src,napi: add helper for addons to get the event loop #17109

addaleax · 2017-11-17T23:35:49Z

C++ variant

Add a utility functions for addons to use when they need
a reference to the current event loop.

Currently, uv_default_loop() works if the embedder is the
single-threaded default node executable, but even without
the presence of e.g. workers that might not really an API
guarantee for when Node is embedded.

N-API variant

Add a utility functions for addons to use when they need
a reference to the current event loop.

While the libuv API is not directly part of N-API, it
provides a quite stable C API as well, and is tightly
integrated with Node itself.

As a particular use case, without access to the event loop
it is hard to do something interesting from inside a N-API
finalizer function, since calls into JS and therefore virtually
all other N-API functions are not allowed.

Checklist

make -j4 test (UNIX), or vcbuild test (Windows) passes
tests and/or benchmarks are included
documentation is changed or added
commit message follows commit guidelines

Affected core subsystem(s)

node.h, n-api

/cc @nodejs/n-api

Add a utility functions for addons to use when they need a reference to the current event loop. Currently, `uv_default_loop()` works if the embedder is the single-threaded default node executable, but even without the presence of e.g. workers that might not really an API guarantee for when Node is embedded.

Add a utility functions for addons to use when they need a reference to the current event loop. While the libuv API is not directly part of N-API, it provides a quite stable C API as well, and is tightly integrated with Node itself. As a particular use case, without access to the event loop it is hard to do something interesting from inside a N-API finalizer function, since calls into JS and therefore virtually all other N-API functions are not allowed.

addaleax · 2017-11-17T23:42:50Z

CI: https://ci.nodejs.org/job/node-test-commit/14111/

bnoordhuis · 2017-11-18T10:27:32Z

src/node.cc

@@ -4419,6 +4419,11 @@ void RunAtExit(Environment* env) {
 }


+uv_loop_t* GetCurrentEventLoop(v8::Isolate* isolate) {
+  return Environment::GetCurrent(isolate)->event_loop();


Leaks a handle into the caller's scope.

The overload that takes a v8::Isolate* calls Environment::GetCurrent(isolate->GetCurrentContext()) but that won't work when there is no current context or it doesn't have an associated Environment (i.e, non-node context.)

That should be documented because it's the kind of thing that add-ons will run into. You could robustify (def a word) this function by doing:

uv_loop_t* GetCurrentEventLoop(v8::Isolate* isolate) { HandleScope handle_scope(isolate); auto context = isolate->GetCurrentContext(); if (context.IsEmpty()) return nullptr; return Environment::GetCurrent(context); }

That can still crash with a non-node context, though. Maybe we should file a CL with V8 to expose
v8::Context::SlowGetAlignedPointerFromEmbedderData() in order to safely retrieve the Environment pointer.

Yeah, thanks for catching those. Updated with your suggestion!

bnoordhuis · 2017-11-18T10:47:48Z

src/node_api.cc

+napi_status napi_get_uv_event_loop(napi_env env, uv_loop_t** loop) {
+  CHECK_ENV(env);
+  CHECK_ARG(env, loop);
+  *loop = node::GetCurrentEventLoop(env->isolate);


If you make that change, consider adding a sanity check here that loop != nullptr.

I’ve moved the GetCurrentEventLoop call to the napi_env initialization code, I think that should be fine.

bnoordhuis · 2017-11-18T10:49:23Z

test/addons-napi/test_uv_loop/test_uv_loop.cc

+#include <assert.h>
+#include "../common.h"
+
+template<typename T>


Space before <.

bnoordhuis · 2017-11-18T10:51:37Z

test/addons-napi/test_uv_loop/test_uv_loop.cc

+  T* ptr = new T(std::move(cb));
+  uv_loop_t* loop = nullptr;
+  uv_check_t* check = new uv_check_t;
+  check->data = static_cast<void*>(ptr);


Cast-to-void is not necessary.

bnoordhuis · 2017-11-18T10:52:55Z

test/addons-napi/test_uv_loop/test_uv_loop.cc

+  uv_check_start(check, [](uv_check_t* check) {
+    std::unique_ptr<T> ptr {static_cast<T*>(check->data)};
+    T cb = std::move(*ptr);
+    uv_check_stop(check);


Not that it hurts but you don't have to stop the handle if you're closing it anyway.

bnoordhuis · 2017-11-18T11:01:56Z

test/addons-napi/test_uv_loop/test_uv_loop.cc

+  NAPI_CALL(env,
+    napi_create_reference(env, argv[0], 1, &cbref));
+
+  SetImmediate(env, [=]() -> char* {


Just curious, doesn't the compiler infer the return type? Or is this extra protection against someone changing dummy to something with non-static storage?

