node: extract node env initialization out of process initialization

[petkaantonov]

This will enable implementing a worker class that is backed by a thread instead of a separate process.

/cc @bnoordhuis

P.S. I saw your todo comments about using uv_default_loop, I was thinking why not have the main thread use the default loop and workers use their own loops?

[bnoordhuis]

Style: void* arg

[bnoordhuis]

If StartNodeInstance() is not used elsewhere, it should be static or inline (they amount to the same thing, non-external linkage.)

[bnoordhuis]

I saw your todo comments about using uv_default_loop, I was thinking why not have the main thread use the default loop and workers use their own loops?

I'm not sure what comment that was but it sounds reasonable.

[vkurchatkin]

Why do we need another class for this? Isn't Environment enough?

[petkaantonov]

Addressed @bnoordhuis comments, I also added an internal CreateEnvironment overload since in the future we will need to know in env too whether it's the main thread or a worker one.

Why do we need another class for this? Isn't Environment enough?

Instances of this class will be the data argument passed to uv_create_thread, I think it's cleaner if we create Environment while already executing in the thread the environment will belong to.

[bnoordhuis]

Looking at this again, I think it should be left to the caller to clean up the uv_loop_t. Calling uv_loop_delete() is not safe because we don't know if the loop was created with uv_loop_new() or uv_loop_init().

[bnoordhuis]

LGTM with comments.

[petkaantonov]

Addressed comments, rebased to v1.x and squashed

[petkaantonov]

ping

[bnoordhuis]

Indent error.

[bnoordhuis]

LGTM apart from a style nit. Land at will.

[chrisdickinson]

Merged in 4ae64b2. Thanks!

[rvagg]

this feels like something that should go into Notable items in the 1.5.0 release notes but I don't really know how best to characterise it for casual readers. Does somebody want to take a stab at a description in #1060 for me before this goes out?

[bnoordhuis]

It's still completely internal, add-ons or embedders can't use it yet.