monitor.component-state

export function componentState(statuses: readonly CheckStatus[], underMaintenance: boolean): ComponentState

export type ComponentState = "operational" | "degraded" | "partial-outage" | "major-outage" | "maintenance";

import { componentState } from "#fune/monitor.component-state@^1";

import { type CheckStatus } from "./monitor_check_status.ts";  ← from monitor.check-status ^1.0.0 · built alongside by fune
import { type ComponentState } from "./monitor_component_state_types.ts";

/**
 * One component's state in Atlassian Statuspage's vocabulary. Maintenance
 * wins, so planned work never pages anyone as an outage; the statuses are
 * still checked, so a bad feed fails loudly even during maintenance.
 */
export function componentState(statuses: readonly CheckStatus[], underMaintenance: boolean): ComponentState {
  if (statuses.length === 0) throw new RangeError("statuses must not be empty");
  if (typeof underMaintenance !== "boolean") throw new TypeError("underMaintenance must be true or false");
  let down = 0;
  let degraded = 0;
  for (const s of statuses) {
    if (s === "down") down += 1;
    else if (s === "degraded") degraded += 1;
    else if (s !== "up") throw new RangeError(`unknown check status: ${String(s)}`);
  }
  if (underMaintenance) return "maintenance";
  if (down === statuses.length) return "major-outage";
  if (down > 0) return "partial-outage";
  return degraded > 0 ? "degraded" : "operational";
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and its 1 dependency, pins them in fune.lock, downloads only the TypeScript package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add monitor.component-state

The manifest, vectors and README with only the TypeScript implementation. Install it without the registry with fune add ./monitor.component-state-1.0.0-typescript.fune, or fetch it from a terminal with fune pull monitor.component-state@1.0.0:typescript.

The whole function, every language, is one file too: monitor.component-state-1.0.0.fune, 9,719 bytes, sha256 cffd933922c240ddf102b7ac117550f261e261ec98c4c1781338eee2a23942d6. It installs into a project of any language.

// fune: before monitor.component-state

// fune: after monitor.component-state

// fune: replace monitor.check-status in monitor.component-state

// fune: step monitor.component-state after <n|label>

More from the author

The values here are kebab-case like the rest of the registry's enums; map them to Statuspage's snake_case when calling its API.

## The rule, in order

1. `underMaintenance` is true: **maintenance**. Planned work is announced as such, not reported as an outage. 2. Every check down: **major-outage**. So a component with one check that is down is a major outage, not a partial one. 3. Some checks down: **partial-outage**. 4. Any check degraded: **degraded**. Degraded checks never add up to an outage. 5. Otherwise **operational**.

The statuses are validated even under maintenance, so a broken feed fails loudly instead of hiding behind a maintenance window. To decide whether a maintenance window is active, see `monitor.maintenance-window`; to combine one target's probe locations into a single status first, `monitor.check-status`.

## Errors

- `statuses must not be empty`: a component with no checks has no state. - `unknown check status: X` - `underMaintenance must be true or false`

## Sources

- Atlassian Support, "Show service status with components": https://support.atlassian.com/statuspage/docs/show-service-status-with-components/ (the five component statuses: Operational, Degraded performance, Partial outage, Major outage, Under maintenance). - Statuspage Status API (component `status` values `operational`, `degraded_performance`, `partial_outage`, `major_outage`): https://metastatuspage.com/api

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