fix(database): batch database saves for bulk host writes (#1554)

* fix(database): yield to the event loop between database saves

Each SQLite save serializes and encrypts the whole database into new
buffers, which V8 only releases once the event loop turns. Boot
migrations and bulk host import write plugin settings per host and per
key in an awaited loop, so hundreds of full copies piled up and the
container ran out of memory.

* fix(database): save once per bulk host write instead of once per row

On SQLite every repository write force-saves the whole database. Boot
plugin data migrations, host defaults materialization and the bulk
host routes write one row per host per setting, so they serialized and
encrypted the full database hundreds of times in a row.

DatabaseSaveTrigger.batched wraps a function so force saves made while
it runs collapse into a single save when it finishes. Nested scopes fold
into the outer one, and work that outlives its scope saves normally.

src/backend/hosts/defaults/materialize.ts

@@ -30,6 +30,7 @@ import {
 import { hostSettingsPlugins } from "../../database/routes/host-plugin-settings.js";
 import { notifySettingChange } from "../../plugins/settings.js";
 import { databaseLogger } from "../../utils/logger.js";
+import { DatabaseSaveTrigger } from "../../utils/database-save-trigger.js";
 import {
   buildCatalog,
   catalogNamespaces,
@@ -342,83 +343,85 @@ async function afterHostsChanged(
  * Classifies and rewrites a set of hosts. Returns the hosts whose values or
  * overrides changed; with `dryRun` nothing is written.
  */
-export async function materializeHosts(
-  target: HostDefaultsTarget,
-  options: MaterializeOptions = {},
-): Promise<MaterializeResult> {
-  const repository = createCurrentHostDefaultsRepository();
-  const rows = (await repository.listHosts(target)).filter(
-    // A desktop's read-only copy of a shared host follows its owner's server.
-    (row) => !row.sharedSource,
-  );
-  if (rows.length === 0) return { changedHostIds: [] };
-
-  const { catalog } = currentCatalog();
-  const userIds = [...new Set(rows.map((row) => row.userId))];
-  const [index, placement, pluginRows] = await Promise.all([
-    loadDefaultsIndex(userIds),
-    loadPlacement(userIds),
-    loadPluginRows(rows.map((row) => row.id)),
-  ]);
-  const withOverlay = applyOverlay(index, options.overlay);
-
-  const changed: Array<{ row: HostRow; plan: HostPlan }> = [];
-  for (const row of rows) {
-    const levels = levelsForHost(
-      withOverlay,
-      row.userId,
-      effectiveFolderPath(row.id, placement),
+export const materializeHosts = DatabaseSaveTrigger.batched(
+  async (
+    target: HostDefaultsTarget,
+    options: MaterializeOptions = {},
+  ): Promise<MaterializeResult> => {
+    const repository = createCurrentHostDefaultsRepository();
+    const rows = (await repository.listHosts(target)).filter(
+      // A desktop's read-only copy of a shared host follows its owner's server.
+      (row) => !row.sharedSource,
     );
-    const plan = planHost(row, levels, catalog, pluginRows.get(row.id), {
-      keys: options.keys,
-    });
-    const valuesChanged =
-      Object.keys(plan.columns).some((key) => key !== "defaultOverrides") ||
-      plan.pluginWrites.length > 0;
-    if (options.dryRun) {
-      if (valuesChanged) changed.push({ row, plan });
-      continue;
+    if (rows.length === 0) return { changedHostIds: [] };
+
+    const { catalog } = currentCatalog();
+    const userIds = [...new Set(rows.map((row) => row.userId))];
+    const [index, placement, pluginRows] = await Promise.all([
+      loadDefaultsIndex(userIds),
+      loadPlacement(userIds),
+      loadPluginRows(rows.map((row) => row.id)),
+    ]);
+    const withOverlay = applyOverlay(index, options.overlay);
+
+    const changed: Array<{ row: HostRow; plan: HostPlan }> = [];
+    for (const row of rows) {
+      const levels = levelsForHost(
+        withOverlay,
+        row.userId,
+        effectiveFolderPath(row.id, placement),
+      );
+      const plan = planHost(row, levels, catalog, pluginRows.get(row.id), {
+        keys: options.keys,
+      });
+      const valuesChanged =
+        Object.keys(plan.columns).some((key) => key !== "defaultOverrides") ||
+        plan.pluginWrites.length > 0;
+      if (options.dryRun) {
+        if (valuesChanged) changed.push({ row, plan });
+        continue;
+      }
+      if (valuesChanged || plan.overridesChanged) changed.push({ row, plan });
     }
-    if (valuesChanged || plan.overridesChanged) changed.push({ row, plan });
-  }
 
-  if (options.dryRun) {
-    return { changedHostIds: changed.map(({ row }) => row.id) };
-  }
+    if (options.dryRun) {
+      return { changedHostIds: changed.map(({ row }) => row.id) };
+    }
 
-  await repository.updateHosts(
-    changed.map(({ row, plan }) => ({
-      id: row.id,
-      values: plan.columns as Partial<HostRow>,
-    })),
-  );
-  const settings = createCurrentPluginSettingsRepository();
-  for (const { plan } of changed) {
-    for (const write of plan.pluginWrites) {
-      if (write.value === undefined) {
-        await settings.delete(
-          write.pluginId,
-          "host",
-          String(write.hostId),
-          write.key,
-        );
-      } else {
-        await settings.set(
-          write.pluginId,
-          "host",
-          String(write.hostId),
-          write.key,
-          JSON.stringify(write.value),
-        );
+    await repository.updateHosts(
+      changed.map(({ row, plan }) => ({
+        id: row.id,
+        values: plan.columns as Partial<HostRow>,
+      })),
+    );
+    const settings = createCurrentPluginSettingsRepository();
+    for (const { plan } of changed) {
+      for (const write of plan.pluginWrites) {
+        if (write.value === undefined) {
+          await settings.delete(
+            write.pluginId,
+            "host",
+            String(write.hostId),
+            write.key,
+          );
+        } else {
+          await settings.set(
+            write.pluginId,
+            "host",
+            String(write.hostId),
+            write.key,
+            JSON.stringify(write.value),
+          );
+        }
       }
     }
-  }
 
-  const valueChanges = changed.filter(
-    ({ plan }) =>
-      plan.pluginWrites.length > 0 ||
-      Object.keys(plan.columns).some((key) => key !== "defaultOverrides"),
-  );
-  await afterHostsChanged(valueChanges);
-  return { changedHostIds: valueChanges.map(({ row }) => row.id) };
-}
+    const valueChanges = changed.filter(
+      ({ plan }) =>
+        plan.pluginWrites.length > 0 ||
+        Object.keys(plan.columns).some((key) => key !== "defaultOverrides"),
+    );
+    await afterHostsChanged(valueChanges);
+    return { changedHostIds: valueChanges.map(({ row }) => row.id) };
+  },
+);