feat(backend): add support for custom headers (#368)

This will allow the AlertManager upstreams to be sent user defined HTTP headers.

.gitignore

@@ -1,6 +1,7 @@
 .build
 .coverage
 .tests
+.vscode
 bindata_assetfs.go
 coverage.txt
 karma

docs/CONFIGURATION.md

@@ -41,6 +41,8 @@ alertmanager:
         ca: string
         cert: string
         key: string
+      headers:
+        any: string
 ```
 
 - `interval` - how often alerts should be refreshed, a string in
@@ -85,9 +87,12 @@ alertmanager:
   TLS connections to this Alertmanager instance if it requires a TLS client
   authentication.
   Note that this option requires `tls:cert` to be also set.
+- `headers` - a map with a list of key: values which are header: value.
+  These custom headers will be sent with every request to the alert manager
+  instance.
 
 Example with two production Alertmanager instances running in HA mode and a
-staging instance that is also proxied:
+staging instance that is also proxied and requires a custom auth header:
 
 ```yaml
 alertmanager:
@@ -107,6 +112,8 @@ alertmanager:
       proxy: true
       tls:
         ca: /etc/ssl/staging-ca.crt
+      headers:
+        X-Auth-Token: aValidToken
     - name: protected
       uri: https://alertmanager-auth.prod.example.com
       timeout: 20s

docs/example.yaml

@@ -5,6 +5,8 @@ alertmanager:
       uri: http://localhost:9093
       timeout: 10s
       proxy: true
+      headers:
+        X-Auth-Test: some-token-or-other-string
     - name: client-auth
       uri: https://localhost:9093
       timeout: 10s

internal/alertmanager/models.go

@@ -61,6 +61,8 @@ type Alertmanager struct {
 	status       alertmanagerStatus
 	// metrics tracked per alertmanager instance
 	metrics alertmanagerMetrics
+	// headers to send with each AlertManager request
+	HTTPHeaders map[string]string
 }
 
 func (am *Alertmanager) fetchStatus() alertmanagerStatus {
@@ -80,7 +82,7 @@ func (am *Alertmanager) fetchStatus() alertmanagerStatus {
 	resp := alertmanagerStatusResponse{}
 
 	// read raw body from the source
-	source, err := am.reader.Read(url)
+	source, err := am.reader.Read(url, am.HTTPHeaders)
 	if err != nil {
 		log.Errorf("[%s] %s request failed: %s", am.Name, uri.SanitizeURI(url), err)
 		return status
@@ -157,7 +159,7 @@ func (am *Alertmanager) pullSilences(version string) error {
 
 	start := time.Now()
 	// read raw body from the source
-	source, err := am.reader.Read(url)
+	source, err := am.reader.Read(url, am.HTTPHeaders)
 	if err != nil {
 		log.Errorf("[%s] %s request failed: %s", am.Name, uri.SanitizeURI(url), err)
 		return err
@@ -222,7 +224,7 @@ func (am *Alertmanager) pullAlerts(version string) error {
 
 	start := time.Now()
 	// read raw body from the source
-	source, err := am.reader.Read(url)
+	source, err := am.reader.Read(url, am.HTTPHeaders)
 	if err != nil {
 		log.Errorf("[%s] %s request failed: %s", am.Name, uri.SanitizeURI(url), err)
 		return err

internal/alertmanager/upstream.go

@@ -31,6 +31,7 @@ func NewAlertmanager(name, upstreamURI string, opts ...Option) (*Alertmanager, e
 		colors:         models.LabelsColorMap{},
 		autocomplete:   []models.Autocomplete{},
 		knownLabels:    []string{},
+		HTTPHeaders:    map[string]string{},
 		metrics: alertmanagerMetrics{
 			errors: map[string]float64{
 				labelValueErrorsAlerts:   0,
@@ -48,7 +49,7 @@ func NewAlertmanager(name, upstreamURI string, opts ...Option) (*Alertmanager, e
 	}
 
 	var err error
-	am.reader, err = uri.NewReader(am.URI, am.RequestTimeout, am.HTTPTransport)
+	am.reader, err = uri.NewReader(am.URI, am.RequestTimeout, am.HTTPTransport, am.HTTPHeaders)
 	if err != nil {
 		return am, err
 	}
@@ -110,6 +111,15 @@ func WithRequestTimeout(timeout time.Duration) Option {
 	}
 }
 
+// WithHTTPHeaders option can be passed to NewAlertManager in order to set
+// a map of headers that will be passed with every request
+func WithHTTPHeaders(headers map[string]string) Option {
+	return func(am *Alertmanager) error {
+		am.HTTPHeaders = headers
+		return nil
+	}
+}
+
 // WithHTTPTransport option can be passed to NewAlertmanager in order to set
 // a custom HTTP transport (http.RoundTripper implementation)
 func WithHTTPTransport(httpTransport http.RoundTripper) Option {

internal/config/config.go

@@ -170,6 +170,7 @@ func (config *configSchema) Read() {
 				URI:     v.GetString("alertmanager.uri"),
 				Timeout: v.GetDuration("alertmanager.timeout"),
 				Proxy:   v.GetBool("alertmanager.proxy"),
+				Headers: make(map[string]string),
 			},
 		}
 	}

internal/config/config_test.go

@@ -64,6 +64,7 @@ func testReadConfig(t *testing.T) {
       ca: ""
       cert: ""
       key: ""
+    headers: {}
 annotations:
   default:
     hidden: true

internal/config/models.go

@@ -12,6 +12,7 @@ type alertmanagerConfig struct {
 		Cert string
 		Key  string
 	}
+	Headers map[string]string
 }
 
 type jiraRule struct {

internal/uri/file.go

@@ -46,7 +46,7 @@ func (r *FileURIReader) pathFromURI(uri string) (string, error) {
 	return absolutePath, nil
 }
 
