inspector: fix process._debugEnd() for inspector #12777

eugeneo · 2017-05-01T20:42:41Z

This change ensures that the WebSocket server can be stopped
(and restarted if needed) buy calling process._debugEnd.

Checklist

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

Affected core subsystem(s)

inspector: fixes around WS server stopping and (re)starting.

TimothyGu · 2017-05-02T00:44:23Z

This needs a rebase, and what is the nature of process._debugEnd()? Are users allowed to call it themselves or is it a private API?

823639792 · 2017-05-02T08:23:09Z

I need it

eugeneo · 2017-05-02T15:46:57Z

@TimothyGu this is not a new API - it was working with the old debugger. I did not know about this API until #12559 - so now I am fixing the issues.

There are some genuine bugs that this API uncovered - those really need to be fixed.

eugeneo · 2017-05-02T15:47:25Z

(I am looking into CI failures, looks like some new bugs were introduced)

TimothyGu · 2017-05-02T16:44:55Z

While I agree that we should at the minimum make the function working again under Inspector, I think we should consider making it fully public (document it and rename it to process.debugEnd) if it is deemed to be useful, especially now that it seems some people are using it.

eugeneo · 2017-05-02T17:18:53Z

As this PR is not introducing/altering existing API, I would like to proceed with it in its current form (well, after I figure out how to fix intermittent issues :) )

Feel free to open a separate issue about the public API. I expect a lot of discussions there...

eugeneo · 2017-05-02T21:56:58Z

All issues seem to be resolved. CI run: https://ci.nodejs.org/job/node-test-pull-request/7810/

refack · 2017-05-02T23:03:19Z

src/inspector_agent.cc

+  static_cast<Agent*>(handle->data)->StartIoThread(false);
+}
+
+void StartIoCallback(Isolate* isolate, void* agent) {


Why is there an Isolate* isolate arg?

That's "InterruptCallback" typedef - https://github.com/nodejs/node/blob/master/deps/v8/include/v8.h#L5994

refack · 2017-05-02T23:18:56Z

test/inspector/inspector-helper.js

-  }).on('close', () => assert(this.expectClose_, 'Socket closed prematurely'));
+  }).on('close', () => {
+    assert(this.expectClose_, 'Socket closed prematurely');
+    this.closeCallback_ && this.closeCallback_();


I'm just trying to grok the code...
Who will set this.closeCallback_?

This test "framework" is really messy - I am trying to clean it up, but have not yet achieved the stage to create a pull request...

Currently the callback is set in sendCommandsAndExpectClose, e.g. when there's a need to handle connection closing and not just assert.

refack

I need another run through the code, it's been 3 years since I was there this...
Could you summarize the change in 3-4 sentences

refack · 2017-05-02T23:21:43Z

src/inspector_io.cc

@@ -89,13 +90,18 @@ void HandleSyncCloseCb(uv_handle_t* handle) {
 int CloseAsyncAndLoop(uv_async_t* async) {
  bool is_closed = false;
  async->data = &is_closed;
-  uv_close(reinterpret_cast<uv_handle_t*>(async), HandleSyncCloseCb);


Help me here.
What happened to HandleSyncCloseCb?

Great catch! Thank you. I removed it by mistake together with debug statements when debugging the intermittent test failures :/

refack · 2017-05-02T23:26:16Z

If I get the jist, we need to stop the InspectorAgent better, as it wasn't fully implemented during the transition?

refack · 2017-05-02T23:28:32Z

test/inspector/test-on-off.js

+    ]).expectShutDown(0);
+}
+
+const script = 'process._debugEnd();' +


Is this a new functionality? detaching and reattaching?

It is not a new functionality. Both APIs were already there (_debugProcess is meant to attach to other processes - but looks like it can be made to work on self just fine).

