feat: unibus_exporter — daemon que sondea /healthz del cluster unibus y empuja estado+posture a VictoriaMetrics

Compone parse_unibus_health + format_prom_exposition + push_prom_remote del registry
(grupo fleet-metrics). Un solo exporter scrapea los 3 nodos por IP pública con la CA
del cluster; labels node/instance por serie. Config JSON con secretos fuera de argv.
Incluye systemd unit y unibus.example.json.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

config.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+)
+
+// Node is a single unibus cluster member to probe. Name is the logical node
+// label ("magnus", "homer", "datardos"); URL is its full /healthz endpoint
+// (e.g. https://135.125.201.30:8470/healthz).
+type Node struct {
+	Name string `json:"name"`
+	URL  string `json:"url"`
+}
+
+// Config is the exporter runtime configuration, read from a JSON file. It holds
+// the list of unibus nodes to probe, the cluster CA used to verify their TLS,
+// the VictoriaMetrics ingest endpoint and its basic-auth credentials.
+//
+// Secrets (pass) live only in this file (chmod 600) or come from the environment
+// — never in argv. The example config carries a placeholder, not the real one.
+type Config struct {
+	Nodes       []Node            `json:"nodes"`         // unibus members to probe
+	CACertPath  string            `json:"ca_cert_path"`  // PEM CA of the unibus cluster, used to verify each node's TLS
+	HubURL      string            `json:"hub_url"`       // VictoriaMetrics import endpoint (…/api/v1/import/prometheus)
+	User        string            `json:"user"`          // basic-auth user for the hub (empty disables auth)
+	Pass        string            `json:"pass"`          // basic-auth password for the hub
+	IntervalSec int               `json:"interval_sec"`  // scrape+push period in seconds (default 15)
+	TimeoutSec  int               `json:"timeout_sec"`   // per-node healthz GET timeout in seconds (default 8)
+	Labels      map[string]string `json:"labels"`        // extra labels added to every series via extra_label (e.g. {"job":"unibus_exporter"})
+}
+
+// loadConfig reads and validates the JSON config at path. Environment overrides:
+// UNIBUS_HUB_URL, UNIBUS_USER, UNIBUS_PASS, UNIBUS_CA_CERT, UNIBUS_INTERVAL.
+func loadConfig(path string) (Config, error) {
+	cfg := Config{IntervalSec: 15, TimeoutSec: 8}
+	if path != "" {
+		b, err := os.ReadFile(path)
+		if err != nil {
+			return cfg, err
+		}
+		if err := json.Unmarshal(b, &cfg); err != nil {
+			return cfg, err
+		}
+	}
+	if v := os.Getenv("UNIBUS_HUB_URL"); v != "" {
+		cfg.HubURL = v
+	}
+	if v := os.Getenv("UNIBUS_USER"); v != "" {
+		cfg.User = v
+	}
+	if v := os.Getenv("UNIBUS_PASS"); v != "" {
+		cfg.Pass = v
+	}
+	if v := os.Getenv("UNIBUS_CA_CERT"); v != "" {
+		cfg.CACertPath = v
+	}
+	if v := os.Getenv("UNIBUS_INTERVAL"); v != "" {
+		if n, err := parsePositiveInt(v); err == nil {
+			cfg.IntervalSec = n
+		}
+	}
+	if cfg.IntervalSec <= 0 {
+		cfg.IntervalSec = 15
+	}
+	if cfg.TimeoutSec <= 0 {
+		cfg.TimeoutSec = 8
+	}
+	if cfg.Labels == nil {
+		cfg.Labels = map[string]string{"job": "unibus_exporter"}
+	} else if _, ok := cfg.Labels["job"]; !ok {
+		cfg.Labels["job"] = "unibus_exporter"
+	}
+	return cfg, validate(cfg)
+}
+
+func validate(cfg Config) error {
+	if cfg.HubURL == "" {
+		return fmt.Errorf("hub_url is required")
+	}
+	if len(cfg.Nodes) == 0 {
+		return fmt.Errorf("at least one node is required")
+	}
+	if cfg.CACertPath == "" {
+		return fmt.Errorf("ca_cert_path is required (PEM CA of the unibus cluster)")
+	}
+	for i, n := range cfg.Nodes {
+		if n.Name == "" || n.URL == "" {
+			return fmt.Errorf("node[%d]: name and url are required", i)
+		}
+	}
+	return nil
+}
+
+func parsePositiveInt(s string) (int, error) {
+	var n int
+	_, err := fmt.Sscanf(s, "%d", &n)
+	if err != nil {
+		return 0, err
+	}
+	if n <= 0 {
+		return 0, fmt.Errorf("not positive")
+	}
+	return n, nil
+}