nixos/prometheus-rtl_433-exporter: new module

nixos/modules/services/monitoring/prometheus/exporters.nix

@@ -42,6 +42,7 @@ let
     "postgres"
     "redis"
     "rspamd"
+    "rtl_433"
     "snmp"
     "surfboard"
     "tor"
@@ -226,6 +227,8 @@ in
     services.prometheus.exporters.minio.minioAccessSecret = mkDefault config.services.minio.secretKey;
   })] ++ [(mkIf config.services.rspamd.enable {
     services.prometheus.exporters.rspamd.url = mkDefault "http://localhost:11334/stat";
+  })] ++ [(mkIf config.services.prometheus.exporters.rtl_433.enable {
+    hardware.rtl-sdr.enable = mkDefault true;
   })] ++ [(mkIf config.services.nginx.enable {
     systemd.services.prometheus-nginx-exporter.after = [ "nginx.service" ];
     systemd.services.prometheus-nginx-exporter.requires = [ "nginx.service" ];

nixos/modules/services/monitoring/prometheus/exporters/rtl_433.nix

@@ -0,0 +1,78 @@
+{ config, lib, pkgs, options }:
+
+let
+  cfg = config.services.prometheus.exporters.rtl_433;
+in
+{
+  port = 9550;
+
+  extraOpts = let
+    mkMatcherOptionType = field: description: with lib.types;
+      listOf (submodule {
+        options = {
+          name = lib.mkOption {
+            type = str;
+            description = "Name to match.";
+          };
+          "${field}" = lib.mkOption {
+            type = int;
+            inherit description;
+          };
+          location = lib.mkOption {
+            type = str;
+            description = "Location to match.";
+          };
+        };
+      });
+  in
+  {
+    rtl433Flags = lib.mkOption {
+      type = lib.types.str;
+      default = "-C si";
+      example = "-C si -R 19";
+      description = ''
+        Flags passed verbatim to rtl_433 binary.
+        Having <literal>-C si</literal> (the default) is recommended since only Celsius temperatures are parsed.
+      '';
+    };
+    channels = lib.mkOption {
+      type = mkMatcherOptionType "channel" "Channel to match.";
+      default = [];
+      example = [
+        { name = "Acurite"; channel = 6543; location = "Kitchen"; }
+      ];
+      description = ''
+        List of channel matchers to export.
+      '';
+    };
+    ids = lib.mkOption {
+      type = mkMatcherOptionType "id" "ID to match.";
+      default = [];
+      example = [
+        { name = "Nexus"; id = 1; location = "Bedroom"; }
+      ];
+      description = ''
+        List of ID matchers to export.
+      '';
+    };
+  };
+
+  serviceOpts = {
+    serviceConfig = {
+      # rtl-sdr udev rules make supported USB devices +rw by plugdev.
+      SupplementaryGroups = "plugdev";
+      ExecStart = let
+        matchers = (map (m:
+          "--channel_matcher '${m.name},${toString m.channel},${m.location}'"
+        ) cfg.channels) ++ (map (m:
+          "--id_matcher '${m.name},${toString m.id},${m.location}'"
+        ) cfg.ids); in ''
+        ${pkgs.prometheus-rtl_433-exporter}/bin/rtl_433_prometheus \
+          -listen ${cfg.listenAddress}:${toString cfg.port} \
+          -subprocess "${pkgs.rtl_433}/bin/rtl_433 -F json ${cfg.rtl433Flags}" \
+          ${lib.concatStringsSep " \\\n  " matchers} \
+          ${lib.concatStringsSep " \\\n  " cfg.extraFlags}
+      '';
+    };
+  };
+}

nixos/tests/prometheus-exporters.nix

@@ -536,6 +536,37 @@ let
       '';
     };
 
+    rtl_433 = {
+      exporterConfig = {
+        enable = true;
+      };
+      metricProvider = {
+        # Mock rtl_433 binary to return a dummy metric stream.
+        nixpkgs.overlays = [ (self: super: {
+          rtl_433 = self.runCommand "rtl_433" {} ''
+            mkdir -p "$out/bin"
+            cat <<EOF > "$out/bin/rtl_433"
+            #!/bin/sh
+            while true; do
+              printf '{"time" : "2020-04-26 13:37:42", "model" : "zopieux", "id" : 55, "channel" : 3, "temperature_C" : 18.000}\n'
+              sleep 4
+            done
+            EOF
+            chmod +x "$out/bin/rtl_433"
+          '';
+        }) ];
+      };
+      exporterTest = ''
+        wait_for_unit("prometheus-rtl_433-exporter.service")
+        wait_for_open_port(9550)
+        wait_until_succeeds(
+            "curl -sSf localhost:9550/metrics | grep -q '{}'".format(
+                'rtl_433_temperature_celsius{channel="3",id="55",location="",model="zopieux"} 18'
+            )
+        )
+      '';
+    };
+
     snmp = {
       exporterConfig = {
         enable = true;