nixos/prometheus: require one alertmanager configuration parameter

This commit adds an assertion that checks that either `configFile` or
`configuration` is configured for alertmanager. The alertmanager config
can not be an empty attributeset. The check executed with `amtool` fails
before the service even has the chance to start. We should probably not
allow a broken alertmanager configuration anyway.

This also introduces a test for alertmanager configuration that piggy
backs on the existing prometheus tests.

1 files changed, 22 insertions, 0 deletions

diff --git a/nixos/tests/prometheus.nix b/nixos/tests/prometheus.nix
index 87a6510f40f..f1b20a33d71 100644
--- a/nixos/tests/prometheus.nix
+++ b/nixos/tests/prometheus.nix
@@ -13,6 +13,25 @@ import ./make-test.nix {
           }];
         }];
         rules = [ ''testrule = count(up{job="prometheus"})'' ];
+
+        # a very simple version of the alertmanager configuration just to see if
+        # configuration checks & service startup are working
+        alertmanager = {
+          enable = true;
+          listenAddress = "[::1]";
+          port = 9093;
+          configuration = {
+            route.receiver = "webhook";
+            receivers = [
+              {
+                name = "webhook";
+                webhook_configs = [
+                  { url = "http://localhost"; }
+                ];
+              }
+            ];
+          };
+        };
       };
     };
   };
@@ -22,5 +41,8 @@ import ./make-test.nix {
     $one->waitForUnit("prometheus.service");
     $one->waitForOpenPort(9090);
     $one->succeed("curl -s http://127.0.0.1:9090/metrics");
+    $one->waitForUnit("alertmanager.service");
+    $one->waitForOpenPort("9093");
+    $one->succeed("curl -f -s http://localhost:9093/");
   '';
 }