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lguidolin/observability-and-slos

Use when adding logging, metrics, tracing, health checks, SLOs, or alerting — or when building a service surface that needs to be operable and debuggable. Keywords — structured logs, OpenTelemetry, correlation id, RED metrics, liveness, readiness, SLI, SLO, error budget, alerting.

Was ist observability-and-slos?

observability-and-slos is a Claude Code agent skill that use when adding logging, metrics, tracing, health checks, SLOs, or alerting — or when building a service surface that needs to be operable and debuggable. Keywords — structured logs, OpenTelemetry, correlation id, RED metrics, liveness, readiness, SLI, SLO, error budget, alerting.

Funktioniert mit~Claude Code~Codex CLI~Cursor
npx skills add https://github.com/lguidolin/agent-skills/tree/main/skills/observability-and-slos

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Dokumentation

Observability and SLOs

Overview

You cannot operate, debug, or improve what you cannot see. Observability is designed in, not bolted on after the first outage. The first question in every incident is "what changed and who is affected" — a system that can't answer it turns a five-minute fix into an archaeology dig.

The Principles (universal)

  • The three signals. Emit structured logs (machine-parseable, not free text), metrics (counts, rates, durations), and traces (a request's path across services). A request carries a correlation/trace id end to end.
  • Instrument the golden signals for every surface: rate, errors, duration (RED) per endpoint/operation, plus resource saturation. A new endpoint isn't "done" until it's observable.
  • Health is an endpoint, not a guess. Expose liveness ("am I running?") and readiness ("can I serve traffic?") as distinct checks.
  • Define SLOs for critical journeys, with SLIs that measure them and an error budget that makes reliability-vs-features an explicit, data-driven trade-off.
  • Alert on symptoms, not causes. Page when users are hurting (SLO burn, readiness failing), not on every internal blip. Every alert must be actionable — an alert nobody acts on trains people to ignore alerts.

The Mechanisms (this stack)

  • Structured JSON logs to stdout, collected by the platform (e.g. AKS → Azure Monitor / Log Analytics). No free-text logging in services.
  • OpenTelemetry in the app server and PostGraphile; export traces/metrics to Azure Monitor / Application Insights (or Prometheus/Grafana).
  • Correlation id propagated across the data path — generated at the edge, passed Browser → App → PostGraphile alongside context headers, attached to every log line and span.
  • RED metrics per HTTP route and GraphQL operation; Postgres slow-query log + pg_stat_statements.
  • Liveness/readiness endpoints wired to Kubernetes probes (see cloud-delivery-aks). Readiness reflects real dependency health (can it reach the DB?), not just process-up.
  • Frontend: report web-vitals and client errors to the same backend.
  • SLOs per journey with dashboards and burn-rate alerts.

When to scale this

A pre-launch/local project implements structured logs + health endpoints now and defers SLOs/alerting until there are real users to protect. State the mode in the first decision record.

Full rationale: Articles IX & XVI of the constitution, bundled at engineering-constitution/references/engineering-constitution.md.

Individual skills in this repo

This repo contains 18 individual skills — each has its own dedicated page.

lguidolin/change-hygiene-and-code-craft

Use when writing or refactoring code, structuring a commit or PR, or deciding whether to abstract duplication. Symptoms — mixing reorg with logic changes, a PR doing several things at once, a file growing large, the second copy of similar code, or unsure whether to DRY something up.

lguidolin/cloud-delivery-aks

Use when deploying to Kubernetes or Azure Kubernetes Service (AKS), configuring cloud secrets, setting up progressive rollout/canary, per-PR ephemeral environments, or k8s health probes. Keywords — Kubernetes, AKS, Key Vault, Argo Rollouts, Flagger, canary, blue-green, liveness, readiness, PodDisruptionBudget, HPA, rollback, GHCR.

lguidolin/commit-history-rewrite

Use when an existing repository has messy commit history that needs to conform to conventional commits before adopting release-please, or when intermediate WIP/fixup/merge commits need to be cleaned up.

