fix: authenticate unwatched hosts during the status probe (#1337)

With metrics enabled, the status probe left SSH authentication to the
metrics poll - which only runs while someone is viewing the host. An
unwatched host therefore never left "reachable", while a host with
metrics disabled (whose probe always authenticates) showed online. The
probe now authenticates whenever no metrics poll will.

src/backend/hosts/metrics/host-status.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it } from "vitest";
 import {
+  needsStatusPollAuthentication,
   statusAfterAuthentication,
   statusAfterReachabilityCheck,
 } from "./host-status.js";
@@ -21,4 +22,11 @@ describe("host availability status", () => {
     expect(statusAfterAuthentication(false, "online")).toBe("reachable");
     expect(statusAfterAuthentication(false, "offline")).toBe("offline");
   });
+
+  it("authenticates in the status probe unless a metrics poll will do it", () => {
+    expect(needsStatusPollAuthentication(false, false)).toBe(true);
+    expect(needsStatusPollAuthentication(false, true)).toBe(true);
+    expect(needsStatusPollAuthentication(true, false)).toBe(true);
+    expect(needsStatusPollAuthentication(true, true)).toBe(false);
+  });
 });

src/backend/hosts/metrics/host-status.ts

@@ -15,3 +15,18 @@ export function statusAfterAuthentication(
   if (authenticated) return "online";
   return current === "offline" ? "offline" : "reachable";
 }
+
+/**
+ * Whether the cheap status probe must also authenticate over SSH.
+ *
+ * "online" means authenticated, and normally the metrics poll proves that.
+ * That poll only runs while someone is viewing the host, so an unwatched host
+ * with metrics enabled would otherwise never leave "reachable" - while a host
+ * with metrics disabled, whose probe always authenticates, shows online.
+ */
+export function needsStatusPollAuthentication(
+  metricsEnabled: boolean,
+  hasViewers: boolean,
+): boolean {
+  return !metricsEnabled || !hasViewers;
+}

src/backend/hosts/metrics/index.ts

@@ -71,6 +71,7 @@ import {
 } from "./helpers.js";
 import {
   type HostStatus,
+  needsStatusPollAuthentication,
   statusAfterAuthentication,
   statusAfterReachabilityCheck,
 } from "./host-status.js";
@@ -581,7 +582,10 @@ class PollingManager {
       if (
         isOnline &&
         supportsMetrics(refreshedHost) &&
-        !config?.statsConfig.metricsEnabled
+        needsStatusPollAuthentication(
+          !!config?.statsConfig.metricsEnabled,
+          this.activeViewers.has(refreshedHost.id),
+        )
       ) {
         try {
           await withSshConnection(refreshedHost, async () => undefined);