Extend Node-API to `libnode` #43542

mmomtchev · 2022-06-22T22:54:08Z

This PR adds support for instantiation and further interaction with an embedded version of Node.js (libnode) entirely through Node-API.

Refs: #43516

nodejs-github-bot · 2022-06-22T22:54:12Z

Review requested:

@nodejs/gyp
@nodejs/node-api

addaleax · 2022-06-23T09:45:00Z

doc/api/n-api.md

@@ -515,6 +515,8 @@ the currently running Agent which was set by means of a previous call to
 `napi_set_instance_data()` will be overwritten. If a `finalize_cb` was provided
 by the previous call, it will not be called.

+Not compatible with `libnode`.


What would this mean?

That API call is not to be used when using libnode

Because you don't need it - in this case it is the C++ software that will create environments, so it doesn't need the ability to carry its own context in this structure - and because the instance_data pointer is used to carry the libnode context.

Yes, but that doesn’t mean that this call is not compatible with libnode or with embedded mode.

It does because, before these new methods, there was no way to use Node-API with libnode at all.

addaleax · 2022-06-23T09:45:05Z

doc/api/n-api.md

@@ -6267,6 +6269,95 @@ idempotent.

 This API may only be called from the main thread.

+## Using Node.js as a shared library (`libnode`)


This has nothing to do with shared library mode.

This API allows using libnode through Node-API and it has no other uses.

That’s … wrong? Embedding and usage as a shared library are conceptually related but technically orthogonal.

Ok, let's call it Using an embedded version of Node.js

addaleax · 2022-06-23T09:47:45Z

doc/api/embedding.md

+<!--introduced_in=REPLACEME-->
+
+As an alternative, an embedded Node.js can also be fully controlled through
+Node-API. This API supports both C and C++ through [node-addon-api][].


If we do this, we should probably start adding converters between some Node-API values and V8/Node.js C++ API values (napi_value ↔ Local<Value>, napi_env ↔ Environment*/Isolate*).

The reason nobody has implemented a Node-API embedder API yet is that as an embedder, you often need fine-grained control over a lot of V8 options, and it’s not very practical to mirror the entire V8/Node.js embedder API to C (and that the Node.js C++ embedder API itself still has some rough edges that should probably be ironed out first).

If you need to use raw V8 primitives then you can't use Node-API - this applies to both Node.js -> C++ (binary node addons) and to C++ -> Node.js (libnode). Still this API covers lots of use cases - mostly C++ software that needs to accept JS plugins. It does not cover Electron which has very particular needs.
Allowing for more fine-grained control over the initialisation is of course something that should be considered.

If you need to use raw V8 primitives then you can't use Node-API

Right, that’s why I’m bringing this up.

Should you be able to mix V8 primitives and Node-API is another topic. If you take the ABI compatibility out of Node-API, there remains little use for it. However node-addon-api is a truly higher level API and it is much more practical to use from C++ then raw V8. Maybe there is a use case for software which has 95% node-addon-api and 5% custom V8 code. But this is something that goes beyond this PR - and it probably can be used both by embedders and addon authors.

I believe Cloudflare (service) Workers will need converters. Is this a Private API thing?

addaleax

I would strongly encourage you to go through the current embedder API and understand how embedders use it. I would love to see a C embedding API, but since the goal of Node-API-style APIs is to provide long-term stability, it’s going to need to be an API that is designed to account for multiple usage patterns (e.g.: integration with libuv, usage with a node-addon-api-style C++ wrapper) and probably some kind of API versioning in advance (since Node.js and V8 embedding changes their API definitions much more frequently than JS changes as a language).

addaleax · 2022-06-24T09:39:47Z

src/js_native_api_v8.cc

+  {
+    int r = node::SpinEventLoop(node_env->node_env()).FromMaybe(1);
+    if (exit_code != nullptr) *exit_code = r;
+    node::Stop(node_env->node_env());
+  }


It’s going to be heavily counterintuitive that this is part of a destruction operation.

Once you have drained the event loop, you have no other course of action then to destroy the environment - this is the reason I did it this way. There is no point in having a separate API call, if you will always have to call both of them one after the other. The real question is can we (and should we) keep an environment when its event loops is empty? This would allow to call async functions in a persistent environment but it will introduce a significant difference between the stand-alone Node.js and a embedded Node.js.

You could want to take an action in response to the event loop being drained, though?

The real question is can we (and should we) keep an environment when its event loops is empty?

I think the answer to both questions here is yes.

Ok, but this would require splitting node::SpinEventLoop into iteration and cleanup and it is something that is not possible with the current embedders' API.

… but it is? The docs for SpinEventLoop say which steps it takes, and all of those are public API. SpinEventLoop() is a helper, not a building block, and exists only for convenience and stronger API stability for those for whom it is sufficient.

