nixos/prometheus: replace 'alertmanagerURL' options for prometheus2

Prometheus2 does no longer support the command-line flag to specify
an alertmanager. Instead it now supports both service discovery and
configuration of alertmanagers in the alerting config section.

Simply mapping the previous option to an entry in the new alertmanagers
section is not enough to allow for complete configurations of an
alertmanager.

Therefore the option alertmanagerURL is no longer used and instead
a full alertmanager configuration is expected.

1 files changed, 17 insertions, 9 deletions

diff --git a/nixos/modules/services/monitoring/prometheus/default.nix b/nixos/modules/services/monitoring/prometheus/default.nix
index d8384e0d35b3..647d67533b89 100644
--- a/nixos/modules/services/monitoring/prometheus/default.nix
+++ b/nixos/modules/services/monitoring/prometheus/default.nix
@@ -79,12 +79,8 @@ let
       (pkgs.writeText "prometheus.rules" (concatStringsSep "\n" cfg2.rules))
     ]);
     scrape_configs = filterValidPrometheus cfg2.scrapeConfigs;
-    alerting = optionalAttrs (cfg2.alertmanagerURL != []) {
-      alertmanagers = [{
-        static_configs = [{
-          targets = cfg2.alertmanagerURL;
-        }];
-      }];
+    alerting = {
+      inherit (cfg2) alertmanagers;
     };
   };
 
@@ -738,11 +734,23 @@ in {
         '';
       };
 
-      alertmanagerURL = mkOption {
-        type = types.listOf types.str;
+      alertmanagers = mkOption {
+        type = types.listOf types.attrs;
+        example = literalExample ''
+          [ {
+            scheme = "https";
+            path_prefix = "/alertmanager";
+            static_configs = [ {
+              targets = [
+                "prometheus.domain.tld"
+              ];
+            } ];
+          } ]
+        '';
         default = [];
         description = ''
-          List of Alertmanager URLs to send notifications to.
+          A list of alertmanagers to send alerts to.
+          See <link xlink:href="https://prometheus.io/docs/prometheus/latest/configuration/configuration/#alertmanager_config">the official documentation</link> for more information.
         '';
       };