share config for textfiles-directory

nixos/modules/monitoring/exporters/node.nix

@@ -15,6 +15,11 @@ let
 
 in {
   config.services.prometheus.exporters.node = {
+    textfiles-directory = lib.mkOption {
+      type = lib.types.str;
+      description = "Directory used by the textfiles collector.";
+      default = "/run/prometheus-node-exporter/tahoe.prom";
+    };
     enable = true;
     openFirewall = true;
     firewallFilter = "-i monitoringvpn -p tcp -m tcp --dport 9100";
@@ -36,7 +41,7 @@ in {
       "stat"
       "systemd"
       "textfile"
-      "textfile.directory /run/prometheus-node-exporter"
+      "textfile.directory ${cfg.textfiles-directory}"
       #"thermal_zone" # not in nixpkgs 19.09
       "time"
       #"udp_queues" # not in nixpkgs 19.09

nixos/modules/monitoring/exporters/tahoe.nix

@@ -11,6 +11,7 @@
 
 let
   cfg = config.services.private-storage.monitoring.tahoe;
+  inherit (config.services.private-storage.monitoring.node) textfiles-directory;
 
 in {
   options.services.private-storage.monitoring.tahoe = {
@@ -23,7 +24,7 @@ in {
     outFile = lib.mkOption {
       type = lib.types.str;
       description = "Where to store the temporary file for node exporter to scrape?";
-      default = "/run/prometheus-node-exporter/tahoe.prom";
+      default = "${textfiles-directory}/tahoe.prom";
     };
     interval = lib.mkOption {
       type = lib.types.str;