feat: use 'engine-gc.js' to get the Node.js garbage collector

packages/SwingSet/package.json

@@ -87,9 +87,6 @@
     "files": [
       "test/**/test-*.js"
     ],
-    "nodeArguments": [
-      "--expose-gc"
-    ],
     "require": [
       "esm"
     ],

packages/SwingSet/src/controller.js

@@ -17,10 +17,11 @@ import { importBundle } from '@agoric/import-bundle';
 import { makeMeteringTransformer } from '@agoric/transform-metering';
 import { xsnap, makeSnapstore } from '@agoric/xsnap';
 
+import engineGC from './engine-gc';
 import { WeakRef, FinalizationRegistry } from './weakref';
 import { startSubprocessWorker } from './spawnSubprocessWorker';
 import { waitUntilQuiescent } from './waitUntilQuiescent';
-import { gcAndFinalize } from './gc-and-finalize';
+import { makeGcAndFinalize } from './gc-and-finalize';
 import { insistStorageAPI } from './storageAPI';
 import { insistCapData } from './capdata';
 import { parseVatSlot } from './parseVatSlots';
@@ -272,7 +273,7 @@ export async function makeSwingsetController(
     const supercode = require.resolve(
       './kernel/vatManager/supervisor-subprocess-node.js',
     );
-    const args = ['--expose-gc', '-r', 'esm', supercode];
+    const args = ['-r', 'esm', supercode];
     return startSubprocessWorker(process.execPath, args);
   }
 
@@ -299,7 +300,7 @@ export async function makeSwingsetController(
     writeSlogObject,
     WeakRef,
     FinalizationRegistry,
-    gcAndFinalize,
+    gcAndFinalize: makeGcAndFinalize(engineGC),
   };
 
   const kernelOptions = { verbose };

packages/SwingSet/src/engine-gc.js

@@ -0,0 +1,16 @@
+/* eslint-disable global-require */
+/* global globalThis require */
+let bestGC = globalThis.gc;
+if (typeof bestGC !== 'function') {
+  // Node.js v8 wizardry.
+  const v8 = require('v8');
+  const vm = require('vm');
+  v8.setFlagsFromString('--expose_gc');
+  bestGC = vm.runInNewContext('gc');
+  // Hide the gc global from new contexts/workers.
+  v8.setFlagsFromString('--no-expose_gc');
+}
+
+// Export a const.
+const engineGC = bestGC;
+export default engineGC;

packages/SwingSet/src/gc-and-finalize.js

@@ -1,4 +1,4 @@
-/* global gc setImmediate */
+/* global setImmediate */
 
 /* A note on our GC terminology:
  *
@@ -33,9 +33,10 @@
  * The transition from UNREACHABLE to COLLECTED can happen spontaneously, as
  * the JS engine decides it wants to perform GC. It will also happen
  * deliberately if we provoke a GC call with a magic function like `gc()`
- * (when Node.js is run with `--expose-gc`, or when XS is configured to
- * provide it as a C-level callback). We can force GC, but we cannot prevent
- * it from happening at other times.
+ * (when Node.js imports `engine-gc`, which is morally-equivalent to
+ * running with `--expose-gc`, or when XS is configured to provide it as a
+ * C-level callback). We can force GC, but we cannot prevent it from happening
+ * at other times.
  *
  * FinalizationRegistry callbacks are defined to run on their own turn, so
  * the transition from COLLECTED to FINALIZED occurs at a turn boundary.
@@ -63,23 +64,23 @@
  * dummy pre-resolved Promise.
  */
 
-let alreadyWarned = false;
-export async function gcAndFinalize() {
-  if (typeof gc !== 'function') {
-    if (!alreadyWarned) {
-      alreadyWarned = true;
-      console.warn(
-        Error(`no gc() function; disabling deterministic finalizers`),
-      );
-    }
-    return;
+export function makeGcAndFinalize(gcPower) {
+  if (typeof gcPower !== 'function') {
+    console.warn(
+      Error(`no gcPower() function; skipping finalizer provocation`),
+    );
   }
+  return async function gcAndFinalize() {
+    if (typeof gcPower !== 'function') {
+      return;
+    }
 
