node-api: generalize finalizer second pass callback #44141

legendecas · 2022-08-05T07:09:07Z

Generalize the finalizer's second pass callback to make it cancellable and simplify the code around the second pass callback.

With this change, it is determined that Reference::Finalize/RefBase::Finalize are called once, either from the env's shutdown, or from the env's second pass callback.

All existing node-api js tests should pass without a touch. The js_native_api cctest is no longer applicable with this change, just removing it.

Refs: #44071

nodejs-github-bot · 2022-08-05T07:09:11Z

Review requested:

@nodejs/gyp
@nodejs/node-api

nodejs-github-bot · 2022-08-07T06:23:14Z

CI: https://ci.nodejs.org/job/node-test-pull-request/45890/

test.parallel/test-diagnostics-channel-net

nodejs-github-bot · 2022-08-09T03:09:43Z

CI: https://ci.nodejs.org/job/node-test-pull-request/45940/

Jenkins failure: https://ci.nodejs.org/job/node-test-commit-freebsd/45349/nodes=freebsd12-x64/

nodejs-github-bot · 2022-08-09T16:57:10Z

CI: https://ci.nodejs.org/job/node-test-pull-request/45952/

vmoroz · 2022-08-18T22:08:49Z

src/node_api.cc

+  if (!finalization_scheduled) {
+    finalization_scheduled = true;
+    Ref();
+    node_env()->SetImmediate([this](node::Environment* node_env) {


Capturing this is not safe: if the lambda is not executed, then the env instance is never released. It would be better to use the EnvRefHolder here which is being deleted in this PR from js_native_api_v8.h. This way the Unref() is always called when the lambda is released.
Also, when we call the Unref() below we must be prepared that it was the last Unref() that causes the env instance destruction. In such case the DrainFinalizerQueue() may be called against deleted object and cause issues.

The callback of Environment::SetImmediate is deemed to be called. So we don't need additional setups for the condition that the callback is not invoked.

vmoroz · 2022-08-18T22:29:23Z

src/node_api.cc

+  while (!pending_finalizers.empty()) {
+    v8impl::RefTracker* ref_tracker = *pending_finalizers.begin();
+    pending_finalizers.erase(ref_tracker);
+    ref_tracker->Finalize();


How do we handle uncaught JS exceptions? Previously the SetImmediate code was taking care about the exceptions. It may be worth adding a test where we have a few finalizers running and they all throw JS exceptions. The JS code should handle and ignore those exceptions - we must see all the finalizers executed.
Also, we need to test that if JS does not handle the uncaught exceptions, then we crash as usual.

node_napi_env__::CallFinalizer still handles JS exception. Native SetImmediate doesn't handle JS exceptions.

src/node_api.cc

legendecas · 2022-10-14T07:14:15Z

@mhdawson thank you for verifying the patch with node-addon-api test sets.

I believe the problem here is what napi_remove_wrap should do when the out-param napi_ref result is set on napi_wrap. The document said that:

napi_remove_wrap:
Retrieves a native instance that was previously wrapped in the JavaScript object js_object using napi_wrap() and removes the wrapping. If a finalizer callback was associated with the wrapping, it will no longer be called when the JavaScript object becomes garbage-collected.
https://nodejs.org/api/n-api.html#napi_remove_wrap

However, I found that on the main branch, when the napi_remove_wrap is called but the napi_delete_reference is not called with the out-param napi_ref result, the finalizer can still be invoked. I've added a test case for it: https://github.com/nodejs/node/pull/44141/files#diff-8037a0113a35b91ac2d997501123d0b8be5b341907e9e350fe4f70082afa361f.

So basically, when the napi_wrap is called with non-null out-paramnapi_ref result, the expected behavior would be:

invoke napi_remove_wrap with the wrapped object to invalidate the wrap, after this point no finalizer should be invoked, and napi_get_reference_value can still get the ref-ed value from the out-param napi_ref result.
invoke napi_delete_reference with the out-param napi_ref result, to delete the user-owned napi_ref.

Generalize the finalizer's second pass callback to make it cancellable and simplify the code around the second pass callback. With this change, it is determined that Reference::Finalize or RefBase::Finalize are called once, either from the env's shutdown, or from the env's second pass callback. All existing node-api js tests should pass without a touch. The js_native_api cctest is no longer applicable with this change, just removing it.

nodejs-github-bot · 2022-11-18T16:46:30Z

CI: https://ci.nodejs.org/job/node-test-pull-request/48011/

legendecas · 2022-11-21T09:21:13Z

@mhdawson updated, PTAL again, thank you :)

src/node_api.cc

mhdawson

LGTM, I ran the node-addon-api tests 10000 times with these changes and they all passed.

Generalize the finalizer's second pass callback to make it cancellable and simplify the code around the second pass callback. With this change, it is determined that Reference::Finalize or RefBase::Finalize are called once, either from the env's shutdown, or from the env's second pass callback. All existing node-api js tests should pass without a touch. The js_native_api cctest is no longer applicable with this change, just removing it. PR-URL: #44141 Refs: #44071 Reviewed-By: Michael Dawson <[email protected]>

legendecas · 2022-12-19T17:45:13Z

Landed in f14fa1b

Generalize the finalizer's second pass callback to make it cancellable and simplify the code around the second pass callback. With this change, it is determined that Reference::Finalize or RefBase::Finalize are called once, either from the env's shutdown, or from the env's second pass callback. All existing node-api js tests should pass without a touch. The js_native_api cctest is no longer applicable with this change, just removing it. PR-URL: #44141 Refs: #44071 Reviewed-By: Michael Dawson <[email protected]>

Functions declared in anonymous namespaces are not necessarily to be marked as static. PR-URL: nodejs/node#44301 Refs: nodejs/node#44141 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Michael Dawson <[email protected]>

Generalize the finalizer's second pass callback to make it cancellable and simplify the code around the second pass callback. With this change, it is determined that Reference::Finalize or RefBase::Finalize are called once, either from the env's shutdown, or from the env's second pass callback. All existing node-api js tests should pass without a touch. The js_native_api cctest is no longer applicable with this change, just removing it. PR-URL: #44141 Refs: #44071 Reviewed-By: Michael Dawson <[email protected]>

See nodejs#44141

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CI Reliability 2022-08-08 nodejs/reliability#340

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CI Reliability 2022-08-09 nodejs/reliability#341

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node-api: fix immediate napi_remove_wrap test #45406

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legendecas and others added 2 commits November 18, 2022 09:33

fixup! verify dangling napi_ref in napi_wrap

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refactor: generalize finalizer second pass callback (nodejs/node#44141)

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v19.4.0 proposal #46061

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V18.14.0 proposal #46396

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Xmader added a commit to Distributive-Network/node that referenced this pull request May 14, 2025

Reference::Finalize/RefBase::Finalize was generalized

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See nodejs#44141

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