maint: NixOS module writes config to the Nix store

Instead of writing the config attrset to a YAML file to a fixed path in /etc,
this makes the NixOS module write to a (content-addressed) config file in the
Nix store. We just use builtins.toJSON since YAML is a superset of JSON.

examples/example_dashboards.yaml

@@ -8,10 +8,8 @@
         - source: http://heimdall:9001 # Prometheus source uri for this plot
           query: 'sum by (instance)(irate(node_cpu_seconds_total{job="nodestats"}[5m]))' # The PromQL query for this plot
           meta: # metadata for this plot
-            name_label: instance # Grab a trace name from the query tags 
+            name_format: "`${labels.instance}`" # javascript template literal to format the trace name
             #d3_tick_format: "~%" # d3 tick format override for this plot's yaxis
-            #name_prefix: "Prefix" # A prefix for this sublots trace names
-            #name_suffix: "Suffix" # A suffix for this subplots trace names
             #named_axis: "y" # yaxis name to use for this subplots traces
       span: # The span for this range query
         end: now # Where the span ends. RFC3339 format with special handling for the now keyword
@@ -32,16 +30,14 @@
             sum by (instance)(irate(node_cpu_seconds_total{mode="system",job="nodestats"}[5m])) / sum by (instance)(irate(node_cpu_seconds_total{job="nodestats"}[5m]))
           meta:
             d3_tick_format: "~%"
-            name_label: instance
-            name_prefix: "System"
+            name_format: "`${labels.instance} system`"
             named_axis: "y"
         - source: http://heimdall:9001
           query: |
             sum by (instance)(irate(node_cpu_seconds_total{mode="user",job="nodestats"}[5m])) / sum by (instance)(irate(node_cpu_seconds_total{job="nodestats"}[5m]))
           meta:
             d3_tick_format: "~%"
-            name_label: instance
-            name_suffix: "User"
+            name_format: "`${labels.instance} user`"
             named_axis: "y"
     - title: Node memory
       query_type: Scalar
@@ -49,4 +45,4 @@
         - source: http://heimdall:9001
           query: 'node_memory_MemFree_bytes{job="nodestats"}'
           meta:
-            name_label: instance
+            name_format: "`${labels.instance}`"

flake.nix

@@ -83,9 +83,7 @@
                             sum by (instance)(irate(node_cpu_seconds_total{job="nodestats"}[5m]))
                           \'\';
                           meta = {
-                            name_label = "instance";
-                            name_prefix = "trace name prefix";
-                            name_suffix = "trace name suffix";
+                            name_function = "''${labels.instance}";
                             named_axis = "y";
                             # yaxis formatting for this subplot
                             d3_tick_format = "~s";
@@ -114,11 +112,9 @@
 
         config = let
           cfg = config.services.heracles;
+          cfgFile = pkgs.writeText "heracles.yaml" (builtins.toJSON cfg.settings);
         in
           lib.mkIf cfg.enable {
-            environment.etc."heracles.yaml" = {
-              text = lib.generators.toYAML {} cfg.settings;
-            };
             systemd.services.heracles = {
               wantedBy = ["multi-user.target" "default.target"];
               wants = ["network.target"];
@@ -126,7 +122,7 @@
               serviceConfig = {
                 Restart = "on-failure";
                 RestartSec = "30s";
-                ExecStart = "${pkgs.heracles}/bin/heracles --listen ${cfg.listen} --config=${config.environment.etc."heracles.yaml".target}";
+                ExecStart = "${pkgs.heracles}/bin/heracles --listen ${cfg.listen} --config=${cfgFile}";
               };
             };
           };

src/query.rs

@@ -117,9 +117,7 @@ pub struct DataPoint {
 
 #[derive(Serialize, Deserialize, Debug, Clone)]
 pub struct PlotMeta {
-    name_prefix: Option<String>,
-    name_suffix: Option<String>,
-    name_label: Option<String>,
+    name_format: Option<String>,
     named_axis: Option<String>,
     d3_tick_format: Option<String>,
 }

static/lib.js

@@ -160,19 +160,17 @@ class TimeseriesGraph extends HTMLElement {
                         yaxis: yaxis,
                         yhoverformat: meta["d3_tick_format"],
                     };
-                    const namePrefix = meta["name_prefix"];
-                    const nameSuffix = meta["name_suffix"];
-                    const nameLabel = meta["name_label"];
                     var name = "";
-                    if (namePrefix) {
-                        name = namePrefix + "-";
-                    };
-                    if (nameLabel && labels[nameLabel]) {
-                        name = name + labels[nameLabel];
-                    };
-                    if (nameSuffix) {
-                        name = name + " - " + nameSuffix;
-                    };
+                    const formatter = meta.name_format
+                    if (formatter) {
+                        name = eval(formatter);
+                    } else {
+                        var names = [];
+                        for (const value of labels) {
+                            names.push(value);
+                        }
+                        name = names.join(" ");
+                    }
                     if (name) { trace.name = name; }
                     for (const point of series) {
                         trace.x.push(new Date(point.timestamp * 1000));
@@ -190,17 +188,22 @@ class TimeseriesGraph extends HTMLElement {
                         type: "bar",
                         x: [],
                         y: [],
-                        yaxis: yaxis,
                         yhoverformat: meta["d3_tick_format"],
                     };
-                    let nameLabel = meta["name_label"];
-                    if (nameLabel && labels[nameLabel]) {
-                        trace.name = labels[nameLabel];
-                    };
-                    if (nameLabel && labels[nameLabel]) {
-                        trace.x.push(labels[nameLabel]);
-                    };
+                    const formatter = meta.name_format;
+                    var name = "";
+                    if (formatter) {
+                        name = eval(formatter);
+                    } else {
+                        var names = [];
+                        for (const value of labels) {
+                            names.push(value);
+                        }
+                        name = names.join(" ");
+                    }
+                    if (name) { trace.name = name; }
                     trace.y.push(series.value);
+                    trace.x.push(trace.name);
                     traces.push(trace);
                 }
             }