PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Concurrent writes to the same fd are generally not ideal,
since it’s not generally guaranteed that data from those
writes will end up on disk in the right order.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Fixes: #22042

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

A forward declaration suffices and means that the tracing
agent header and its dependencies don’t need to be included
in nearly every Node.js file.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Avoid unnecessary copies/extra operations & align with our style guide,
and add protection against throwing getters.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Avoid unnecessary operations, add a bit of documentation,
and turn the `ClientHandle` smart pointer alias into a real
class.

This should allow de-coupling the unnecessary combination of
a single specific `file_writer` from `Agent`.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

The agent code is supposed to manage multiple writers/clients.
Adding the default writer into the mix breaks that encapsulation.
Instead, manage default options through a separate "virtual"
default client handle, and keep the file writer management
all to the actual users.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Otherwise this would have crashed the process.
In particular, checking the return value of an libuv call against `-1`
was invalid to begin with, as libuv uses it to propagate the
error code.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Clean up resources when tearing down the tracing agent.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Run the initialization for the file trace writer’s `uv_async_t`s
on the same thread as `uv_run()` for their loop to avoid race
conditions.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Close existing file descriptors before overriding
the field with new ones.

Also, use `nullptr` as the loop for these synchronous
operations, since they do not run on the same thread
as the `uv_run()` call for the previously used loop.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Concurrent writes to the same fd are generally not ideal,
since it’s not generally guaranteed that data from those
writes will end up on disk in the right order.

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Fixes: #22042

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>