Ok, I added napi_run_environment that spins up the event loop without destroying the environment when it is emptied and a unit test with an async callback.

KevinEady · 2022-06-24T15:33:03Z

We discussed this PR in the 24 June 2022 Node API meeting. Our main concerns are:

As @addaleax mentioned, people who are embedding Node into their application may require specific, fine-grained startup and configuration of the engine. We fear that creating any Node-API wrapper around engine initialization would bypass the ability to modify the engine startup properties as necessary. Furthermore, if there were engine-specific configurations, these concepts may not extend to other engines.
This PR creates V8-specific objects like the platform. Other engines, eg. Hermes, does not have these concepts and it may be incorrect to label these types as such. Additions to Node-API must be platform-agnostic. We have some baseline requirements in Contributing a new API to Node-API.

As of now, Node does not provide any APIs that are "Node-engine specific", because our Node-API is meant to be engine-agnostic. The existing Node-specific APIs, eg. node::InitializeNodeWithArgs are available within the C++ language but not in an ABI-stable C language. It may be beneficial to create some APIs that are outside of the Node-API scope, but are still C-based and provide ABI stability in order to perform this embedding scenario, where we can ignore the platform-agnostic requirement, ie. inside a different header file.

mmomtchev · 2022-06-24T15:42:54Z

@KevinEady

I agree that this API would not cover all use cases - in particular Electron has very specific requirements - but if you look at these exchanges, you will see that even their team was interested in some form of ABI or at least ABI stability. Still, such an API will be sufficient for a very significant portion of the uses cases. What needs discussing is:

How can greater customisability of the engine startup be supported and where should the line be drawn
Should we support mixed use with conversions between v8::Local and napi

I don't think that napi_platform is V8-specific - every engine would have a common main initialisation procedure and will support a single or many independent environments.

KevinEady · 2022-07-01T15:53:05Z

We discussed in the 1 July 2022 Node API meeting, and we did want to bring up again the comment we had before:

It may be beneficial to create some APIs that are outside of the Node-API scope, but are still C-based and provide ABI stability in order to perform this embedding scenario, where we can ignore the platform-agnostic requirement, ie. inside a different header file.

There is a logical separation between "module extensions API" and "node hosting API" so it may be beneficial to separate this embedding API into a separate header.

Regarding:

Should we support mixed use with conversions between v8::Local and napi

Can you clarify this a bit?

mmomtchev · 2022-07-01T18:14:31Z

Should we support mixed use with conversions between v8::Local and napi

Can you clarify this a bit?

Public API for retrieving the V8 reference from a napi* handle and a constructor for creating a napi* handle from a V8 reference. It goes against the Node-API logic, but it would allow extending Node-API without modifying it.

mmomtchev · 2022-07-05T14:59:31Z

@KevinEady @addaleax @rvagg My goal is to be able to support installation of this (libnode + this API) along a NodeSource Node.js package

Basically, I have two choices:

Either libnode & libnode-dev are completely independent of nodejs and install headers to /usr/include/libnode
Either I install this single new header file /usr/include/node - and then I require that nodejs is present and it is a specific version

Whatever I do at this point will likely stay. Do you have any opinion?

addaleax · 2022-07-05T15:02:55Z

@mmomtchev Two things:

I would not split header files from the existing header bundle, since the default for embedders will still be using the regular C++ APIs that are also used by addons
I would consider shipping the shared library variant of Node.js completely separate and independent from any embedding API additions or changes

mmomtchev · 2022-07-05T15:15:00Z

Ok, this is what I currently have - libnode93 and libnode108 which can be installed independently of nodejs - all three can be installed at the same time - and libnode-dev which is mutually exclusive with nodejs - because both install /usr/include/node

If/when this PR goes through, libnode-dev won't be necessary anymore

mmomtchev · 2022-07-05T17:01:35Z

@addaleax And do you have an idea for an elegant solution for having top-level functions appear in the global object the way they do in the REPL, besides vm.runInThisContext()? Ideally I would like to hide this from the end user.

addaleax · 2022-07-06T09:37:55Z

@mmomtchev If somebody wants that, they can just do the same thing the REPL does to make that happen, right?

mmomtchev · 2022-08-07T13:48:02Z

@addaleax I have a problem with restarting the event loop since NodePlatform::DrainTasks :

node/src/node_platform.cc

Line 440 in 3738b57

void NodePlatform::DrainTasks(Isolate* isolate) {

can be run only once per isolate. If I don't drain the tasks, some pending Promises (the dynamic import for example) do not get resolved. If I drain them, they do not get rescheduled. This is valid even when using the existing embedders' API. Do you have any opinion about it?

