alertmanger: Add setting to overwrite URL

README.md

@@ -77,6 +77,9 @@ alertmanager {
     # Basic authentication (https://prometheus.io/docs/alerting/latest/https/)
     user user
     password pass
+    # By default the Alertmanager URL gets parsed from the webhook. In case that
+    # Alertmanger is not reachable under that URL, it can be overwritten here.
+    url https://alertmanager.xenrox.net
 }
 
 # When the alert-mode is set to single, ntfy-alertmanager will cache each single alert

config.go

@@ -53,6 +53,7 @@ type alertmanagerConfig struct {
 	User            string
 	Password        string
 	SilenceDuration time.Duration
+	URL             string
 }
 
 func readConfig(path string) (*config, error) {
@@ -262,6 +263,13 @@ func readConfig(path string) (*config, error) {
 				return nil, err
 			}
 		}
+
+		d = amDir.Children.Get("url")
+		if d != nil {
+			if err := d.ParseParams(&config.am.URL); err != nil {
+				return nil, err
+			}
+		}
 	}
 
 	return config, nil

config_test.go

@@ -58,6 +58,7 @@ alertmanager {
     # Basic authentication (https://prometheus.io/docs/alerting/latest/https/)
     user user
     password pass
+    url https://alertmanager.xenrox.net
 }
 
 # When the alert-mode is set to single, ntfy-alertmanager will cache each single alert
@@ -90,6 +91,7 @@ cache {
 			SilenceDuration: time.Hour * 24,
 			User:            "user",
 			Password:        "pass",
+			URL:             "https://alertmanager.xenrox.net",
 		},
 	}
 

silence.go

@@ -87,7 +87,13 @@ func (rcv *receiver) handleSilences(w http.ResponseWriter, r *http.Request) {
 	}
 
 	client := &http.Client{Timeout: time.Second * 3}
-	url := sb.AlertManagerURL + "/api/v2/silences"
+
+	url := sb.AlertManagerURL
+	if rcv.cfg.am.URL != "" {
+		url = rcv.cfg.am.URL
+	}
+	url += "/api/v2/silences"
+
 	req, err := http.NewRequest(http.MethodPost, url, bytes.NewBuffer(b))
 	if err != nil {
 		rcv.logger.Debugf("silences: %v", err)