_debugProcess sends a signal on Posix systems. It is the function used to attach to processes that were not started with --inspect.
__debugEnd stops the agent. Looks like it had been there for ages, personally I am not sure why it is needed :)

personally I am not sure why it is needed :)

Which one _debugProcess, I assume?

Or am I missing something?

_debugProcess is useful, frontends use it to attach to running instances.

__debugEnd, on the other hand, can only be called on self so the application needs to explicitly "want" to make itself undebuggable. I am not sure why...

Why the complex script?
Run once with just _debugEnd since this is the change.
We want to know if just this is failing, now it could fail on any of the two.
You can do a second run with this script.

But, but, but, that is what you're fixing.... 😕

You're just doing it for @823639792?

Complex script - I noticed that starting inspector after it had been stopped crashed the Node, so some test coverage definitely helps.

_debugEnd - the goal here is to ensure that inspector can cleanly stop. There were some genuine bugs and race conditions that need to be addressed.

Sure, so do two tests...

eugeneo · 2017-05-02T23:28:42Z

@refack Right. Initial inspector prototype was a fork of the debug_agent.cc - so it compiled but I did not pay much attention to Stop (e.g. the assumption was it is only called during the shutdown).

refack · 2017-05-02T23:53:06Z

@eugeneo can you rename this PR to fix process._debugEnd() or transition process._debugEnd() to inspector

eugeneo · 2017-05-03T17:14:24Z

@refack I updated commit message and PR title. I also added a test case that only stops the inspector.

refack · 2017-05-03T19:47:16Z

test/inspector/test-off-no-session.js

+  harness.expectShutDown(42);
+}
+
+helper.startNodeForInspectorTest(testStop, '--inspect',


shouldn't it be '--inspect-brk'

No. That test does not wait for the session. The tests cover shutting down the inspector with or without the session.

Just wondering because of the failures....

refack · 2017-05-03T19:49:04Z

Do You have any idea why is fails only on aix & feeBSD?

refack · 2017-05-03T20:32:05Z

test/inspector/test-off-with-session-then-on.js

+
+const script = 'process._debugEnd();' +
+               'process._debugProcess(process.pid);' +
+               'process._debugEnd();' +


it this line new?

I am testing if this fixes the failures. Server is starting (and printing out the message) on a background thread so I suspect the reason test fails is because process shuts down too fast. _debugEnd synchronizes the threads.

That was my guess...

eugeneo · 2017-05-03T23:29:06Z

@refack looks like process exits before the stdio buffers are flushed - adding console.log fixes the failure (this is BSD stress test - https://ci.nodejs.org/job/node-stress-single-test/1192/nodes=freebsd10-64/)

I uploaded updated test.

eugeneo · 2017-05-03T23:40:01Z

Still failing on AIX: https://ci.nodejs.org/job/node-stress-single-test/1193/nodes=aix61-ppc64/console, investigating...

eugeneo · 2017-05-05T18:09:24Z

Looks like the only way to fix the test once and for all would be to add the delay - which I won't do as it increases duration of the test run for little gain. This is AIX stress test with arbitrary delay added: https://ci.nodejs.org/job/node-stress-single-test/nodes=aix61-ppc64/1198/

What I uploaded here is to stop checking for the inspector startup message. If the inspector actually fails to start there will be crash so checking the process exit code should be enough.

refack · 2017-05-05T18:18:11Z

What I uploaded here is to stop checking for the inspector startup message. If the inspector actually fails to start there will be crash so checking the process exit code should be enough.

Sounds reasonable. There's an explicit test for that in #11207

eugeneo · 2017-05-09T17:17:15Z

CI all green: https://ci.nodejs.org/job/node-test-pull-request/7903/

eugeneo · 2017-05-11T17:17:47Z

@refack, @sam-github please let me know if I have not addressed any of your comments - I'm a bit confused with the GitHub UI...