UPDATE: It is because node::PerIsolatePlatformData::FlushTasks is not called when using the embedders' API
UPDATE2: I found my problem (a resolved Promise does not keep the event loop from exiting) - but from having spent so much time in this part of the code, I think that all that FlushTasks/DrainTasks mess is completely useless. It is there for only one reason - because the flush_tasks_ async handle is unrefed to not prevent the event loop from exiting. This mechanism is called only a handful of times and if it was calling async_init / async_close every time, all those special edge cases wouldn't have been needed.

mhdawson · 2022-09-20T19:55:19Z

I was experimenting with using Node.js to support WASM containers. For that I needed to use libnode with crun. Unfortunately crun is current a C project and integrating the C++ API from libnode was going to be difficult (if crun would even consider moving to C++ versus C).

The model is to dlsym the required methods as crun support multiple engines and only wants to load the shared libraries needed.

With this PR is was relatively straight forward to get it working by using the new methods to start/get an env and then existing node-api methods to create and start a script to run.

At this for the simple run a script case it seemed to be enough. was experimenting with using Node.js to support WASM containers. For that I needed to use libnode with crun. Unfortunately crun is current a C project and integrating the C++ API from libnode was going to be difficult (if crun would even consider moving to C++ versus C).

The model is to dlsym the required methods as crun support multiple engines and only wants to load the shared libraries needed.

At this for the simple run a script case it seemed to be enough.

You can see what it used here: https://github.com/mhdawson/crun/blob/node-wasm-experiment/src/libcrun/handlers/wasmtime.c

vmoroz · 2022-10-11T18:19:54Z

src/js_native_api.h

@@ -102,6 +102,34 @@ node_api_symbol_for(napi_env env,
                    size_t length,
                    napi_value* result);
 #endif  // NAPI_EXPERIMENTAL
+
+#ifdef NAPI_EMBEDDING
+NAPI_EXTERN napi_status NAPI_CDECL napi_create_platform(int argc,


Currently the Node-API is split up between two files: js_native_api.h and node_api.h.
The difference is that the js_native_api.h contains only cross-engine JS-specific APIs and node_api.h has Node.JS-specific APIs.
We use js_native_api.h in different scenarios where we want to interact with different JS engine using ABI-safe Node-API functions. For example, see the Babylon Native, Hermes Node-API or V8-JSI. In all these scenarios we implement js_native_api.h APIs, and we do not use Node.JS or Node-specific node_api.h. Even the js_native_api_v8.h and js_native_api_v8.cc must be free from any Node.JS specific code. Any interaction with the Node-JS specific code must be done either through the functions declared in the js_native_api_v8_internals.h or overriding virtual napi_env__ in the derived node_napi_env__ class in the node_api_internals.h.
The node_api.h has the Node.js specific functions and mostly contains code concerning Node-JS modules and asynchronous code.
From this perspective, the Node.JS embedding API must not be part of the js_native_api.h header file. It could be in the node_api.h, but since this file is to be used by modules, the best option is to put these new APIs in their own node_hosting_api.h or node_embedding_api.h file. Other applications, such as Deno, could implement the full support for node_api.h and js_native_api.h to reuse the Node-API modules, but they would never implement the same Node.JS embedding APIs.
These embedding APIs are Node.JS specific and cannot be re-used for other engines or applications. E.g. other engines do not create a thread pool on their own, or cannot handle Node.JS CLI arguments.

@vmoroz I moved everything to a new header file, however I would just like to point out that if all those other engines do use N-API, then they would eventually support embedding, and this could become an universal API.
Currently options are passed as a C array of strings, which is an universal method - even if the options will probably be different - and the only one which is Node.js-centric is the thread_pool_size which probably should get transformed to something else before the API is set in stone.

samardzicneo · 2024-02-29T08:08:15Z

May one ask what the holdup is on this PR? Has OP lost interest? I'm part of a project that relies on this API and we're not too keen on using an unofficial fork and having to build Nodejs manually for all the platforms we support.

mhdawson · 2024-02-29T20:18:49Z

@samardzicneo do you have cycles to help get it across the line? I think @vmoroz also showed interest in moving this forward. @mmomtchev are you still going to have cycles or would it be good to have either @samardzicneo, @vmoroz or both try to move it forward?

samardzicneo · 2024-02-29T21:51:25Z

@samardzicneo do you have cycles to help get it across the line? I think @vmoroz also showed interest in moving this forward. @mmomtchev are you still going to have cycles or would it be good to have either @samardzicneo, @vmoroz or both try to move it forward?

