improvement(core): handle more OS signals and broadcast them

[onur-ozkan]

Makes KDF to broadcast (through streaming manager) OS signal before the graceful shutdown.

Also, refactors the spawn_ctrl_c_handler function to cover more signals in a more generic way (can handle more signals easily when needed).

The event activation RPC:

curl --url "http://127.0.0.1:7783" --data '{
  "userpass":"'$userpass'",
  "method":"stream::shutdown_signal::enable",
  "mmrpc":"2.0",
  "params": {},
  "id": "'$client_id'"
}'

The broadcasted message:

for the signals we can't gracefully shutdown, the message will be "UNKNOWN($id_of_the_signal)".

This feature isn't supported on Windows, and doesn't run on Web for obvious reasons.

[dimxy]

LGTM

[onur-ozkan]

There is a new feature since your approval. @dimxy

[mariocynicys]

thanks, all comments below are nits.
LGTM!

[mariocynicys]

since we intend to handle any signal, shouldn't we init our signal hook with all signals (if there is a catch all thing).

not really a problem since we have the important signals covered, but looking at this, the unknown signal line would never be triggered (though i would prefer it like that instead of unreachable! so i don't have a problem with that either).

[onur-ozkan]

since we intend to handle any signal

No, not any signal. We can't handle every signal (e.g., we can't handle SIGKILL). I wanted to handle ones (the obvious ones) that can be handled.

[CharlVS]

@onur-ozkan thanks for this! It will make a significant difference in the GUI needing to poll to get wallet status.

This feature isn't supported on Windows, and doesn't run on Web for obvious reasons.

I'm assuming your streaming event was intended as a QoL addition to the existing PR, initially fixing an iOS-specific issue, but it is worth adding the catching to Windows as well. We won't encounter the file descriptor limit issue on non-iOS platforms, but there may be other reasons KDF shuts down via a signal. e.g. user terminates the KDF process in the task manager.

[onur-ozkan]

I'm assuming your streaming event was intended as a QoL addition to the existing PR, initially fixing an iOS-specific issue, but it is worth adding the catching to Windows as well. We won't encounter the file descriptor limit issue on non-iOS platforms, but there may be other reasons KDF shuts down via a signal. e.g. user terminates the KDF process in the task manager.

Yeah, we should support Windows too but it would require a broader work. We can handle that later (I guess when it becomes very necessary?).