elixir-phoenix-observability

name	elixir-phoenix-observability
description	Set up or review Phoenix telemetry, metrics, traces, logs, and alerts.
metadata	{"short-description":"Review Phoenix telemetry and alerts"}

Observability

Use when the user needs measurable system health and faster debugging in production.

When to Use

• Adding or auditing Telemetry instrumentation
• Defining service-level indicators and alerts
• Wiring OpenTelemetry traces across Phoenix/Ecto/Oban
• Improving log correlation for incidents
• Building dashboards for latency, throughput, and errors

Iron Laws

1. Instrument user-impacting flows before adding low-value metrics.
2. Every alert must map to an explicit operator action.
3. Logs must be structured and scrubbed for secrets.
4. Trace/span names must be stable and domain-oriented.
5. Prefer a small reliable metric set over noisy dashboards.

Workflow

Step 1: Define Signals

For each critical flow, define:

• Latency (p50/p95/p99)
• Throughput (requests/jobs per minute)
• Error rate (and top failure classes)
• Saturation indicators (DB pool, queue depth, scheduler pressure)

Step 2: Instrument

Verify or add:

• Telemetry events at Phoenix and domain boundaries
• Ecto query timing visibility
• Oban queue and failure metrics
• End-to-end trace propagation where available

Step 3: Correlate

Ensure shared IDs across logs/metrics/traces for the same request or job.

Step 4: Alert and Dashboard

Create:

• Actionable alerts on user-facing SLO breaches
• Dashboard sections by surface (HTTP, LiveView, DB, jobs)
• Runbook pointers for each alert condition

Output Expectations

Return:

• Missing instrumentation by flow
• Proposed metrics and alert thresholds
• Dashboard layout recommendation
• Explicit implementation order