[nyarlathotep] Switch from promscale to VictoriaMetrics

Promscale was discontinued early last year, and around the beginning of
this year developed the irritating problem of frequently dropping data,
which led to me looking at the dashboard less and less often.

I tried using the prometheus backfilling tool, but couldn't get it to
work - it apparently loaded everything without error, but the metrics
just weren't there.  It also took 10m+ to load my historic hledger data,
which is far worse than the few seconds promscale took.

Today I found VictoriaMetrics, which falls into the same sweet spot as
promscale: it has an API that supports deleting timeseries and loading
data with arbitrary timestamps, and supports the prometheus query
language.  It works really well so far, and I've got my dashboard
working again!

hosts/nyarlathotep/configuration.nix

@@ -22,7 +22,6 @@ with lib;
 let
   shares = [ "anime" "manga" "misc" "music" "movies" "tv" "torrents" ];
 
-  promscalePort = 9201;
   prometheusAwairExporterPort = 9517;
 
   httpdir = "${toString config.nixfiles.eraseYourDarlings.persistDir}/srv/http";
@@ -359,8 +358,8 @@ in
     provision = {
       datasources.settings.datasources = [
         {
-          name = "promscale";
-          url = "http://localhost:${toString promscalePort}";
+          name = "victoriametrics";
+          url = "http://${config.services.victoriametrics.listenAddress}";
           type = "prometheus";
         }
       ];
@@ -462,46 +461,27 @@ in
     };
   };
 
-  systemd.services.hledger-export-to-promscale = {
-    description = "Export personal finance data to promscale";
+  systemd.services.hledger-export-to-victoriametrics = {
+    description = "Export personal finance data to VictoriaMetrics";
     startAt = "daily";
     path = with pkgs; [ hledger ];
     serviceConfig = {
       ExecStart =
         let python = pkgs.python3.withPackages (ps: [ ps.requests ]);
-        in "${python}/bin/python3 ${pkgs.writeText "hledger-export-to-promscale.py" (fileContents ./jobs/hledger-export-to-promscale.py)}";
+        in "${python}/bin/python3 ${pkgs.writeText "hledger-export-to-victoriametrics.py" (fileContents ./jobs/hledger-export-to-victoriametrics.py)}";
       User = "barrucadu";
       Group = "users";
     };
     environment = {
       LEDGER_FILE = "/home/barrucadu/s/ledger/combined.journal";
-      PROMSCALE_URI = "http://localhost:${toString promscalePort}";
+      VICTORIAMETRICS_URI = "http://${config.services.victoriametrics.listenAddress}";
     };
   };
 
-  nixfiles.oci-containers.pods.promscale = {
-    containers = {
-      web = {
-        image = "timescale/promscale:latest";
-        cmd = [
-          "-db.host=promscale-db"
-          "-db.name=postgres"
-          "-db.password=promscale"
-          "-db.ssl-mode=allow"
-          "-web.enable-admin-api=true"
-          "-metrics.promql.lookback-delta=168h"
-        ];
-        dependsOn = [ "promscale-db" ];
-        ports = [{ host = promscalePort; inner = 9201; }];
-      };
-      db = {
-        image = "timescaledev/promscale-extension:latest-ts2-pg14";
-        environment = {
-          POSTGRES_PASSWORD = "promscale";
-        };
-        volumes = [{ name = "pgdata"; inner = "/var/lib/postgresql/data"; }];
-      };
-    };
+  services.victoriametrics = {
+    enable = true;
+    listenAddress = "127.0.0.1:8428";
+    retentionPeriod = 1200;
   };