It gets confused because NAPI_CALL can return NULL, which is 0 in C++ mode, so considered an integer rather than a pointer… I guess that could be fixed by returning an integer type instead, but relying on NULL → 0 seems odd.

addaleax · 2017-11-18T13:02:58Z

Fresh CI: https://ci.nodejs.org/job/node-test-commit/14124/

cjihrig · 2017-11-20T16:12:43Z

doc/api/n-api.md

+N-API provides a function for getting the current event loop associated with
+a specific `napi_env`.
+
+### napi_uv_get_event_loop


This should be napi_get_uv_event_loop I think.

@cjihrig Thanks, fixed!

addaleax · 2017-11-21T07:42:55Z

Landed in c0f3bc2, 9cf3525

Add a utility functions for addons to use when they need a reference to the current event loop. Currently, `uv_default_loop()` works if the embedder is the single-threaded default node executable, but even without the presence of e.g. workers that might not really an API guarantee for when Node is embedded. PR-URL: #17109 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Add a utility functions for addons to use when they need a reference to the current event loop. While the libuv API is not directly part of N-API, it provides a quite stable C API as well, and is tightly integrated with Node itself. As a particular use case, without access to the event loop it is hard to do something interesting from inside a N-API finalizer function, since calls into JS and therefore virtually all other N-API functions are not allowed. PR-URL: #17109 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Add a utility functions for addons to use when they need a reference to the current event loop. Currently, `uv_default_loop()` works if the embedder is the single-threaded default node executable, but even without the presence of e.g. workers that might not really an API guarantee for when Node is embedded. PR-URL: #17109 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Add a utility functions for addons to use when they need a reference to the current event loop. While the libuv API is not directly part of N-API, it provides a quite stable C API as well, and is tightly integrated with Node itself. As a particular use case, without access to the event loop it is hard to do something interesting from inside a N-API finalizer function, since calls into JS and therefore virtually all other N-API functions are not allowed. PR-URL: #17109 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Notable changes: * async\_hooks: - add trace events to async_hooks (Andreas Madsen) #15538 - add provider types for net server (Andreas Madsen) #17157 * console: - console.debug can now be used outside of the inspector (Benjamin Zaslavsky) #17033 * deps: - upgrade libuv to 1.18.0 (cjihrig) #17282 - patch V8 to 6.2.414.46 (Myles Borins) #17206 * module: - module.builtinModules will return a list of built in modules (Jon Moss) #16386 * n-api: - add helper for addons to get the event loop (Anna Henningsen) #17109 * process: - process.setUncaughtExceptionCaptureCallback can now be used to customize behavior for `--abort-on-uncaught-exception` (Anna Henningsen) #17159 - A signal handler is now able to receive the signal code that triggered the handler. (Robert Rossmann) #15606 * src: - embedders can now use Node::CreatePlatform to create an instance of NodePlatform (Cheng Zhao) #16981 * stream: - writable.writableHighWaterMark and readable.readableHighWaterMark will return the values the stream object was instantiated with (Calvin Metcalf) #12860 * **Added new collaborators** * [maclover7](https://github.com/maclover7) Jon Moss * [guybedford](https://github.com/guybedford) Guy Bedford * [hashseed](https://github.com/hashseed) Yang Guo PR-URL: Coming Soon

Notable changes: * async\_hooks: - add trace events to async_hooks (Andreas Madsen) #15538 - add provider types for net server (Andreas Madsen) #17157 * console: - console.debug can now be used outside of the inspector (Benjamin Zaslavsky) #17033 * deps: - upgrade libuv to 1.18.0 (cjihrig) #17282 - patch V8 to 6.2.414.46 (Myles Borins) #17206 * module: - module.builtinModules will return a list of built in modules (Jon Moss) #16386 * n-api: - add helper for addons to get the event loop (Anna Henningsen) #17109 * process: - process.setUncaughtExceptionCaptureCallback can now be used to customize behavior for `--abort-on-uncaught-exception` (Anna Henningsen) #17159 - A signal handler is now able to receive the signal code that triggered the handler. (Robert Rossmann) #15606 * src: - embedders can now use Node::CreatePlatform to create an instance of NodePlatform (Cheng Zhao) #16981 * stream: - writable.writableHighWaterMark and readable.readableHighWaterMark will return the values the stream object was instantiated with (Calvin Metcalf) #12860 * **Added new collaborators** * [maclover7](https://github.com/maclover7) Jon Moss * [guybedford](https://github.com/guybedford) Guy Bedford * [hashseed](https://github.com/hashseed) Yang Guo PR-URL: #17631

