusInternalServerError,
+			expErr:     require.Error,
 		},
 	}
 
 	for _, test := range tests {
 		t.Run(test.desc, func(t *testing.T) {
-			server := httptest.NewServer(http.HandlerFunc(test.handler))
-			defer server.Close()
+			handlerCalled := false
+			srv := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+				handlerCalled = true
+
+				for k, v := range test.headers {
+					assert.Equal(t, v, req.Header.Get(k))
+				}
+
+				rw.WriteHeader(test.statusCode)
+				_, _ = rw.Write([]byte("{}"))
+			}))
+			defer srv.Close()
 
 			provider := Provider{
-				Endpoint:     server.URL,
+				Endpoint:     srv.URL,
+				Headers:      test.headers,
 				PollInterval: ptypes.Duration(1 * time.Second),
 				PollTimeout:  ptypes.Duration(1 * time.Second),
 			}
@@ -106,12 +124,9 @@ func TestProvider_fetchConfigurationData(t *testing.T) {
 			require.NoError(t, err)
 
 			configData, err := provider.fetchConfigurationData()
-			if test.expErr {
-				require.Error(t, err)
-				return
-			}
+			test.expErr(t, err)
 
-			require.NoError(t, err)
+			assert.True(t, handlerCalled)
 			assert.Equal(t, test.expData, configData)
 		})
 	}