nixos/mackerel-agent: init

nixos/modules/module-list.nix

@@ -542,6 +542,7 @@
   ./services/monitoring/kapacitor.nix
   ./services/monitoring/loki.nix
   ./services/monitoring/longview.nix
+  ./services/monitoring/mackerel-agent.nix
   ./services/monitoring/monit.nix
   ./services/monitoring/munin.nix
   ./services/monitoring/nagios.nix

nixos/modules/services/monitoring/mackerel-agent.nix

@@ -0,0 +1,111 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.mackerel-agent;
+  settingsFmt = pkgs.formats.toml {};
+in {
+  options.services.mackerel-agent = {
+    enable = mkEnableOption "mackerel.io agent";
+
+    # the upstream package runs as root, but doesn't seem to be strictly
+    # necessary for basic functionality
+    runAsRoot = mkEnableOption "Whether to run as root.";
+
+    autoRetirement = mkEnableOption ''
+      Whether to automatically retire the host upon OS shutdown.
+    '';
+
+    apiKeyFile = mkOption {
+      type = types.path;
+      default = "";
+      example = "/run/keys/mackerel-api-key";
+      description = ''
+        Path to file containing the Mackerel API key. The file should contain a
+        single line of the following form:
+
+        <literallayout>apikey = "EXAMPLE_API_KEY"</literallayout>
+      '';
+    };
+
+    settings = mkOption {
+      description = ''
+        Options for mackerel-agent.conf.
+
+        Documentation:
+        <link xlink:href="https://mackerel.io/docs/entry/spec/agent"/>
+      '';
+
+      default = {};
+      example = {
+        verbose = false;
+        silent = false;
+      };
+
+      type = types.submodule {
+        freeformType = settingsFmt.type;
+
+        options.host_status = {
+          on_start = mkOption {
+            type = types.enum [ "working" "standby" "maintenance" "poweroff" ];
+            description = "Host status after agent startup.";
+            default = "working";
+          };
+          on_stop = mkOption {
+            type = types.enum [ "working" "standby" "maintenance" "poweroff" ];
+            description = "Host status after agent shutdown.";
+            default = "poweroff";
+          };
+        };
+
+        options.diagnostic =
+          mkEnableOption "Collect memory usage for the agent itself";
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = with pkgs; [ mackerel-agent ];
+
+    environment.etc = {
+      "mackerel-agent/mackerel-agent.conf".source =
+        settingsFmt.generate "mackerel-agent.conf" cfg.settings;
+      "mackerel-agent/conf.d/api-key.conf".source = cfg.apiKeyFile;
+    };
+
+    services.mackerel-agent.settings = {
+      root = mkDefault "/var/lib/mackerel-agent";
+      pidfile = mkDefault "/run/mackerel-agent/mackerel-agent.pid";
+
+      # conf.d stores the symlink to cfg.apiKeyFile
+      include = mkDefault "/etc/mackerel-agent/conf.d/*.conf";
+    };
+
+    # upstream service file in https://git.io/JUt4Q
+    systemd.services.mackerel-agent = {
+      description = "mackerel.io agent";
+      after = [ "network-online.target" "nss-lookup.target" ];
+      wantedBy = [ "multi-user.target" ];
+      environment = {
+        MACKEREL_PLUGIN_WORKDIR = mkDefault "%C/mackerel-agent";
+      };
+      serviceConfig = {
+        DynamicUser = !cfg.runAsRoot;
+        PrivateTmp = mkDefault true;
+        CacheDirectory = "mackerel-agent";
+        ConfigurationDirectory = "mackerel-agent";
+        RuntimeDirectory = "mackerel-agent";
+        StateDirectory = "mackerel-agent";
+        ExecStart = "${pkgs.mackerel-agent}/bin/mackerel-agent supervise";
+        ExecStopPost = mkIf cfg.autoRetirement "${pkg.mackerel-agent}/bin/mackerel-agent retire -force";
+        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
+        LimitNOFILE = mkDefault 65536;
+        LimitNPROC = mkDefault 65536;
+      };
+      restartTriggers = [
+        config.environment.etc."mackerel-agent/mackerel-agent.conf".source
+      ];
+    };
+  };
+}