v7.x backport: src: add tracing controller

[matthewloring]

This commit adds support for trace-event tracing to Node.js. It provides
a mechanism to centralize tracing information generated by V8, Node
core, and userspace code. It includes:

• A trace writer responsible for serializing traces and cycling the
  output files so that no individual file becomes to large.
• A buffer for aggregating traces to allow for batched flushes.
• An agent which initializes the tracing controller and ensures that
  trace serialization is done on a separate thread.
• A set of macros for generating trace events.
• Tests and documentation.

Author: Raymond Kang [email protected]
Author: Kelvin Jin [email protected]
Author: Matthew Loring [email protected]
Author: Jason Ginchereau [email protected]

PR-URL: #9304

Reviewed-By: Trevor Norris [email protected]
Reviewed-By: Michael Dawson [email protected]
Reviewed-By: Josh Gavant [email protected]

[richardlau]

Should #10959 be included in this or backported separately?

[joshgav]

There were some concerns in #9304 we wanted to address before including this in a release, in particular making the log output location configurable (#9304 (comment)).

/cc @jasongin @nodejs/diagnostics

[matthewloring]

@joshgav The use of the --trace-events-enabled flag prints Warning: Trace event is an experimental feature and could change at any time.. There are many enhancements that would improve trace event reporting/usage but I'm not sure which should hold it back from a release. I think it provides enough value in its current form to release but I don't mind holding off if others have strong opinions.

@richardlau I think there are a few dependent PRs that can land if this one does. They can probably be opened separately if/once this has gone in.

[italoacasas]

@matthewloring can you rebase please

[matthewloring]

@italoacasas All rebased.

[matthewloring]

@joshgav Can this land?

[matthewloring]

It also looks like the trace event configuration options landed in the node --help output. Not sure how they got into the release without this PR.

[joshgav]

@matthewloring

@joshgav Can this land?

LGTM

@italoacasas do the approvals/LGTMs from the original PR count for backports too? Or do backports need another approval?

[joshgav]

Rubber stamp LGTM from reviewing original PR.

[italoacasas]

@joshgav same process. we need LGTM here.

[italoacasas]

This is not landing in version 7 staging, because of 4b8b7e9. @matthewloring can you update the backport again please, and sorry for the inconvenience.

[joshgav]

Rebased cleanly (and force-pushed to @matthewloring's branch). Still need another LGTM I think? @nodejs/diagnostics PTAL.

[matthewloring]

LGTM but I'm not sure I count since I opened the PR.

[italoacasas]

Landed

[Trott]

Adding dont-land-on for v4.x and v6.x as this is a backport of a semver-minor. /cc @MylesBorins (2 of 3)

[jasnell]

selected semver-minor's can land on LTS branches. It people feel that it is worthwhile, then mention @nodejs/lts in the comments and a decision can be made.

[matthewloring]

This change is not compatible with the versions of V8 in 4.x and 6.x.