lguidolin/conventional-commits-and-releases

Use when committing, writing a commit message, opening a PR that will be squash-merged, or configuring automated versioning/changelogs. Keywords — conventional commits, release-please, semver, feat/fix/chore, breaking change, changelog.

lguidolin/defense-in-depth-security

Use when handling untrusted input, secrets, authentication/authorization, or dependencies — or threat-modeling a new surface. Keywords — STRIDE, threat model, least privilege, secrets management, supply chain, dependency scanning, input validation, audit log, defense in depth.

lguidolin/designing-before-building

Use when starting a feature, fixing a non-trivial bug, or about to write implementation code — before any code exists. Symptoms you need this: "this is simple, I'll just code it", reaching for the editor before a design is approved, or an idea that hasn't been turned into a spec and plan.

lguidolin/engineering-constitution

Use when starting work in a project that follows the engineering constitution, orienting to its rules, or deciding which engineering practice applies to a task — spec writing, commits, testing, security, deploys, database, or UI work.

lguidolin/graphql-contract-testing

Use when writing a GraphQL query/mutation that the UI and a test will share, or building route/schema contract or smoke tests. Symptoms — copying a query into a test, a test asserting on query text, schema change that didn't break the UI build, or RLS/permission drift. Keywords — graphql-codegen, typed document, contract test, route smoke test.

lguidolin/init-repo-CI

Use when setting up a new repository with conventional commits, release-please, and CI automation, or when retrofitting an existing repository that lacks automated versioning and PR validation workflows.

lguidolin/interface-craft-and-accessibility

Use when building or styling UI — components, layouts, forms, design tokens — or making accessibility decisions. Keywords — a11y, WCAG, keyboard navigation, focus state, contrast, design system, minimalist UI, component reuse, ARIA, semantic HTML.

lguidolin/merge-gates-and-automation

Use when setting up or changing CI, pre-push hooks, or a task runner, or deciding what must pass before merge. Symptoms — tempted to put authoritative checks only in a local hook, skip CI, bypass with --no-verify, or unsure what gates a merge vs. runs locally.

lguidolin/performance-and-scale

Use when working on hot paths, list endpoints, pagination, data-access in loops, or public interfaces/schemas. Symptoms — unbounded queries, N+1 access, no latency budget, optimizing without measuring, or changing an interface many consumers depend on. Keywords — pagination, N+1, Hyrum's Law, performance budget, bundle size.

lguidolin/postgres-postgraphile-rls-and-sql

Use when writing PostgreSQL, PostGraphile config, Row-Level Security policies, SQL schema files, or working on the Browser→App→PostGraphile→Postgres data path. Keywords — RLS, SECURITY DEFINER, search_path, pgSettings, grants, roles, GraphQL depth limit, query cost, statement_timeout, SQL file organization.

lguidolin/recording-decisions

Use when a design or architecture decision has been made and needs to be captured — writing a decision record or ADR, updating a decision index, noting a deferred idea, or superseding a past decision. Keywords — ADR, decision record, rationale, rejected alternatives, dependency index.

lguidolin/resilience-and-deploy-safety

Use when planning a deploy, designing a rollback, or responding to an incident or writing a postmortem. Keywords — deploy safety, rollback, immutable artifact, progressive delivery, canary, blast radius, incident response, blameless postmortem, error budget.

lguidolin/ship-it

Use when the user wants to ship work — push, PR, archive decision records, merge, and clean up. Handles the full lifecycle from committing final changes through post-merge cleanup including converting specs/plans to compact decision records.

lguidolin/tests-as-a-control

Use when writing or modifying tests, when a test breaks during a refactor, or when testing permission/role rules. Symptoms — tempted to edit a test to make it pass, testing only the happy path, a deny-test that started passing, flaky tests, or unsure what to assert.

lguidolin/zero-downtime-migrations

Use when changing a database schema where data must survive the change — adding/removing/renaming columns, constraints, indexes, or backfilling. Symptoms — a destructive migration bundled with a code deploy, a NOT NULL column with a backfill, a table-locking UPDATE, or a rename. Keywords — expand/contract, parallel change, backfill, NOT VALID, CREATE INDEX CONCURRENTLY, graphile-migrate.

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