Really, I'd love to do so, especially since I need this for a project of mine, but honestly, I don't trust my C/C++ skills enough to be sending PRs to Node 😅

Believe me, you don't want my messy code anywhere near your runtime.

vmoroz · 2024-03-08T15:18:38Z

@mmomtchev , I have moved the embedded code out of js_native_api_v8.cc to the new file node_api_embedding.cc. The main reason is that we support a scenario where the js_native_api_v8.cc can be used outside of Node.js code on its own.
(In node_api_embedding.cc line 81 is changed to have an explicit static_cast to suppress MSVC warning for int64_t to int32_t conversion).
Please review the change.

jasongin · 2024-03-08T20:13:56Z

src/node_api_embedding.cc

+  // and the v8::locker
+  delete emb_env;
+
+  cppgc::ShutdownProcess();


This call to ShutdownProcess() prevents another environment instance from being created in the same process. Specifically, a second call to napi_create_environment() crashes the process:

# Check failed: (g_page_allocator) != nullptr.

I found this because the node-api-dotnet project runs multiple embedding test cases in a process, and each test case uses a separate environment instance. With this line removed, the latest PR revision works well.

Was there a reason to add this call to ShutdownProcess()?

Co-authored-by: Gabriel Schulhof <gabrielschulhof@gmail.com>

vmoroz · 2024-03-08T23:41:51Z

@mmomtchev , the code is rebased on the latest main code.

@jasongin

Implemented by @jasongin

reitowo · 2024-09-11T15:04:02Z

Any updates?

vmoroz · 2024-09-11T21:30:10Z

Any updates?

@reitowo , please check the PR #54660 for the progress and the related discussion #23265.
I wonder what is your scenario for the new API and what type of embedding customizations you are looking for?

reitowo · 2024-09-12T01:14:24Z

I was coming from the doc of microsoft's project node & .net interop, just to check the status of this. ☺️

nodejs-github-bot added lib / src Issues and PRs related to general changes in the lib or src directory. needs-ci PRs that need a full CI run. labels Jun 22, 2022

addaleax reviewed Jun 23, 2022

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addaleax added node-api Issues and PRs related to the Node-API. embedding Issues and PRs related to embedding Node.js in another project. labels Jun 23, 2022

mmomtchev mentioned this pull request Jun 24, 2022

N-API: An api for embedding Node in applications #23265

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addaleax requested changes Jun 24, 2022

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mmomtchev force-pushed the napi-libnode branch from 2620063 to 8f64b81 Compare July 5, 2022 22:35

mmomtchev force-pushed the napi-libnode branch 2 times, most recently from 285a377 to 38b7dc8 Compare July 16, 2022 21:54

mmomtchev force-pushed the napi-libnode branch from b8c4b47 to 28abcc0 Compare July 30, 2022 08:26

mmomtchev force-pushed the napi-libnode branch from c2329ae to db147f3 Compare August 31, 2022 16:26

mmomtchev force-pushed the napi-libnode branch 5 times, most recently from f0b96b4 to 33b170d Compare October 10, 2022 20:14

vmoroz reviewed Oct 11, 2022

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jasongin reviewed Mar 8, 2024

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mmomtchev and others added 14 commits March 8, 2024 13:57

node-api: libnode embedding

c55bf50

new linter rules

414c501

remove unintented change

1fb6c8e

restore require/import in main_script

bd223ae

rectify napi_destroy_platform

890bfcb

catch up with main

23ddf96

the linter was not happy with this indentation

213aea4

the underlying libuv issue has been resolved

fc34203

remove the deps/uv patch

a4b2b90

remove the custom main script arg and use execPath

5220a89

Update lib/internal/bootstrap/switches/is_embedded_env.js

a0b3b25

Co-authored-by: Gabriel Schulhof <gabrielschulhof@gmail.com>

adapt to the new embedding API

ccd228b

move code to node_api_embedding.cc

7a566b7

comment typo fix

b7adf10

vmoroz force-pushed the napi-libnode branch from 73b892d to b7adf10 Compare March 8, 2024 23:40

vmoroz added 2 commits March 8, 2024 16:15

delete compiled binary file from test

ebe1c55

Remove ShutdownProcess from napi_destroy_environment

fc3f0ad

Implemented by @jasongin

vmoroz mentioned this pull request Apr 23, 2024

test,doc: enable running embedtest for Windows #52646

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jasongin mentioned this pull request Jun 22, 2024

Please make Node.js embeddable (e.g. libnode) #52289

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jasongin mentioned this pull request Aug 6, 2024

Cannot create multiple NodeJSEnvironment for one NodeJSPlatform microsoft/node-api-dotnet#348

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vmoroz mentioned this pull request Aug 30, 2024

node-api: use c-based api for libnode embedding #54660

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22 tasks

		@@ -6267,6 +6269,95 @@ idempotent.

		This API may only be called from the main thread.

		## Using Node.js as a shared library (`libnode`)

Extend Node-API to libnode #43542

Are you sure you want to change the base?

Extend Node-API to libnode #43542

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mmomtchev commented Jun 22, 2022

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KevinEady commented Jun 24, 2022

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Extend Node-API to `libnode` #43542

Extend Node-API to `libnode` #43542

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