fix(swingset): rename snapshot-related DB keys to be "local"

We're defining the `local.*` namespace as the portion of the DB that is
excluded from consensus (the #3442 kernel activity hash). Vat snapshots are a
local concern: each member of a consensus machine can decide for itself
if/when to make a snapshot. So both the vat->snapshot and the snapshot->vats
tables must be moved to `local.`.

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

@@ -31,6 +31,10 @@ const enableKernelGC = true;
 // "prefix." and "prefix/", which avoids including anything using an
 // extension of the prefix (e.g. [vat1.foo, vat1.bar, vat15.baz]).
 //
+// The 'local.' namespace is excluded from the kernel activity hash, and is
+// allowed to vary between instances in a consensus machine. Everything else
+// is required to be deterministic.
+//
 // The schema is:
 //
 // vat.names = JSON([names..])
@@ -59,13 +63,13 @@ const enableKernelGC = true;
 // v$NN.vs.$key = string
 // v$NN.meter = m$NN
 // exclude from consensus
-// v$NN.lastSnapshot = JSON({ snapshotID, startPos })
+// local.v$NN.lastSnapshot = JSON({ snapshotID, startPos })
 
 // m$NN.remaining = $NN // remaining capacity (in computrons) or 'unlimited'
 // m$NN.threshold = $NN // notify when .remaining first drops below this
 
 // exclude from consensus
-// snapshot.$id = [vatID, ...]
+// local.snapshot.$id = [vatID, ...]
 
 // d$NN.o.nextID = $NN
 // d$NN.c.$kernelSlot = $deviceSlot = o-$NN/d+$NN/d-$NN

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

@@ -445,7 +445,7 @@ export function makeVatKeeper(
    * @returns {{ snapshotID: string, startPos: StreamPosition } | undefined}
    */
   function getLastSnapshot() {
-    const notation = kvStore.get(`${vatID}.lastSnapshot`);
+    const notation = kvStore.get(`local.${vatID}.lastSnapshot`);
     if (!notation) {
       return undefined;
     }
@@ -470,7 +470,7 @@ export function makeVatKeeper(
    * @param {string} snapshotID
    */
   function addToSnapshot(snapshotID) {
-    const key = `snapshot.${snapshotID}`;
+    const key = `local.snapshot.${snapshotID}`;
     const consumers = JSON.parse(kvStore.get(key) || '[]');
     assert(Array.isArray(consumers));
 
@@ -493,7 +493,7 @@ export function makeVatKeeper(
    * @param {string} snapshotID
    */
   function removeFromSnapshot(snapshotID) {
-    const key = `snapshot.${snapshotID}`;
+    const key = `local.snapshot.${snapshotID}`;
     const consumersJSON = kvStore.get(key);
     assert(consumersJSON, X`cannot remove ${vatID}: ${key} key not defined`);
     const consumers = JSON.parse(consumersJSON);
@@ -526,7 +526,7 @@ export function makeVatKeeper(
     }
     const endPosition = getTranscriptEndPosition();
     kvStore.set(
-      `${vatID}.lastSnapshot`,
+      `local.${vatID}.lastSnapshot`,
       JSON.stringify({ snapshotID, startPos: endPosition }),
     );
     addToSnapshot(snapshotID);

packages/SwingSet/test/vat-warehouse/test-reload-snapshot.js

@@ -33,7 +33,7 @@ test('vat reload from snapshot', async t => {
   const vatID = c1.vatNameToID('target');
 
   function getPositions() {
-    const lastSnapshot = hostStorage.kvStore.get(`${vatID}.lastSnapshot`);
+    const lastSnapshot = hostStorage.kvStore.get(`local.${vatID}.lastSnapshot`);
     const start = lastSnapshot
       ? JSON.parse(lastSnapshot).startPos.itemCount
       : 0;

packages/SwingSet/test/vat-warehouse/test-warehouse.js

@@ -103,10 +103,10 @@ test('4 vats in warehouse with 2 online', async t => {
 
 function unusedSnapshotsOnDisk(kvStore, snapstorePath) {
   const inUse = [];
-  for (const k of kvStore.getKeys(`snapshot.`, `snapshot/`)) {
+  for (const k of kvStore.getKeys(`local.snapshot.`, `local.snapshot/`)) {
     const consumers = JSON.parse(kvStore.get(k));
     if (consumers.length > 0) {
-      const id = k.slice(`snapshot.`.length);
+      const id = k.slice(`local.snapshot.`.length);
       inUse.push(id);
     }
   }