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Rollup status

Overall HealthResponse.status is computed from all check results for that probe:
  1. Any fail → fail (unless remapped by onFail.treatAs on that check).
  2. Else any degraded → degraded.
  3. Else ok.
Override with rollup.computeStatus(results) for custom rules.

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HTTP status

Response status (HTTP code) is derived from the rolled-up health status and your config:
  • Any check with status === "fail" and onFail.httpStatus set → that value is returned (first matching check in config order wins among failed checks with a custom status).
  • Else if rollup is fail: defaults.onFail.httpStatus or 503.
  • Else if rollup is degraded: defaults.onDegraded.httpStatus or 200.
  • Else 200.
onFail.treatAs changes the check status used for rollup and the JSON/text body; combine with onFail.httpStatus or defaults when you need a specific HTTP code.

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Output

output on the root config:
  • format: "json" (default) or "text".
    • JSON: Content-Type: application/json, body is JSON.stringify of HealthResponse.
    • Text: Content-Type: text/plain, human-readable lines (status:, then each check with latency and optional error).
  • exposeError: Default true. If false, the error field is omitted from each check in the payload.

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Public API overview

Runtime
  • createHealthKit(config) → HealthKit
  • HealthKit: start(), stop(), handleRequest(req), handleLiveness(), handleReadiness()
  • toFetchResponse(res, method?) → Fetch Response (HEAD omits the body)
  • createFetchHandler(kit) → (request: Request) => Promise<Response> for Deno, Bun, and Workers
Types
  • HealthkitConfig, CheckConfig, HealthAdapter, AdapterResult, CheckResult, HealthResponse
  • CheckStatus, CheckType, RollupConfig, OutputConfig, DefaultsConfig
  • AgnosticRequest, AgnosticResponse
The canonical type definitions and any future additions live in the healthzkit package under packages/healthzkit in this monorepo.