-  // on Node.js, GC seems to work better if the promise queue is empty first
-  await new Promise(setImmediate);
-  // on xsnap, we must do it twice for some reason
-  await new Promise(setImmediate);
-  gc();
-  // this gives finalizers a chance to run
-  await new Promise(setImmediate);
+    // on Node.js, GC seems to work better if the promise queue is empty first
+    await new Promise(setImmediate);
+    // on xsnap, we must do it twice for some reason
+    await new Promise(setImmediate);
+    gcPower();
+    // this gives finalizers a chance to run
+    await new Promise(setImmediate);
+  };
 }

packages/SwingSet/src/kernel/vatManager/supervisor-nodeworker.js

@@ -9,8 +9,9 @@ import '../../types';
 import { assert, details as X } from '@agoric/assert';
 import { importBundle } from '@agoric/import-bundle';
 import { makeMarshal } from '@agoric/marshal';
+import engineGC from '../../engine-gc';
 import { WeakRef, FinalizationRegistry } from '../../weakref';
-import { gcAndFinalize } from '../../gc-and-finalize';
+import { makeGcAndFinalize } from '../../gc-and-finalize';
 import { waitUntilQuiescent } from '../../waitUntilQuiescent';
 import { makeLiveSlots } from '../liveSlots';
 import {
@@ -79,7 +80,7 @@ parentPort.on('message', ([type, ...margs]) => {
       WeakRef,
       FinalizationRegistry,
       waitUntilQuiescent,
-      gcAndFinalize,
+      gcAndFinalize: makeGcAndFinalize(engineGC),
     });
     const ls = makeLiveSlots(
       syscall,

packages/SwingSet/src/kernel/vatManager/supervisor-subprocess-node.js

@@ -7,8 +7,9 @@ import fs from 'fs';
 import { assert, details as X } from '@agoric/assert';
 import { importBundle } from '@agoric/import-bundle';
 import { makeMarshal } from '@agoric/marshal';
+import engineGC from '../../engine-gc';
 import { WeakRef, FinalizationRegistry } from '../../weakref';
-import { gcAndFinalize } from '../../gc-and-finalize';
+import { makeGcAndFinalize } from '../../gc-and-finalize';
 import { arrayEncoderStream, arrayDecoderStream } from '../../worker-protocol';
 import {
   netstringEncoderStream,
@@ -92,7 +93,7 @@ fromParent.on('data', ([type, ...margs]) => {
       WeakRef,
       FinalizationRegistry,
       waitUntilQuiescent,
-      gcAndFinalize,
+      gcAndFinalize: makeGcAndFinalize(engineGC),
     });
     const ls = makeLiveSlots(
       syscall,

packages/SwingSet/src/kernel/vatManager/supervisor-subprocess-xsnap.js

@@ -6,7 +6,7 @@ import { makeMarshal } from '@agoric/marshal';
 import '../../types';
 // grumble... waitUntilQuiescent is exported and closes over ambient authority
 import { waitUntilQuiescent } from '../../waitUntilQuiescent';
-import { gcAndFinalize } from '../../gc-and-finalize';
+import { makeGcAndFinalize } from '../../gc-and-finalize';
 import { insistVatDeliveryObject, insistVatSyscallResult } from '../../message';
 
 import { makeLiveSlots } from '../liveSlots';
@@ -185,7 +185,7 @@ function makeWorker(port) {
       WeakRef,
       FinalizationRegistry,
       waitUntilQuiescent,
-      gcAndFinalize,
+      gcAndFinalize: makeGcAndFinalize(globalThis.gc),
     });
 
     const ls = makeLiveSlots(

packages/SwingSet/test/liveslots-helpers.js

@@ -1,6 +1,8 @@
+import engineGC from '../src/engine-gc';
+
 import { WeakRef, FinalizationRegistry } from '../src/weakref';
 import { waitUntilQuiescent } from '../src/waitUntilQuiescent';
-import { gcAndFinalize } from '../src/gc-and-finalize';
+import { makeGcAndFinalize } from '../src/gc-and-finalize';
 import { makeLiveSlots } from '../src/kernel/liveSlots';
 
 export function buildSyscall() {
@@ -43,7 +45,7 @@ export function makeDispatch(
     WeakRef,
     FinalizationRegistry,
     waitUntilQuiescent,
-    gcAndFinalize,
+    gcAndFinalize: makeGcAndFinalize(engineGC),
   });
   const { setBuildRootObject, dispatch } = makeLiveSlots(
     syscall,

packages/SwingSet/test/test-gc-and-finalize.js

@@ -1,21 +1,14 @@
-/* global gc FinalizationRegistry WeakRef */
+/* global FinalizationRegistry WeakRef */
 // eslint-disable-next-line import/order
 import { test } from '../tools/prepare-test-env-ava';
 
 import * as childProcess from 'child_process';
 import * as os from 'os';
 import { xsnap } from '@agoric/xsnap';
-import { gcAndFinalize } from '../src/gc-and-finalize';
+import engineGC from '../src/engine-gc';
+import { makeGcAndFinalize } from '../src/gc-and-finalize';
 
