[C++] Investigate spawning arbitrary callbacks from StopToken

[asfimport]

In some situations, we may want to forward stop requests to external runtimes, e.g. gRPC (see #10318 ), without polling.

Ideally, one may temporarily add a callback to a StopToken. This bears complications, especially in the case where the stop request comes from a signal handler.

Reporter: Antoine Pitrou / @pitrou

Related issues:

• [C++] Use self-pipe in signal-receiving StopSource (depends upon)
• [C++] Create a signal-safe self-pipe abstraction (depends upon)

_{Note: This issue was originally created as ARROW-12938. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
Possibly related: ARROW-11916

[asfimport]

David Li / @lidavidm:
Related ML discussion: https://lists.apache.org/thread/c79zvztw2rmyt4t8mf7ft760f9wt6wcs

[asfimport]

Todd Farmer / @toddfarmer:
This issue was last updated over 90 days ago, which may be an indication it is no longer being actively worked. To better reflect the current state, the issue is being unassigned per project policy. Please feel free to re-take assignment of the issue if it is being actively worked, or if you plan to start that work soon.

[asfimport]

David Li / @lidavidm:
It looks like this should be possible now, using a self-pipe and a thread? There'll also be a little fiddliness to register and unregister callbacks (assuming a StopToken is meant to be sharable among multiple actions).

[asfimport]

Antoine Pitrou / @pitrou:
Yes, this is possible even without a separate thread. But you're right there's some API design work.