33 lines
2.9 KiB
Markdown
33 lines
2.9 KiB
Markdown
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# Changelog
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All notable changes to this module will be documented in this file.
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The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
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and this module adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
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## [0.9.0] - 2026-03-18
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### Added
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- `Level` type — `int` representing component criticality; zero value is `LevelCritical`
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- `LevelCritical` constant (value `0`) — a failing critical component sets overall status to `DOWN` and returns HTTP 503
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- `LevelDegraded` constant (value `1`) — a failing degraded component sets overall status to `DEGRADED` and returns HTTP 200
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- `Checkable` interface — `HealthCheck(ctx context.Context) error`, `Name() string`, `Priority() Level`; implemented by infrastructure components
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- `Logger` interface — duck-typed minimal logger (`Debug`, `Info`, `Warn`, `Error`, `WithContext`) satisfied by `logz.Logger` without importing logz
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- `ComponentStatus` struct — JSON-serialisable per-component result with fields `status string`, `latency string` (omitempty), and `error string` (omitempty)
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- `Response` struct — JSON-serialisable overall response with fields `status string` and `components map[string]ComponentStatus`
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- `NewHandler(logger Logger, checks ...Checkable) http.Handler` — constructs an `http.Handler` that runs all registered checks concurrently, collects results via a buffered channel, and writes a JSON `Response`
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- Parallel check execution: each `Checkable.HealthCheck` call runs in its own goroutine; a buffered channel sized to the check count prevents goroutine leaks
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- Per-request 5-second deadline derived from `context.WithTimeout(r.Context(), 5*time.Second)` and propagated to all check goroutines
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- Overall status aggregation: `UP` if all checks pass; `DEGRADED` (HTTP 200) if at least one degraded component fails and no critical component fails; `DOWN` (HTTP 503) if any critical component fails
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- Check latency measurement: each goroutine records `time.Since(start)` and includes it as a string in `ComponentStatus`
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- `Content-Type: application/json` response header set on every response
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### Design Notes
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- All checks run in parallel goroutines and report through a buffered channel; the buffer is sized exactly to the number of registered checks at construction time, so the handler is guaranteed to drain all results without blocking even if it returns early.
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- The two-level criticality model (`LevelCritical` / `LevelDegraded`) gives orchestrators and load balancers a clean binary HTTP signal (200 vs 503) while still surfacing partial degradation in the JSON body for monitoring systems.
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- The `Logger` and `Checkable` interfaces are defined entirely within this package using duck typing — no micro-lib module is imported, keeping `health` a pure stdlib package (Tier 0/1) that infra packages can satisfy without a circular dependency.
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[0.9.0]: https://code.nochebuena.dev/go/health/releases/tag/v0.9.0
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