feat: relocate snapshot metadata from kvStore to snapStore

Closes #6742

Author: FUDCo

packages/SwingSet/src/controller/controller.js

@@ -115,21 +115,23 @@ export function makeStartXSnap(bundles, { snapStore, env, spawn }) {
   }
 
   /**
+   * @param {string} vatID
    * @param {string} name
    * @param {(request: Uint8Array) => Promise<Uint8Array>} handleCommand
    * @param {boolean} [metered]
-   * @param {string} [snapshotHash]
+   * @param {boolean} [reload]
    */
   async function startXSnap(
+    vatID,
     name,
     handleCommand,
     metered,
-    snapshotHash = undefined,
+    reload = false,
   ) {
     const meterOpts = metered ? {} : { meteringLimit: 0 };
-    if (snapStore && snapshotHash) {
+    if (snapStore && reload) {
       // console.log('startXSnap from', { snapshotHash });
-      return snapStore.load(snapshotHash, async snapshot => {
+      return snapStore.loadSnapshot(vatID, async snapshot => {
         const xs = doXSnap({
           snapshot,
           name,

packages/SwingSet/src/kernel/state/kernelKeeper.js

@@ -89,8 +89,7 @@ const enableKernelGC = true;
 // v$NN.reapInterval = $NN or 'never'
 // v$NN.reapCountdown = $NN or 'never'
 // exclude from consensus
-// local.v$NN.lastSnapshot = JSON({ snapshotID, startPos })
-// local.snapshot.$id = [vatID, ...]
+// local.*
 
 // m$NN.remaining = $NN // remaining capacity (in computrons) or 'unlimited'
 // m$NN.threshold = $NN // notify when .remaining first drops below this
@@ -786,10 +785,7 @@ export default function makeKernelKeeper(kernelStorage, kernelSlog) {
     const promisePrefix = `${vatID}.c.p`;
     const kernelPromisesToReject = [];
 
-    const old = vatKeeper.getLastSnapshot();
-    if (old) {
-      vatKeeper.removeFromSnapshot(old.snapshotID);
-    }
+    vatKeeper.deleteSnapshots();
 
     // Note: ASCII order is "+,-./", and we rely upon this to split the
     // keyspace into the various o+NN/o-NN/etc spaces. If we were using a

packages/SwingSet/src/kernel/state/vatKeeper.js

@@ -45,14 +45,8 @@ export function initializeVatState(kvStore, streamStore, vatID) {
   kvStore.set(`${vatID}.d.nextID`, `${FIRST_DEVICE_ID}`);
   kvStore.set(`${vatID}.nextDeliveryNum`, `0`);
   kvStore.set(`${vatID}.incarnationNumber`, `1`);
-  kvStore.set(
-    `${vatID}.t.startPosition`,
-    `${JSON.stringify(streamStore.STREAM_START)}`,
-  );
-  kvStore.set(
-    `${vatID}.t.endPosition`,
-    `${JSON.stringify(streamStore.STREAM_START)}`,
-  );
+  kvStore.set(`${vatID}.t.startPosition`, `${streamStore.STREAM_START}`);
+  kvStore.set(`${vatID}.t.endPosition`, `${streamStore.STREAM_START}`);
 }
 
 /**
@@ -486,9 +480,9 @@ export function makeVatKeeper(
    */
   function* getTranscript(startPos) {
     if (startPos === undefined) {
-      startPos = JSON.parse(getRequired(`${vatID}.t.startPosition`));
+      startPos = Number(getRequired(`${vatID}.t.startPosition`));
     }
-    const endPos = JSON.parse(getRequired(`${vatID}.t.endPosition`));
+    const endPos = Number(getRequired(`${vatID}.t.endPosition`));
     for (const entry of streamStore.readStream(
       transcriptStream,
       /** @type { StreamPosition } */ (startPos),
@@ -504,88 +498,34 @@ export function makeVatKeeper(
    * @param {object} entry  The transcript entry to append.
    */
   function addToTranscript(entry) {
-    const oldPos = JSON.parse(getRequired(`${vatID}.t.endPosition`));
+    const oldPos = Number(getRequired(`${vatID}.t.endPosition`));
     const newPos = streamStore.writeStreamItem(
       transcriptStream,
       JSON.stringify(entry),
       oldPos,
     );
-    kvStore.set(`${vatID}.t.endPosition`, `${JSON.stringify(newPos)}`);
+    kvStore.set(`${vatID}.t.endPosition`, `${newPos}`);
   }
 
