nixos/tests: add test for loki

nixos/tests/all-tests.nix

@@ -139,6 +139,7 @@ in
   #lightdm = handleTest ./lightdm.nix {};
   limesurvey = handleTest ./limesurvey.nix {};
   login = handleTest ./login.nix {};
+  loki = handleTest ./loki.nix {};
   #logstash = handleTest ./logstash.nix {};
   mailcatcher = handleTest ./mailcatcher.nix {};
   mathics = handleTest ./mathics.nix {};

nixos/tests/loki.nix

@@ -0,0 +1,37 @@
+import ./make-test.nix ({ lib, pkgs, ... }:
+
+{
+  name = "loki";
+
+  meta = with lib.maintainers; {
+    maintainers = [ willibutz ];
+  };
+
+  machine = { ... }: {
+    services.loki = {
+      enable = true;
+      configFile = "${pkgs.grafana-loki.src}/cmd/loki/loki-local-config.yaml";
+    };
+    systemd.services.promtail = {
+      description = "Promtail service for Loki test";
+      wantedBy = [ "multi-user.target" ];
+
+      serviceConfig = {
+        ExecStart = ''
+          ${pkgs.grafana-loki}/bin/promtail --config.file ${pkgs.grafana-loki.src}/cmd/promtail/promtail-local-config.yaml
+        '';
+        DynamicUser = true;
+      };
+    };
+  };
+
+  testScript = ''
+    $machine->start;
+    $machine->waitForUnit("loki.service");
+    $machine->waitForUnit("promtail.service");
+    $machine->waitForOpenPort(3100);
+    $machine->waitForOpenPort(9080);
+    $machine->succeed("echo 'Loki Ingestion Test' > /var/log/testlog");
+    $machine->waitUntilSucceeds("${pkgs.grafana-loki}/bin/logcli --addr='http://localhost:3100' query --no-labels '{job=\"varlogs\",filename=\"/var/log/testlog\"}' | grep -q 'Loki Ingestion Test'");
+  '';
+})