fix(docker): healthcheck tries 127.0.0.1/localhost/::1 and surfaces errors (#3151) (#3209)

The healthcheck probed only 127.0.0.1 and swallowed every error (empty
Output), so containers binding to a non-loopback address always reported
unhealthy with no diagnostic. Add a multi-host probe helper that succeeds on
the first 2xx and prints the last error to stderr on total failure.

Co-authored-by: naimo84 <naimo84@users.noreply.github.com>

scripts/dev/healthcheck.mjs

@@ -2,13 +2,83 @@
 
 /**
  * Docker healthcheck script for OmniRoute.
- * Checks the /api/monitoring/health endpoint on the dashboard port.
+ * Probes the /api/monitoring/health endpoint on the dashboard port.
  * Used by Dockerfile and docker-compose files.
+ *
+ * #3151 — in some Docker network setups the server binds to a container IP and
+ * a probe against `127.0.0.1` is not reachable, while `localhost`/`::1` (or vice
+ * versa) is. The previous version probed ONLY `127.0.0.1` and swallowed every
+ * error, so the container was reported `unhealthy` with an empty, undiagnosable
+ * `State.Health[].Output`. We now try an ordered list of hosts and surface the
+ * last error on total failure.
  */
-const port = process.env.DASHBOARD_PORT || process.env.PORT || "20128";
 
-fetch(`http://127.0.0.1:${port}/api/monitoring/health`)
-  .then((r) => {
-    if (!r.ok) throw new Error(`HTTP ${r.status}`);
-  })
-  .catch(() => process.exit(1));
+import { pathToFileURL } from "node:url";
+
+const DEFAULT_HOSTS = ["127.0.0.1", "localhost", "::1"];
+const DEFAULT_TIMEOUT_MS = 4000;
+
+/**
+ * Build the health URL for a host, bracketing IPv6 literals (e.g. `::1`).
+ * @param {string} host
+ * @param {string|number} port
+ */
+function healthUrl(host, port) {
+  const hostPart = host.includes(":") ? `[${host}]` : host;
+  return `http://${hostPart}:${port}/api/monitoring/health`;
+}
+
+/**
+ * Probe the health endpoint across an ordered list of hosts. Resolves with the
+ * first host that returns a 2xx response; rejects with the last error if every
+ * host fails. Each attempt is bounded by a per-host timeout so one unreachable
+ * host cannot hang the whole probe.
+ *
+ * @param {object} opts
+ * @param {string|number} opts.port
+ * @param {string[]} [opts.hosts]
+ * @param {typeof fetch} [opts.fetchImpl]
+ * @param {number} [opts.timeoutMs]
+ * @returns {Promise<string>} the host that succeeded
+ */
+export async function probeHealth({
+  port,
+  hosts = DEFAULT_HOSTS,
+  fetchImpl = fetch,
+  timeoutMs = DEFAULT_TIMEOUT_MS,
+} = {}) {
+  let lastError = new Error("no hosts to probe");
+  for (const host of hosts) {
+    try {
+      const res = await fetchImpl(healthUrl(host, port), {
+        signal: AbortSignal.timeout(timeoutMs),
+      });
+      if (res.ok) return host;
+      lastError = new Error(`${host}: HTTP ${res.status}`);
+    } catch (err) {
+      lastError = new Error(`${host}: ${err instanceof Error ? err.message : String(err)}`);
+    }
+  }
+  throw lastError;
+}
+
+async function main() {
+  const port = process.env.DASHBOARD_PORT || process.env.PORT || "20128";
+  try {
+    await probeHealth({ port });
+    process.exit(0);
+  } catch (err) {
+    // Surface the failure so `docker inspect ... .State.Health[].Output` is
+    // diagnostic instead of empty (#3151).
+    process.stderr.write(`healthcheck failed: ${err instanceof Error ? err.message : err}\n`);
+    process.exit(1);
+  }
+}
+
+// Only auto-run when invoked as the entrypoint (so importing the helper in
+// tests does not trigger a real probe + process.exit).
+const isEntrypoint =
+  Boolean(process.argv[1]) && import.meta.url === pathToFileURL(process.argv[1]).href;
+if (isEntrypoint) {
+  main();
+}