Add a utility functions for addons to use when they need a reference to the current event loop. Currently, `uv_default_loop()` works if the embedder is the single-threaded default node executable, but even without the presence of e.g. workers that might not really an API guarantee for when Node is embedded. PR-URL: #17109 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Add a utility functions for addons to use when they need a reference to the current event loop. While the libuv API is not directly part of N-API, it provides a quite stable C API as well, and is tightly integrated with Node itself. As a particular use case, without access to the event loop it is hard to do something interesting from inside a N-API finalizer function, since calls into JS and therefore virtually all other N-API functions are not allowed. PR-URL: #17109 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Notable changes: * deps: * update V8 to 6.2.414.46 (Michaël Zasso) [#16413](#16413) * revert ABI breaking changes in V8 6.2 (Anna Henningsen) [#16413](#16413) * upgrade libuv to 1.19.1 (cjihrig) [#18260](#18260) * re land npm 5.6.0 (Myles Borins) [#18625](#18625) * ICU 60 bump (Steven R. Loomis) [#16876](#16876) * crypto: * Support both OpenSSL 1.1.0 and 1.0.2 (David Benjamin) [#16130](#16130) * warn on invalid authentication tag length (Tobias Nießen) [#17566](#17566) * async_hooks: * update defaultTriggerAsyncIdScope for perf (Anatoli Papirovski) [#18004](#18004) * use typed array stack as fast path (Anna Henningsen) [#17780](#17780) * use scope for defaultTriggerAsyncId (Andreas Madsen) [#17273](#17273) * separate missing from default context (Andreas Madsen) [#17273](#17273) * rename initTriggerId (Andreas Madsen) [#17273](#17273) * deprecate undocumented API (Andreas Madsen) [#16972](#16972) * add destroy event for gced AsyncResources (Sebastian Mayr) [#16998](#16998) * add trace events to async_hooks (Andreas Madsen) [#15538](#15538) * set HTTPParser trigger to socket (Andreas Madsen) [#18003](#18003) * add provider types for net server (Andreas Madsen) [#17157](#17157) * n-api: * add helper for addons to get the event loop (Anna Henningsen) [#17109](#17109) * cli: * add --stack-trace-limit to NODE_OPTIONS (Anna Henningsen) [#16495](#16495) * console: * add support for console.debug (Benjamin Zaslavsky) [#17033](#17033) * module: * add builtinModules (Jon Moss) [#16386](#16386) * replace default paths in require.resolve() (cjihrig) [#17113](#17113) * src: * add helper for addons to get the event loop (Anna Henningsen) [#17109](#17109) * add process.ppid (cjihrig) [#16839](#16839) * http: * support generic `Duplex` streams (Anna Henningsen) [#16267](#16267) * add rawPacket in err of `clientError` event (XadillaX) [#17672](#17672) * better support for IPv6 addresses (Mattias Holmlund) [#14772](#14772) * net: * remove ADDRCONFIG DNS hint on Windows (Bartosz Sosnowski) [#17662](#17662) * process: * fix reading zero-length env vars on win32 (Anna Henningsen) [#18463](#18463) * tls: * unconsume stream on destroy (Anna Henningsen) [#17478](#17478) * process: * improve unhandled rejection message (Madara Uchiha) [#17158](#17158) * stream: * remove usage of *State.highWaterMark (Calvin Metcalf) [#12860](#12860) * trace_events: * add executionAsyncId to init events (Andreas Madsen) [#17196](#17196) PR-URL: #18336