   /** @returns {StreamPosition} */
   function getTranscriptEndPosition() {
-    return JSON.parse(
+    const endPosition =
       kvStore.get(`${vatID}.t.endPosition`) ||
-        assert.fail('missing endPosition'),
-    );
+      assert.fail('missing endPosition');
+    return Number(endPosition);
   }
 
-  /**
-   * @returns {{ snapshotID: string, startPos: StreamPosition } | undefined}
-   */
-  function getLastSnapshot() {
-    const notation = kvStore.get(`local.${vatID}.lastSnapshot`);
-    if (!notation) {
-      return undefined;
-    }
-    const { snapshotID, startPos } = JSON.parse(notation);
-    assert.typeof(snapshotID, 'string');
-    assert(startPos);
-    return { snapshotID, startPos };
+  function getSnapshotInfo() {
+    return snapStore?.getSnapshotInfo(vatID);
   }
 
   function transcriptSnapshotStats() {
     const totalEntries = getTranscriptEndPosition();
-    const lastSnapshot = getLastSnapshot();
-    const snapshottedEntries = lastSnapshot ? lastSnapshot.startPos : 0;
+    const snapshotInfo = getSnapshotInfo();
+    const snapshottedEntries = snapshotInfo ? snapshotInfo.endPos : 0;
     return { totalEntries, snapshottedEntries };
   }
 
-  /**
-   * Add vatID to consumers of a snapshot.
-   *
-   * @param {string} snapshotID
-   */
-  function addToSnapshot(snapshotID) {
-    const key = `local.snapshot.${snapshotID}`;
-    const consumers = JSON.parse(kvStore.get(key) || '[]');
-    assert(Array.isArray(consumers));
-
-    // We can't completely rule out the possibility that
-    // a vat will use the same snapshot twice in a row.
-    //
-    // PERFORMANCE NOTE: we assume consumer lists are short;
-    // usually length 1. So O(n) search here is better
-    // than keeping the list sorted.
-    if (!consumers.includes(vatID)) {
-      consumers.push(vatID);
-      kvStore.set(key, JSON.stringify(consumers));
-      // console.log('addToSnapshot result:', { vatID, snapshotID, consumers });
-    }
-  }
-
-  /**
-   * Remove vatID from consumers of a snapshot.
-   *
-   * @param {string} snapshotID
-   */
-  function removeFromSnapshot(snapshotID) {
-    const key = `local.snapshot.${snapshotID}`;
-    const consumersJSON = kvStore.get(key);
-    if (!consumersJSON) {
-      throw Fail`cannot remove ${vatID}: ${key} key not defined`;
-    }
-    const consumers = JSON.parse(consumersJSON);
-    assert(Array.isArray(consumers));
-    const ix = consumers.indexOf(vatID);
-    assert(ix >= 0);
-    consumers.splice(ix, 1);
-    // console.log('removeFromSnapshot done:', { vatID, snapshotID, consumers });
-    kvStore.set(key, JSON.stringify(consumers));
-    return consumers.length;
-  }
-
   /**
    * Store a snapshot, if given a snapStore.
    *
@@ -597,30 +537,19 @@ export function makeVatKeeper(
       return false;
     }
 
-    const info = await manager.makeSnapshot(snapStore);
+    const endPosition = getTranscriptEndPosition();
+    const info = await manager.makeSnapshot(endPosition, snapStore);
     const {
-      hash: snapshotID,
+      hash,
       rawByteCount,
       rawSaveSeconds,
       compressedByteCount,
       compressSeconds,
     } = info;
-    const old = getLastSnapshot();
-    if (old && old.snapshotID !== snapshotID) {
-      if (removeFromSnapshot(old.snapshotID) === 0) {
-        snapStore.deleteSnapshot(old.snapshotID);
-      }
-    }
-    const endPosition = getTranscriptEndPosition();
-    kvStore.set(
-      `local.${vatID}.lastSnapshot`,
-      JSON.stringify({ snapshotID, startPos: endPosition }),
-    );
-    addToSnapshot(snapshotID);
     kernelSlog.write({
       type: 'heap-snapshot-save',
       vatID,
-      snapshotID,
+      hash,
       rawByteCount,
       rawSaveSeconds,
       compressedByteCount,
@@ -630,17 +559,15 @@ export function makeVatKeeper(
     return true;
   }
 
