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Report async tasks to V8 Inspector #13870

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Closed

Report async tasks to V8 Inspector #13870

wants to merge 5 commits into from

Commits on Aug 17, 2017

  1. process: add "process.bits" property 

    Expose a new property that can be used by JS-land code to detect
whether Node.js was compiled in 32bit or 64bit mode. This is important
when converting from JavaScript numbers to raw pointers: JavaScript
always stores numbers as 64bit, but the pointer size is 32 bits or
64 bits depending on the platform.
    @bajtos @TimothyGu
    bajtos authored and TimothyGu committed Aug 17, 2017
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  2. inspector: enable async stack traces 

    Implement a special async_hooks listener that forwards information
about async tasks to V8Inspector asyncTask* API, thus enabling
DevTools feature "async stack traces".

The feature is enabled only on 64bit platforms due to a technical
limitation of V8 Inspector: inspector uses a pointer as a task id,
while async_hooks use 64bit numbers as ids.

To avoid performance penalty of async_hooks when not debugging,
the new listener is enabled only when the process enters a debug mode:

 - When the process is started with `--inspect` or `--inspect-brk`,
   the listener is enabled immediately and async stack traces
   lead all the way to the first tick of the event loop.

 - When the debug mode is enabled via SIGUSR1 or `_debugProcess()`,
   the listener is enabled together with the debugger. As a result,
   only async operations started after the signal was received
   will be correctly observed and reported to V8 Inspector. For example,
   a `setInterval()` called in the first tick of the event will not be
   shown in the async stack trace when the callback is invoked. This
   behaviour is consistent with Chrome DevTools.

Last but not least, this commit fixes handling of InspectorAgent's
internal property `enabled_` to ensure it's set back to `false`
after the debugger is deactivated (typically via `process._debugEnd()`).
    @bajtos @TimothyGu
    bajtos authored and TimothyGu committed Aug 17, 2017
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  3. test: fix inspector helper port sniffing

    @TimothyGu
    TimothyGu committed Aug 17, 2017
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  4. fixup! convert tests

    @TimothyGu
    TimothyGu committed Aug 17, 2017
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  5. fixup! make tests more robust

    @TimothyGu
    TimothyGu committed Aug 17, 2017
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