Add a utility functions for addons to use when they need a reference to the current event loop. While the libuv API is not directly part of N-API, it provides a quite stable C API as well, and is tightly integrated with Node itself. As a particular use case, without access to the event loop it is hard to do something interesting from inside a N-API finalizer function, since calls into JS and therefore virtually all other N-API functions are not allowed. PR-URL: nodejs#17109 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Add a utility functions for addons to use when they need a reference to the current event loop. While the libuv API is not directly part of N-API, it provides a quite stable C API as well, and is tightly integrated with Node itself. As a particular use case, without access to the event loop it is hard to do something interesting from inside a N-API finalizer function, since calls into JS and therefore virtually all other N-API functions are not allowed. Backport-PR-URL: #19447 PR-URL: #17109 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Notable changes: * deps: * update V8 to 6.2.414.46 (Michaël Zasso) [nodejs#16413](nodejs#16413) * revert ABI breaking changes in V8 6.2 (Anna Henningsen) [nodejs#16413](nodejs#16413) * upgrade libuv to 1.19.1 (cjihrig) [nodejs#18260](nodejs#18260) * re land npm 5.6.0 (Myles Borins) [nodejs#18625](nodejs#18625) * ICU 60 bump (Steven R. Loomis) [nodejs#16876](nodejs#16876) * crypto: * Support both OpenSSL 1.1.0 and 1.0.2 (David Benjamin) [nodejs#16130](nodejs#16130) * warn on invalid authentication tag length (Tobias Nießen) [nodejs#17566](nodejs#17566) * async_hooks: * update defaultTriggerAsyncIdScope for perf (Anatoli Papirovski) [nodejs#18004](nodejs#18004) * use typed array stack as fast path (Anna Henningsen) [nodejs#17780](nodejs#17780) * use scope for defaultTriggerAsyncId (Andreas Madsen) [nodejs#17273](nodejs#17273) * separate missing from default context (Andreas Madsen) [nodejs#17273](nodejs#17273) * rename initTriggerId (Andreas Madsen) [nodejs#17273](nodejs#17273) * deprecate undocumented API (Andreas Madsen) [nodejs#16972](nodejs#16972) * add destroy event for gced AsyncResources (Sebastian Mayr) [nodejs#16998](nodejs#16998) * add trace events to async_hooks (Andreas Madsen) [nodejs#15538](nodejs#15538) * set HTTPParser trigger to socket (Andreas Madsen) [nodejs#18003](nodejs#18003) * add provider types for net server (Andreas Madsen) [nodejs#17157](nodejs#17157) * n-api: * add helper for addons to get the event loop (Anna Henningsen) [nodejs#17109](nodejs#17109) * cli: * add --stack-trace-limit to NODE_OPTIONS (Anna Henningsen) [nodejs#16495](nodejs#16495) * console: * add support for console.debug (Benjamin Zaslavsky) [nodejs#17033](nodejs#17033) * module: * add builtinModules (Jon Moss) [nodejs#16386](nodejs#16386) * replace default paths in require.resolve() (cjihrig) [nodejs#17113](nodejs#17113) * src: * add helper for addons to get the event loop (Anna Henningsen) [nodejs#17109](nodejs#17109) * add process.ppid (cjihrig) [nodejs#16839](nodejs#16839) * http: * support generic `Duplex` streams (Anna Henningsen) [nodejs#16267](nodejs#16267) * add rawPacket in err of `clientError` event (XadillaX) [nodejs#17672](nodejs#17672) * better support for IPv6 addresses (Mattias Holmlund) [nodejs#14772](nodejs#14772) * net: * remove ADDRCONFIG DNS hint on Windows (Bartosz Sosnowski) [nodejs#17662](nodejs#17662) * process: * fix reading zero-length env vars on win32 (Anna Henningsen) [nodejs#18463](nodejs#18463) * tls: * unconsume stream on destroy (Anna Henningsen) [nodejs#17478](nodejs#17478) * process: * improve unhandled rejection message (Madara Uchiha) [nodejs#17158](nodejs#17158) * stream: * remove usage of *State.highWaterMark (Calvin Metcalf) [nodejs#12860](nodejs#12860) * trace_events: * add executionAsyncId to init events (Andreas Madsen) [nodejs#17196](nodejs#17196) PR-URL: nodejs#18336

jinfeihan57 · 2022-08-10T04:16:21Z

@addaleax Is napi_get_uv_event_loop() thread safe?

addaleax · 2022-08-10T10:36:48Z

@jinfeihan57 No. None of the Node-API methods that aren’t explicitly designed for usage with multithreading are thread-safe.

jinfeihan57 · 2022-08-11T07:32:23Z

@jinfeihan57 No. None of the Node-API methods that aren’t explicitly designed for usage with multithreading are thread-safe.

That means I can't call it from another thread, Am I right?
uv loop is a global resource Can you make it thread safe?

addaleax added 2 commits November 18, 2017 00:28

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. lib / src Issues and PRs related to general changes in the lib or src directory. labels Nov 17, 2017

bnoordhuis reviewed Nov 18, 2017

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addaleax closed this Nov 21, 2017

addaleax deleted the get-current-loop branch November 21, 2017 07:43

addaleax removed the author ready PRs that have at least one approval, no pending requests for changes, and a CI started. label Nov 28, 2017

MylesBorins mentioned this pull request Dec 12, 2017

v9.3.0 proposal #17631

Merged

gibfahn added dont-land-on-v6.x labels Jan 15, 2018

MylesBorins mentioned this pull request Apr 16, 2018

v6.14.2 proposal #19996

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src,napi: add helper for addons to get the event loop #17109

src,napi: add helper for addons to get the event loop #17109

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jinfeihan57 commented Aug 11, 2022

src,napi: add helper for addons to get the event loop #17109

src,napi: add helper for addons to get the event loop #17109

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addaleax commented Nov 17, 2017

C++ variant

N-API variant

Checklist

Affected core subsystem(s)

addaleax commented Nov 17, 2017

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