feat(swingset): configurable snapshotPruneInterval (=20)

Pruning snapshots involves an O(n) query on the DB, so doing it on every crank seems expensive. refs #3374
Agoric · Jul 21, 2021 · 44b2693 · 44b2693
1 parent c792d81
commit 44b2693
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Showing 3 changed files with 17 additions and 4 deletions.
diff --git a/packages/SwingSet/src/kernel/kernel.js b/packages/SwingSet/src/kernel/kernel.js
@@ -707,7 +707,7 @@ export default function buildKernel(
       kernelKeeper.incrementCrankNumber();
       if (snapStore) {
         // eslint-disable-next-line no-use-before-define
-        vatWarehouse.pruneSnapshots(snapStore);
+        vatWarehouse.pruneSnapshots(snapStore, kernelKeeper.getCrankNumber());
       }
     } finally {
       processQueueRunning = undefined;

diff --git a/packages/SwingSet/src/kernel/vatManager/vat-warehouse.js b/packages/SwingSet/src/kernel/vatManager/vat-warehouse.js
@@ -49,6 +49,7 @@ export const makeLRU = max => {
  *   maxVatsOnline?: number,
  *   snapshotInitial?: number,
  *   snapshotInterval?: number,
+ *   snapshotPruneInverval?: number,
  * }=} policyOptions
  *
  * @typedef {(syscall: VatSyscallObject) => ['error', string] | ['ok', null] | ['ok', Capdata]} VatSyscallHandler
@@ -66,6 +67,7 @@ export function makeVatWarehouse(kernelKeeper, vatLoader, policyOptions) {
     // Note: some measurements show 10 deliveries per sec on XS
     //       as of this writing.
     snapshotInterval = 200,
+    snapshotPruneInterval = 20,
   } = policyOptions || {};
   // Idea: snapshot based on delivery size: after deliveries >10Kb.
   // console.debug('makeVatWarehouse', { policyOptions });
@@ -302,16 +304,23 @@ export function makeVatWarehouse(kernelKeeper, vatLoader, policyOptions) {
     return true;
   }
 
+  const snapshotPruneIntervalBI = BigInt(snapshotPruneInterval);
+
   /**
-   * Delete unused snapshots.
+   * Delete unused snapshots periodically.
    *
    * WARNING: caller is responsible to call this only
    * when all records of snapshot consumers are durably
    * stored; for example, after commitCrank().
    *
    * @param { SnapStore } snapStore
+   * @param { bigint } crankNumber
    */
-  function pruneSnapshots(snapStore) {
+  function pruneSnapshots(snapStore, crankNumber) {
+    if (crankNumber % snapshotPruneIntervalBI !== 0n) {
+      return;
+    }
+
     const todo = kernelKeeper.getUnusedSnapshots();
     const done = [];
     for (const snapshotID of todo) {

diff --git a/packages/SwingSet/test/vat-warehouse/test-warehouse.js b/packages/SwingSet/test/vat-warehouse/test-warehouse.js
@@ -132,7 +132,11 @@ test('snapshot after deliveries', async t => {
   const hostStorage = { snapStore, ...provideHostStorage() };
   const c = await makeController('xs-worker', {
     hostStorage,
-    warehousePolicy: { maxVatsOnline, snapshotInterval: 1 },
+    warehousePolicy: {
+      maxVatsOnline,
+      snapshotInterval: 1,
+      snapshotPruneInterval: 1,
+    },
   });
   t.teardown(c.shutdown);