Enable metrics for zrepl

build/pluto/prometheus/default.nix

@@ -21,6 +21,7 @@
     ./exporters/sql.nix
     ./exporters/up.nix
     ./exporters/zfs.nix
+    ./exporters/zrepl.nix
   ];
 
   services.backup.includesZfsDatasets = [ "/var/lib/prometheus2" ];

build/pluto/prometheus/exporters/zrepl.nix

@@ -0,0 +1,21 @@
+{ ... }:
+
+{
+  services.prometheus = {
+    scrapeConfigs = [
+      {
+        job_name = "zrepl";
+        static_configs = [
+          {
+            labels.role = "database";
+            targets = [
+              "titan.nixos.org:9811"
+            ];
+          }
+        ];
+      }
+    ];
+
+    # TODO: alert on `zrepl_replication_last_successful` being too long ago.
+  };
+}

build/titan/zrepl.nix

@@ -4,6 +4,9 @@
   ...
 }:
 
+let
+  metricsPort = 9811;
+in
 {
   age.secrets."zrepl-ssh-key" = {
     file = ../secrets/zrepl-ssh-key.age;
@@ -106,6 +109,14 @@
           ];
         };
 
+        # https://zrepl.github.io/configuration/monitoring.html
+        monitoring = [
+          {
+            type = "prometheus";
+            listen = ":${toString metricsPort}";
+          }
+        ];
+
         jobs = [
           # Covers 20240629+
           (
@@ -132,4 +143,9 @@
         ];
       };
     };
+
+  networking.firewall.extraInputRules = ''
+    ip6 saddr $prometheus_inet6 tcp dport ${toString metricsPort} accept
+    ip saddr $prometheus_inet4 tcp dport ${toString metricsPort} accept
+  '';
 }