+  function deleteSnapshots() {
+    if (snapStore) {
+      snapStore.deleteVatSnapshots(vatID);
+    }
+  }
+
   function removeSnapshotAndTranscript() {
-    const skey = `local.${vatID}.lastSnapshot`;
     if (snapStore) {
-      const notation = kvStore.get(skey);
-      if (notation) {
-        const { snapshotID } = JSON.parse(notation);
-        if (removeFromSnapshot(snapshotID) === 0) {
-          snapStore.deleteSnapshot(snapshotID);
-        }
-        kvStore.delete(skey);
-      }
+      snapStore.deleteVatSnapshots(vatID);
     }
 
     const endPos = getRequired(`${vatID}.t.endPosition`);
@@ -719,8 +646,8 @@ export function makeVatKeeper(
     vatStats,
     dumpState,
     saveSnapshot,
-    getLastSnapshot,
-    removeFromSnapshot,
+    deleteSnapshots,
+    getSnapshotInfo,
     removeSnapshotAndTranscript,
   });
 }

packages/SwingSet/src/kernel/vat-loader/manager-helper.js

@@ -47,7 +47,7 @@ import { makeTranscriptManager } from './transcript.js';
 /**
  *
  * @typedef { { getManager: (shutdown: () => Promise<void>,
- *                           makeSnapshot?: (ss: SnapStore) => Promise<SnapshotInfo>) => VatManager,
+ *                           makeSnapshot?: (endPos: number, ss: SnapStore) => Promise<SnapshotResult>) => VatManager,
  *              syscallFromWorker: (vso: VatSyscallObject) => VatSyscallResult,
  *              setDeliverToWorker: (dtw: unknown) => void,
  *            } } ManagerKit
@@ -259,7 +259,7 @@ function makeManagerKit(
   /**
    *
    * @param { () => Promise<void>} shutdown
-   * @param {(ss: SnapStore) => Promise<SnapshotInfo>} makeSnapshot
+   * @param {(endPos: number, ss: SnapStore) => Promise<SnapshotResult>} makeSnapshot
    * @returns {VatManager}
    */
   function getManager(shutdown, makeSnapshot) {

packages/SwingSet/src/kernel/vat-loader/manager-subprocess-xsnap.js

@@ -22,7 +22,7 @@ const decoder = new TextDecoder();
  *   allVatPowers: VatPowers,
  *   kernelKeeper: KernelKeeper,
  *   kernelSlog: KernelSlog,
- *   startXSnap: (name: string, handleCommand: AsyncHandler, metered?: boolean, snapshotHash?: string) => Promise<XSnap>,
+ *   startXSnap: (vatID: string, name: string, handleCommand: AsyncHandler, metered?: boolean, reload?: boolean) => Promise<XSnap>,
  *   testLog: (...args: unknown[]) => void,
  * }} tools
  * @returns {VatManagerFactory}
@@ -112,10 +112,9 @@ export function makeXsSubprocessFactory({
     }
 
     const vatKeeper = kernelKeeper.provideVatKeeper(vatID);
-    const lastSnapshot = vatKeeper.getLastSnapshot();
-    if (lastSnapshot) {
-      const { snapshotID } = lastSnapshot;
-      kernelSlog.write({ type: 'heap-snapshot-load', vatID, snapshotID });
+    const snapshotInfo = vatKeeper.getSnapshotInfo();
+    if (snapshotInfo) {
+      kernelSlog.write({ type: 'heap-snapshot-load', vatID, ...snapshotInfo });
     }
 
     // `startXSnap` adds `argName` as a dummy argument so that 'ps'
@@ -125,10 +124,11 @@ export function makeXsSubprocessFactory({
 
     // start the worker and establish a connection
     const worker = await startXSnap(
+      vatID,
       argName,
       handleCommand,
       metered,
-      lastSnapshot ? lastSnapshot.snapshotID : undefined,
+      !!snapshotInfo,
     );
 
     /** @type { (item: Tagged) => Promise<CrankResults> } */
@@ -144,7 +144,7 @@ export function makeXsSubprocessFactory({
       return { ...result, reply: [tag, ...rest] };
     }
 
