// Managed by Ansible. River config for Grafana Alloy.
//
// Two scrape jobs:
//   - node_exporter (host: CPU, mem, disk, network, fs, etc.)
//   - shithubd /metrics (app: req latency, DB pool, panics, jobs)
//
// Both push to Grafana Cloud Mimir via the prometheus.remote_write
// component below. The basic-auth username/password come from
// /etc/alloy/credentials.env via EnvironmentFile= on the unit.
//
// Why this shape (not separate prometheus + grafana on the droplet):
// - One binary, one config, one systemd unit.
// - No inbound 9090 to firewall — push-only.
// - Free-tier Grafana Cloud handles ~10k active series, way over
//   what one shithubd droplet emits.

prometheus.remote_write "grafana_cloud" {
  endpoint {
    url = sys.env("GRAFANA_CLOUD_PROM_URL")
    basic_auth {
      username = sys.env("GRAFANA_CLOUD_PROM_USER")
      password = sys.env("GRAFANA_CLOUD_PROM_TOKEN")
    }
  }
  // Drop the most cardinality-expensive labels from go runtime metrics
  // before remote_write. The free tier limits unique series; bare go_*
  // gives plenty of signal without the per-bucket explosions.
  external_labels = {
    instance = "{{ ansible_hostname }}",
    cluster  = "shithub-prod",
  }
}

// ── node_exporter ───────────────────────────────────────────────
prometheus.scrape "node_exporter" {
  targets = [
    { __address__ = "127.0.0.1:9100", job = "node" },
  ]
  forward_to     = [prometheus.remote_write.grafana_cloud.receiver]
  scrape_interval = "30s"
  scrape_timeout  = "10s"
}

// ── shithubd /metrics ───────────────────────────────────────────
// enable_compression = false: shithubd's HTTP middleware auto-gzips
// when the client advertises Accept-Encoding: gzip and correctly sets
// Content-Encoding: gzip on the response. Alloy 1.16's Prometheus
// scraper mis-handles that path: it parses the raw 0x1f gzip magic
// byte as text and the scrape fails with up=0. Disabling Accept-
// Encoding negotiation forces shithubd to return plain text. The
// /metrics payload is small enough that wire-size cost is irrelevant.
// Revisit once Alloy fixes the gzip-aware text parser upstream.
prometheus.scrape "shithubd" {
  targets = [
    { __address__ = "127.0.0.1:8080", job = "shithubd", __metrics_path__ = "/metrics" },
  ]
  forward_to         = [prometheus.remote_write.grafana_cloud.receiver]
  scrape_interval    = "15s"
  scrape_timeout     = "10s"
  enable_compression = false
}