-func (r *FileURIReader) Read(uri string) (io.ReadCloser, error) {
+func (r *FileURIReader) Read(uri string, _ map[string]string) (io.ReadCloser, error) {
 	filename, err := r.pathFromURI(uri)
 	if err != nil {
 		return nil, err

internal/uri/http.go

@@ -14,7 +14,7 @@ type HTTPURIReader struct {
 	client http.Client
 }
 
-func (r *HTTPURIReader) Read(uri string) (io.ReadCloser, error) {
+func (r *HTTPURIReader) Read(uri string, headers map[string]string) (io.ReadCloser, error) {
 	log.Infof("GET %s timeout=%s", SanitizeURI(uri), r.client.Timeout)
 
 	request, err := http.NewRequest("GET", uri, nil)
@@ -23,6 +23,10 @@ func (r *HTTPURIReader) Read(uri string) (io.ReadCloser, error) {
 	}
 	request.Header.Add("Accept-Encoding", "gzip")
 
+	for header, value := range headers {
+		request.Header.Add(header, value)
+	}
+
 	resp, err := r.client.Do(request)
 	if err != nil {
 		return nil, err

internal/uri/uri.go

@@ -10,12 +10,12 @@ import (
 
 // Reader reads from a specific URI schema
 type Reader interface {
-	Read(string) (io.ReadCloser, error)
+	Read(string, map[string]string) (io.ReadCloser, error)
 }
 
 // NewReader creates an instance of URIReader that can handle URI schema
 // for the passed uri string
-func NewReader(uri string, timeout time.Duration, clientTransport http.RoundTripper) (Reader, error) {
+func NewReader(uri string, timeout time.Duration, clientTransport http.RoundTripper, headers map[string]string) (Reader, error) {
 	u, err := url.Parse(uri)
 	if err != nil {
 		return nil, err

internal/uri/uri_test.go

@@ -34,11 +34,12 @@ type httpTransportTest struct {
 	useTLS    bool
 	tlsConfig *tls.Config
 	failed    bool
+	headers   map[string]string
 }
 
 var httpTransportTests = []httpTransportTest{
 	{
-	// plain HTTP request, should work
+		// plain HTTP request, should work
 	},
 	{
 		// just enable TLS, will use proper RootCA certs so it should work
@@ -50,6 +51,9 @@ var httpTransportTests = []httpTransportTest{
 		tlsConfig: &tls.Config{RootCAs: x509.NewCertPool()},
 		failed:    true,
 	},
+	{
+		headers: map[string]string{"X-Auth-Test": "tokenValue"},
+	},
 }
 
 type fileTransportTest struct {
@@ -57,6 +61,7 @@ type fileTransportTest struct {
 	failed  bool
 	timeout time.Duration
 	size    int64
+	headers map[string]string
 }
 
 var fileTransportTests = []fileTransportTest{
@@ -124,12 +129,12 @@ func TestHTTPReader(t *testing.T) {
 			tlsConfig = &tls.Config{RootCAs: caPool}
 		}
 
-		transp, err := uri.NewReader(amURI, testCase.timeout, &http.Transport{TLSClientConfig: tlsConfig})
+		transp, err := uri.NewReader(amURI, testCase.timeout, &http.Transport{TLSClientConfig: tlsConfig}, testCase.headers)
 		if err != nil {
 			t.Errorf("[%v] failed to create new HTTP transport: %s", testCase, err)
 		}
 
-		source, err := transp.Read(amURI)
+		source, err := transp.Read(amURI, testCase.headers)
 		if err != nil {
 			if !testCase.failed {
 				t.Errorf("[%v] unexpected failure while creating reader: %s", testCase, err)
@@ -152,12 +157,12 @@ func TestHTTPReader(t *testing.T) {
 func TestFileReader(t *testing.T) {
 	//log.SetLevel(log.FatalLevel)
 	for _, testCase := range fileTransportTests {
-		transp, err := uri.NewReader(testCase.uri, testCase.timeout, &http.Transport{})
+		transp, err := uri.NewReader(testCase.uri, testCase.timeout, &http.Transport{}, testCase.headers)
 		if err != nil {
 			t.Errorf("[%v] failed to create new transport: %s", testCase, err)
 		}
 
-		source, err := transp.Read(testCase.uri)
+		source, err := transp.Read(testCase.uri, testCase.headers)
 		if err != nil {
 			if !testCase.failed {
 				t.Errorf("[%v] unexpected failure while creating reader: %s", testCase, err)

main.go

@@ -116,6 +116,7 @@ func setupUpstreams() {
 			alertmanager.WithRequestTimeout(s.Timeout),
 			alertmanager.WithProxy(s.Proxy),
 			alertmanager.WithHTTPTransport(httpTransport), // we will pass a nil unless TLS.CA or TLS.Cert is set
+			alertmanager.WithHTTPHeaders(s.Headers),
 		)
 		if err != nil {
 			log.Fatalf("Failed to create Alertmanager '%s' with URI '%s': %s", s.Name, s.URI, err)