-    if (lastSnapshot) {
+    if (snapshotInfo) {
       parentLog(vatID, `snapshot loaded. dispatch ready.`);
     } else {
       parentLog(vatID, `instructing worker to load bundle..`);
@@ -209,11 +209,12 @@ export function makeXsSubprocessFactory({
       return worker.close().then(_ => undefined);
     }
     /**
+     * @param {number} endPos
      * @param {SnapStore} snapStore
-     * @returns {Promise<SnapshotInfo>}
+     * @returns {Promise<SnapshotResult>}
      */
-    function makeSnapshot(snapStore) {
-      return snapStore.save(fn => worker.snapshot(fn));
+    function makeSnapshot(endPos, snapStore) {
+      return snapStore.saveSnapshot(vatID, endPos, fn => worker.snapshot(fn));
     }
 
     return mk.getManager(shutdown, makeSnapshot);

packages/SwingSet/src/kernel/vat-warehouse.js

@@ -125,9 +125,9 @@ export function makeVatWarehouse(kernelKeeper, vatLoader, policyOptions) {
     // TODO(3218): persist this option; avoid spinning up a vat that isn't pipelined
     const { enablePipelining = false } = options;
 
-    const lastSnapshot = vatKeeper.getLastSnapshot();
+    const snapshotInfo = vatKeeper.getSnapshotInfo();
     await manager.replayTranscript(
-      lastSnapshot ? lastSnapshot.startPos : undefined,
+      snapshotInfo ? snapshotInfo.endPos : undefined,
     );
 
     const result = {

packages/SwingSet/src/types-ambient.js

@@ -118,7 +118,7 @@
  * @typedef { import('./types-external.js').VatManagerFactory } VatManagerFactory
  * @typedef { import('./types-external.js').VatManager } VatManager
  * @typedef { import('./types-external.js').SnapStore } SnapStore
- * @typedef { import('./types-external.js').SnapshotInfo } SnapshotInfo
+ * @typedef { import('./types-external.js').SnapshotResult } SnapshotResult
  * @typedef { import('./types-external.js').WaitUntilQuiescent } WaitUntilQuiescent
  */
 

packages/SwingSet/src/types-external.js

@@ -221,7 +221,7 @@ export {};
  *            } } VatManagerFactory
  * @typedef { { deliver: (delivery: VatDeliveryObject) => Promise<VatDeliveryResult>,
  *              replayTranscript: (startPos: StreamPosition | undefined) => Promise<number?>,
- *              makeSnapshot?: (ss: SnapStore) => Promise<SnapshotInfo>,
+ *              makeSnapshot?: (endPos: number, ss: SnapStore) => Promise<SnapshotResult>,
  *              shutdown: () => Promise<void>,
  *            } } VatManager
  *
@@ -291,7 +291,7 @@ export {};
 /**
  * @typedef { import('@agoric/swing-store').KVStore } KVStore
  * @typedef { import('@agoric/swing-store').SnapStore } SnapStore
- * @typedef { import('@agoric/swing-store').SnapshotInfo } SnapshotInfo
+ * @typedef { import('@agoric/swing-store').SnapshotResult } SnapshotResult
  * @typedef { import('@agoric/swing-store').StreamStore } StreamStore
  * @typedef { import('@agoric/swing-store').StreamPosition } StreamPosition
  * @typedef { import('@agoric/swing-store').SwingStore } SwingStore

packages/SwingSet/test/test-state.js

@@ -697,11 +697,7 @@ test('crankhash - skip keys', t => {
   // certain local keys are excluded from consensus, and should not affect
   // the hash
   k.kvStore.set('one', '1');
-  k.kvStore.set('local.snapshot.XYZ', '["vat1234"]');
-  k.kvStore.set(
-    'local.v1234.lastSnapshot',
-    '{"snapshotID":"XYZ","startPos":4}',
-  );
+  k.kvStore.set('local.doNotHashMe', 'random nonsense');
   t.throws(() => k.kvStore.set('host.foo', 'bar'));
   t.is(k.emitCrankHashes().crankhash, expCrankhash);
 });

packages/SwingSet/test/test-xsnap-errors.js

@@ -38,7 +38,7 @@ test('child termination distinguished from meter exhaustion', async t => {
   /** @type { any } */
   const kernelKeeper = {
     provideVatKeeper: () => ({
-      getLastSnapshot: () => undefined,
+      getSnapshotInfo: () => undefined,
       addToTranscript: () => undefined,
     }),
     getRelaxDurabilityRules: () => false,
@@ -60,6 +60,7 @@ test('child termination distinguished from meter exhaustion', async t => {
   // @ts-expect-error close enough for this test
   const managerOptions = { useTranscript: true };
   const schandler = _vso => ['ok', null];
+
   const m = await xsWorkerFactory.createFromBundle(
     'v1',
     bundle,