From e3a0c808cff4de07c2f5749798daf56b932a6c37 Mon Sep 17 00:00:00 2001
From: Ruben Maher <ruben@maher.fyi>
Date: Fri, 17 Aug 2018 14:16:23 +0930
Subject: [PATCH] modules/alertmanager: add clusterAdvertiseAddress option

Alertmanager fails to start when the memberlist library cannot find any private
IP addresses on the system.  This is a safeguard to avoid exposing cluster ports
over the internet unintentionally.  The workaround is to pass the
--cluster.advertise-address argument to AlertManager.

See also:
https://github.com/prometheus/alertmanager/pull/1437
https://github.com/prometheus/alertmanager/issues/1434
---
 .../services/monitoring/prometheus/alertmanager.nix  | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/nixos/modules/services/monitoring/prometheus/alertmanager.nix b/nixos/modules/services/monitoring/prometheus/alertmanager.nix
index 8a47c9f1e7d89c..24c564d9adaef6 100644
--- a/nixos/modules/services/monitoring/prometheus/alertmanager.nix
+++ b/nixos/modules/services/monitoring/prometheus/alertmanager.nix
@@ -30,6 +30,17 @@ in {
         '';
       };
 
+      clusterAdvertiseAddress = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          If Alertmanager cannot find any private IP address on the host
+          machine, will fail to start unless an explicit advertise address is
+          provided.  In that case, you can use the machine's public IP address
+          here.
+        '';
+      };
+
       configuration = mkOption {
         type = types.attrs;
         default = {};
@@ -115,6 +126,7 @@ in {
         --web.listen-address ${cfg.listenAddress}:${toString cfg.port} \
         --log.level ${cfg.logLevel} \
         ${optionalString (cfg.webExternalUrl != null) ''--web.external-url ${cfg.webExternalUrl} \''}
+        ${optionalString (cfg.clusterAdvertiseAddress != null) ''--cluster.advertise-address ${cfg.clusterAdvertiseAddress} \''}
         ${optionalString (cfg.logFormat != null) "--log.format ${cfg.logFormat}"}
       '';