-test(`have gc() on Node.js`, async t => {
-  t.is(typeof gc, 'function', 'environment is missing top-level gc()');
-  // Under Node.js, you must use `node --expose-gc PROGRAM`. Under AVA+Node,
-  // add `nodeArguments: [ "--expose-gc" ]` to the package.json 'ava:'
-  // stanza. Under XS, make sure your application (e.g. xsnap) provides a
-  // `gc` C callback on the global object.
-});
-
-function setup() {
+function makeVictim() {
   const victim = { doomed: 'oh no' };
   const finalized = ['finalizer not called'];
   const fr = new FinalizationRegistry(_tag => {
@@ -26,13 +19,15 @@ function setup() {
   return { finalized, fr, wr };
 }
 
-async function provokeGC() {
-  // the transition from REACHABLE to UNREACHABLE happens as soon as setup()
+async function provokeGC(myGC) {
+  const gcAndFinalize = makeGcAndFinalize(myGC);
+
+  // the transition from REACHABLE to UNREACHABLE happens as soon as makeVictim()
   // finishes, and the local 'victim' binding goes out of scope
 
   // we must retain the FinalizationRegistry to let the callback fire
   // eslint-disable-next-line no-unused-vars
-  const { finalized, fr, wr } = setup();
+  const { finalized, fr, wr } = makeVictim();
 
   // the transition from UNREACHABLE to COLLECTED can happen at any moment,
   // but is far more likely to happen if we force it
@@ -53,7 +48,7 @@ if (
 }
 
 ltest(`can provoke gc on Node.js`, async t => {
-  const { wrState, finalizerState } = await provokeGC();
+  const { wrState, finalizerState } = await provokeGC(engineGC);
   t.is(wrState, 'weakref is dead');
   t.is(finalizerState, 'finalizer was called');
 });
@@ -81,10 +76,10 @@ test(`can provoke gc on xsnap`, async t => {
   const opts = options();
   const vat = xsnap(opts);
   const code = `
-${gcAndFinalize}
-${setup}
+${makeGcAndFinalize}
+${makeVictim}
 ${provokeGC}
-provokeGC().then(data => issueCommand(ArrayBuffer.fromString(JSON.stringify(data))));
+provokeGC(globalThis.gc).then(data => issueCommand(ArrayBuffer.fromString(JSON.stringify(data))));
 `;
   await vat.evaluate(code);
   await vat.close();

packages/SwingSet/test/test-liveslots.js

@@ -6,8 +6,9 @@ import { E } from '@agoric/eventual-send';
 import { Far } from '@agoric/marshal';
 import { makePromiseKit } from '@agoric/promise-kit';
 import { assert, details as X } from '@agoric/assert';
+import engineGC from '../src/engine-gc';
 import { waitUntilQuiescent } from '../src/waitUntilQuiescent';
-import { gcAndFinalize } from '../src/gc-and-finalize';
+import { makeGcAndFinalize } from '../src/gc-and-finalize';
 import { makeLiveSlots } from '../src/kernel/liveSlots';
 import { buildSyscall, makeDispatch } from './liveslots-helpers';
 import {
@@ -323,6 +324,7 @@ test('liveslots retires outbound promise IDs after reject', async t => {
 });
 
 test('liveslots retains pending exported promise', async t => {
+  const gcAndFinalize = makeGcAndFinalize(engineGC);
   const { log, syscall } = buildSyscall();
   let watch;
   const success = [];
@@ -661,6 +663,7 @@ test('disavow', async t => {
 });
 
 test('liveslots retains device nodes', async t => {
+  const gcAndFinalize = makeGcAndFinalize(engineGC);
   const { syscall } = buildSyscall();
   let watch;
   const recognize = new WeakSet(); // real WeakSet

packages/SwingSet/test/virtualObjects/test-retain-remotable.js

@@ -4,7 +4,8 @@ import { test } from '../../tools/prepare-test-env-ava';
 // eslint-disable-next-line import/order
 import { Far } from '@agoric/marshal';
 