CI is green: https://ci.nodejs.org/job/node-test-pull-request/7974/

sam-github · 2017-05-11T17:57:03Z

@eugeneo you didn't respond to #12777 (comment), and yes, the new review UI has some problems.

eugeneo · 2017-05-11T20:48:21Z

@sam-github

I'm specifically looking for ways to start and stop the debugger programmatically, this seems to only have stop (called "end", I assume that is historical, because its not an obvious name)

True, these are the legacy APIs. The closest way to (re)start debugger is process._debugProcess(process.pid). It uses IPC (signals on *nix and debug API on Windows) but seems to work well if called on self.

Its not clear whether start/stop can be done with #12263, or whether these _ prefixed APIs should be documented, or perhaps renamed or even moved to the inspector module.

API design is out of scope for this PR. #12263 also deals with the JS bindings for the session management - but it will be trivial to add some nicer start/stop APIs to inspector module, if need be.

sam-github

A couple small nits, but basically LGTM

sam-github · 2017-05-11T21:04:41Z

src/inspector_agent.cc

    io_->Stop();
+    io_.reset();


I have trouble understanding Node core C++ conventions, does it makes sense that Stop() is upper case, and reset() is lower case @addaleax ?

Node core is usually more UpperSnakeCase() for methods, but reset() doesn’t come from Node core. I think this is okay.

Stop is InspectorIo::Stop which is Node.
reset is std::unique_ptr::reset which is STL...

sam-github · 2017-05-11T21:06:51Z

src/inspector_io.cc

@@ -96,6 +97,12 @@ int CloseAsyncAndLoop(uv_async_t* async) {
  return uv_loop_close(async->loop);
 }

+void ReleasePairOnAsyncClose(uv_handle_t* async) {
+  AsyncAndAgent* pair = node::ContainerOf(&AsyncAndAgent::first,
+                                        reinterpret_cast<uv_async_t*>(async));


I think this line is supposed to be indented to line up after the parentheses (that you have to do this after changing the name of the type in the line before is why I don't like this style, but its the node style)

Done, thanks!

sam-github · 2017-05-11T21:08:41Z

src/inspector_io.cc

    DispatchMessages();
  }
  return true;
 }

 void InspectorIo::Stop() {
+  CHECK(state_ == State::kAccepting || state_ == State::kConnected);


eugeneo · 2017-05-11T21:53:52Z

CI: https://ci.nodejs.org/job/node-test-pull-request/7974/

sam-github · 2017-05-12T15:14:29Z

LGTM, @refack PTAL

eugeneo · 2017-05-17T17:44:42Z

@refack - gentle ping, please take another look :)

sam-github · 2017-05-19T16:30:56Z

@refack PTAL

What I've seen was good

refack · 2017-05-19T19:56:50Z

Sorry, for some reason your pings got filtered out from my email list.

sam-github · 2017-05-19T19:58:56Z

@eugeneo noticed a typo in the commit message s/buy/by

refack

LGTM, pending CI and commit message nits.

refack · 2017-05-19T20:07:15Z

Fresh CI: https://ci.nodejs.org/job/node-test-commit/10022/

sam-github · 2017-05-19T20:10:04Z

Failures displayed in the PR may not be accurate, check @refack 's build on ci (I started a build 30 seconds after, and cancelled it, so I think the cancelled status is what is showing up in the github view).

refack · 2017-05-19T20:12:55Z

PS fedora22 is backlogged with something like 6hr work, if it's the only one left, I say land.
https://ci.nodejs.org/job/node-test-commit-linux/nodes=fedora22/

sam-github · 2017-05-19T20:45:13Z

Thanks @refack. I'll let @eugeneo land it so he can do any fixups he wants on the way in.

eugeneo · 2017-05-22T17:32:43Z

CI: https://ci.nodejs.org/job/node-test-pull-request/8200/

eugeneo · 2017-05-22T17:41:13Z

I forgot to update the commit message to include PR-URL and Reviewed by. Does this justify revert?

