fix: host imports running a defaults pass and metrics restart per host (#1384)

plugins/host-metrics/src/backend/index.ts

@@ -22,6 +22,8 @@ export interface MetricsViewersV1 {
   unregister: (hostId: number, viewerSessionId: string) => void;
 }
 
+const RETIME_DEBOUNCE_MS = 1000;
+
 export async function activate(ctx: PluginContext) {
   const log = createLogger(ctx.log);
   const repository = await createHostMetricsRepository(ctx.db);
@@ -73,7 +75,19 @@ export async function activate(ctx: PluginContext) {
     const { hostId } = payload as { hostId?: number };
     if (hostId) poller.hostKeyAccepted(hostId);
   });
-  ctx.settings.onChange("metricsInterval", () => void poller.retimeAll());
+  // An import writes this once per host, and each write restarted every
+  // polled host. One retime after the writes settle covers them all.
+  let retime: ReturnType<typeof setTimeout> | null = null;
+  ctx.settings.onChange("metricsInterval", () => {
+    if (retime) clearTimeout(retime);
+    retime = setTimeout(() => {
+      retime = null;
+      void poller.retimeAll();
+    }, RETIME_DEBOUNCE_MS);
+  });
+  ctx.disposables.add(() => {
+    if (retime) clearTimeout(retime);
+  });
 
   ctx.services.provide<MetricsViewersV1>("host-metrics.viewers", {
     register: async (hostId) => {

plugins/host-metrics/tests/backend/activate.test.ts

@@ -1,4 +1,4 @@
-import { afterEach, describe, expect, it } from "vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
 import express from "express";
 import {
   createMockCtx,
@@ -9,6 +9,7 @@ import { PluginCapabilityError } from "@termix/plugin-sdk/backend";
 import { activate } from "../../src/backend/index.js";
 import type { MetricsViewersV1 } from "../../src/backend/index.js";
 import { hostImportNormalizer } from "../../src/backend/host-import.js";
+import { MetricsPoller } from "../../src/backend/poller.js";
 import { manifest, pluginDir, startServer, type TestServer } from "./server";
 
 let db: TestDb | null = null;
@@ -117,4 +118,23 @@ describe("hostImportNormalizer", () => {
   it("writes nothing for a row without metrics settings", () => {
     expect(hostImportNormalizer({ name: "x" })).toBeNull();
   });
+
+  it("retimes once after a burst of interval writes", async () => {
+    server = await startServer();
+    const retime = vi
+      .spyOn(MetricsPoller.prototype, "retimeAll")
+      .mockResolvedValue();
+    vi.useFakeTimers();
+    try {
+      for (let hostId = 1; hostId <= 20; hostId++) {
+        await server.mock.ctx.settings.setHost(hostId, "metricsInterval", 30);
+      }
+      expect(retime).not.toHaveBeenCalled();
+      await vi.advanceTimersByTimeAsync(1500);
+      expect(retime).toHaveBeenCalledTimes(1);
+    } finally {
+      vi.useRealTimers();
+      retime.mockRestore();
+    }
+  });
 });