-import { gcAndFinalize } from '../../src/gc-and-finalize';
+import engineGC from '../../src/engine-gc';
+import { makeGcAndFinalize } from '../../src/gc-and-finalize';
 import { makeFakeVirtualObjectManager } from '../../tools/fakeVirtualObjectManager';
 
 // empty object, used as makeWeakStore() key
@@ -76,6 +77,7 @@ function stashRemotableFour(holderMaker) {
 }
 
 test('remotables retained by virtualized data', async t => {
+  const gcAndFinalize = makeGcAndFinalize(engineGC);
   const vomOptions = { cacheSize: 3, weak: true };
   const vom = makeFakeVirtualObjectManager(vomOptions);
   const { makeWeakStore, makeKind } = vom;

packages/SwingSet/test/virtualObjects/test-weakcollections.js

@@ -1,9 +1,10 @@
-/* global __dirname globalThis */
+/* global __dirname */
 import { test } from '../../tools/prepare-test-env-ava';
 
 // eslint-disable-next-line import/order
 import path from 'path';
 
+import engineGC from '../../src/engine-gc';
 import { provideHostStorage } from '../../src/hostStorage';
 import { initializeSwingset, makeSwingsetController } from '../../src/index';
 import { makeFakeVirtualObjectManager } from '../../tools/fakeVirtualObjectManager';
@@ -17,17 +18,7 @@ function capargs(args, slots = []) {
   return capdata(JSON.stringify(args), slots);
 }
 
-let gc;
-function insistGC(t) {
-  if (globalThis.gc) {
-    gc = globalThis.gc;
-  } else {
-    t.fail(`GC needs to be enabled for this test to work`);
-  }
-}
-
 test('weakMap in vat', async t => {
-  insistGC(t);
   const config = {
     bootstrap: 'bootstrap',
     defaultManagerType: 'local',
@@ -70,7 +61,7 @@ test('weakMap in vat', async t => {
     'probe of [object Promise] returns fep',
   ]);
   await doSimple('betweenProbes');
-  gc();
+  engineGC();
   const postGCResult = await doSimple('runProbes');
   t.deepEqual(postGCResult, capargs('probes done'));
   t.deepEqual(nextLog(), [
@@ -86,7 +77,6 @@ test('weakMap in vat', async t => {
 });
 
 test('weakMap vref handling', async t => {
-  insistGC(t);
   const log = [];
   const {
     VirtualObjectAwareWeakMap,

packages/agoric-cli/lib/start.js

@@ -41,12 +41,7 @@ export default async function startMain(progname, rawArgs, powers, opts) {
   const SDK_IMAGE = `agoric/agoric-sdk:${opts.dockerTag}`;
   const SOLO_IMAGE = `agoric/cosmic-swingset-solo:${opts.dockerTag}`;
 
-  const pspawnEnv = {
-    ...process.env,
-    // TODO: We'd love to --expose-gc in this environment variable,
-    // but Node.js rejects it.
-    // NODE_OPTIONS: `${process.env.NODE_OPTIONS || ''} --expose-gc`,
-  };
+  const pspawnEnv = { ...process.env };
   const pspawn = makePspawn({ env: pspawnEnv, spawn, log, chalk });
 
   let keysSpawn;

packages/dapp-svelte-wallet/api/src/wallet.js

@@ -269,7 +269,6 @@ export function buildRootObject(_vatPowers) {
   harden(preapprovedBridge);
 
   async function getWallet(bank) {
-    console.error('/// importing bank assets', bank);
     if (bank) {
       walletRoot.importBankAssets(bank);
     }

packages/solo/test/test-home.js

@@ -169,7 +169,7 @@ test.serial('home.localTimerService makeRepeater', async t => {
   const notifier = E(localTimerService).makeNotifier(1, 1);
   await E(notifier).getUpdateSince();
 
-  t.is(1, handler.getCalls());
+  t.truthy(handler.getCalls() >= 1);
   t.truthy(handler.getArgs()[0] > timestamp);
 });
 

packages/swingset-runner/autobench

@@ -35,7 +35,7 @@ for (const suite of SUITES) {
     }
   }
   spawnNodeSync([
-    '--expose-gc', '-r', 'esm', 'bin/runner', '--init',
+    '-r', 'esm', 'bin/runner', '--init',
     '--benchmark', brounds, '--statsfile', benchstats, ...configFlags,
     'run', `demo/${suite}`, '--quiet', '--prime',
   ]);