refack · 2017-05-22T17:42:11Z

Force push, and apologize in the IRC (that's the procedure)

refack · 2017-05-22T17:43:49Z

https://github.com/nodejs/node/blob/master/COLLABORATOR_GUIDE.md#i-just-made-a-mistake

eugeneo · 2017-05-22T17:44:50Z

Done, thanks! Will push the proper commit.

eugeneo · 2017-05-22T18:20:55Z

Landed as 5c26378

sam-github · 2017-05-23T13:57:18Z

@eugeneo

** CID 169616:  Resource leaks  (CTOR_DTOR_LEAK)
/src/inspector_io.cc: 179 in node::inspector::InspectorIo::InspectorIo(node::Environment *, v8::Platform *, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&, const node::DebugOptions &, bool)()


________________________________________________________________________________________________________
*** CID 169616:  Resource leaks  (CTOR_DTOR_LEAK)
/src/inspector_io.cc: 179 in node::inspector::InspectorIo::InspectorIo(node::Environment *, v8::Platform *, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&, const node::DebugOptions &, bool)()
173                              : options_(options), thread_(), delegate_(nullptr),
174                                state_(State::kNew), parent_env_(env),
175                                io_thread_req_(), platform_(platform),
176                                dispatching_messages_(false), session_id_(0),
177                                script_name_(path),
178                                wait_for_connect_(wait_for_connect) {
>>>     CID 169616:  Resource leaks  (CTOR_DTOR_LEAK)
>>>     The constructor allocates field "main_thread_req_" of "node::inspector::InspectorIo" but the destructor and whatever functions it calls do not free it.
179       main_thread_req_ = new AsyncAndAgent({uv_async_t(), env->inspector_agent()});
180       CHECK_EQ(0, uv_async_init(env->event_loop(), &main_thread_req_->first,
181                                 InspectorIo::MainThreadAsyncCb));
182       uv_unref(reinterpret_cast<uv_handle_t*>(&main_thread_req_->first));
183       CHECK_EQ(0, uv_sem_init(&start_sem_, 0));
184     }

This change ensures that the WebSocket server can be stopped (and restarted if needed) buy calling process._debugEnd. PR-URL: #12777 Fixes: #12559 Reviewed-By: Sam Roberts <vieuxtech@gmail.com> Reviewed-By: Refael Ackermann <refack@gmail.com>

eugeneo · 2017-05-23T18:00:35Z

@sam-github it actually gets freed in ReleasePairOnAsyncClose that is called asynchronously after the request is closed from InspectorIo::~InspectorIo

This change ensures that the WebSocket server can be stopped (and restarted if needed) buy calling process._debugEnd. PR-URL: #12777 Fixes: #12559 Reviewed-By: Sam Roberts <vieuxtech@gmail.com> Reviewed-By: Refael Ackermann <refack@gmail.com>

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. dont-land-on-v4.x inspector Issues and PRs related to the V8 inspector protocol labels May 1, 2017

eugeneo added the dont-land-on-v6.x label May 2, 2017

eugeneo requested review from refack and removed request for refack May 2, 2017 21:57

refack reviewed May 2, 2017

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refack previously requested changes May 2, 2017

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refack reviewed May 2, 2017

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eugeneo changed the title ~~inspector: implement process._debugEnd()~~ inspector: fix process._debugEnd() for inspector May 3, 2017

refack reviewed May 3, 2017

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sam-github approved these changes May 11, 2017

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refack approved these changes May 19, 2017

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eugeneo closed this May 22, 2017

eugeneo deleted the fix__debugEnd branch May 22, 2017 17:36

eugeneo merged commit 9cd991d into nodejs:master May 22, 2017

jasnell mentioned this pull request May 28, 2017

8.0.0 Release Proposal #12220

Closed

inspector: fix process._debugEnd() for inspector #12777

inspector: fix process._debugEnd() for inspector #12777

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eugeneo commented May 1, 2017

Checklist

Affected core subsystem(s)

TimothyGu commented May 2, 2017

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