alloy

name	alloy
license	Apache-2.0
description	Build a unified telemetry pipeline with Grafana Alloy — one OpenTelemetry-compatible binary that collects metrics, logs, traces, and profiles and ships to Grafana Cloud / Prometheus / Loki / Tempo / Pyroscope. Covers the Alloy config language (blocks, `sys.env`, component refs), `prometheus.scrape` → `remote_write`, `loki.source.file` + `loki.process` → `loki.write`, `otelcol.receiver.otlp` → `otelcol.exporter.otlp`, `pyroscope.scrape`, K8s / Docker / EC2 discovery, relabeling, modules (`import.file/git/http`), clustering, Fleet Management `remotecfg`, the Alloy UI at `:12345`, and `alloy fmt` / `alloy validate`. Use when writing a `config.alloy`, replacing Grafana Agent / OTel Collector, scraping K8s pods, parsing logs, ingesting OTLP, or debugging "Alloy isn't sending anything" — even when the user says "set up the agent", "write me a scrape config", "drop these logs before sending", or "OTel collector config" without naming Alloy.

Grafana Alloy

Docs: https://grafana.com/docs/alloy/latest/

OpenTelemetry-compatible collector — one binary for metrics + logs + traces + profiles.

Prerequisites

• alloy CLI installed (brew install grafana/grafana/alloy, apt install alloy, or grafana/alloy Docker image)
• An endpoint to ship to (Grafana Cloud, Prometheus, Loki, Tempo, Pyroscope)
• API key + username for that endpoint, exported as GRAFANA_API_KEY etc.

Common Workflows

1. Write + validate a config locally

// config.alloy — metrics → Grafana Cloud
prometheus.scrape "app" {
  targets = [{"__address__" = "localhost:9090"}]
  forward_to = [prometheus.remote_write.cloud.receiver]
  scrape_interval = "30s"
}

prometheus.remote_write "cloud" {
  endpoint {
    url = sys.env("PROMETHEUS_URL")
    basic_auth {
      username = sys.env("PROM_USER")
      password = sys.env("GRAFANA_API_KEY")
    }
  }
}

# 1. Format + syntax-check (catches typos before run)
alloy fmt config.alloy
alloy validate config.alloy

# 2. Run it
alloy run config.alloy
# or as a service: systemctl restart alloy

# 3. Verify all components are healthy via the UI on port 12345
curl -s http://localhost:12345/api/v0/web/components \
  | jq '.[] | select(.health.state != "healthy") | {id, state:.health.state, msg:.health.message}'
# Expect: empty (nothing unhealthy). Otherwise the row shows the failing component + reason.

# 4. Verify samples are flowing
curl -s http://localhost:12345/metrics \
  | grep -E '^prometheus_remote_storage_(samples_total|enqueue_retries_total)' | head
# samples_total should be > 0 and rising; retries should be 0.

2. Add log shipping (file → Loki)

loki.source.file "app_logs" {
  targets    = [{ __path__ = "/var/log/app/*.log", job = "app" }]
  forward_to = [loki.write.cloud.receiver]
}

loki.write "cloud" {
  endpoint {
    url = sys.env("LOKI_URL")
    basic_auth {
      username = sys.env("LOKI_USER")
      password = sys.env("GRAFANA_API_KEY")
    }
  }
}

# Verify in Grafana → Explore → Loki:
#   {job="app"}
# Expect lines streaming. If empty:
#   - check /var/log/app/*.log actually exists + readable by the alloy user
#   - http://localhost:12345 → loki.source.file.app_logs → "Targets" tab

3. Receive OTLP traces and ship to Tempo

otelcol.receiver.otlp "default" {
  grpc { endpoint = "0.0.0.0:4317" }
  http { endpoint = "0.0.0.0:4318" }
  output { traces = [otelcol.exporter.otlp.tempo.input] }
}

otelcol.exporter.otlp "tempo" {
  client {
    endpoint = "tempo-xxx.grafana.net/tempo:443"
    auth     = otelcol.auth.basic.grafana_cloud.handler
  }
}

otelcol.auth.basic "grafana_cloud" {
  username = sys.env("TEMPO_USER")
  password = sys.env("GRAFANA_API_KEY")
}

# Verify in Grafana → Explore → Tempo → service.name = your-service
# At the Alloy level, watch the receiver:
curl -s http://localhost:12345/metrics | grep otelcol_receiver_accepted_spans

Full pattern set (Kubernetes discovery + relabel, complete Cloud pipeline for all 4 signals): references/collection-patterns.md.

Reference

• references/config-syntax.md — block/attribute/expression grammar, import.*, remotecfg, clustering
• references/components.md — full component catalog with purpose + typical args
• references/collection-patterns.md — end-to-end pipelines (K8s pods, OTLP, profiles, logs)

Troubleshooting

• alloy validate → "component not found" → version too old; alloy --version and upgrade
• UI shows component unhealthy → click into it on http://localhost:12345 for the live error
• prometheus_remote_storage_samples_dropped_total rising → check enqueue_retries_total and the remote_write endpoint URL + creds
• No spans landing in Tempo → check otelcol_receiver_refused_spans and the exporter's otelcol_exporter_sent_spans / otelcol_exporter_send_failed_spans

Resources

• Alloy docs
• Component reference
• Migrate from Grafana Agent