app/lib/health/snapshot.server.ts

Functions

Imports

It imports app/lib/error-message.mjs, app/lib/health/snapshot.mjs. Imported by app/routes/api.health.ts, app/routes/colophon.tsx.

Source

1// A reader that could write would turn a cache miss on the busiest page back into a health run.
2
3import {
4  HEALTH_SNAPSHOT_KEY,
5  healthTile,
6  snapshotFromBody,
7  type HealthTile,
8} from "./snapshot.mjs";
9import { errorMessage } from "~/lib/error-message.mjs";
10
11/**
12 * Never throws: bookkeeping must not cost the health endpoint its verdict. Awaited, not waitUntil, so
13 * a caller reading this then the home page sees a consistent pair. No expiry: an aging "stale" beats
14 * a "missing" that reads as misconfiguration.
15 */
16export async function writeHealthSnapshot(
17  env: Env,
18  body: { ok: boolean; checks: Array<{ ok: boolean }> },
19  readAt: string,
20): Promise<void> {
21  try {
22    await env.APP_KV.put(HEALTH_SNAPSHOT_KEY, JSON.stringify(snapshotFromBody(body, readAt)));
23  } catch (error) {
24    /* A snapshot write must never cost the caller their health verdict, but it is logged: an
25     * unwritten snapshot ages the tile to "stale" and reads as a dead watchdog. */
26    console.error(
27      JSON.stringify({
28        alert: "health-snapshot-write-failed",
29        detail: errorMessage(error),
30      }),
31    );
32  }
33}
34
35/**
36 * A throw renders as `unreadable`, never as `missing`: the home page must render whatever KV is doing,
37 * but a failed read is not the same fact as no snapshot having been written. It is logged.
38 */
39export async function readHealthTile(env: Env): Promise<HealthTile> {
40  let stored: unknown;
41  try {
42    stored = await env.APP_KV.get(HEALTH_SNAPSHOT_KEY, "json");
43  } catch (error) {
44    console.error(
45      JSON.stringify({
46        alert: "health-snapshot-read-failed",
47        detail: errorMessage(error),
48      }),
49    );
50    return { state: "unreadable" };
51  }
52  return healthTile(stored, Date.now());
53}