How to restart a module with code?

Tianzhu · November 14, 2023, 6:01am

I have a module defined as below. In the shell, I can run “myModule stop/start” to restart the module. Is there a way to do it with code (e.g., in a mavlink message, I want to restart myModule)? Thanks!

class myModule: public ModuleBase<myModule>, public ModuleParams, public px4::ScheduledWorkItem {
}

Tianzhu · November 14, 2023, 5:51pm

Looks like we may be able to send the command to the main px4 instance (server) via socket.

github.com

PX4/PX4-Autopilot/blob/58d2badf9f340bd4e755a08d2f9e716bf4ec906d/platforms/posix/src/px4/common/px4_daemon/server.cpp#L85


      
          }
          
          int
          Server::start()
          {
          	std::string sock_path = get_socket_path(_instance_id);
          
          	// Delete socket in case it exists already.
          	unlink(sock_path.c_str());
          
          	_fd = socket(AF_UNIX, SOCK_STREAM, 0);
          
          	if (_fd < 0) {
          		PX4_ERR("error creating socket");
          		return -1;
          	}
          
          	sockaddr_un addr = {};
          	addr.sun_family = AF_UNIX;
          	strncpy(addr.sun_path, sock_path.c_str(), sizeof(addr.sun_path) - 1);

And the doc also mentions that. But I couldn’t find some example how to send such command from a client.

The server listens on a socket, to which clients can connect and send a command. The server then sends the output and return code back to the client

JulianOes · November 14, 2023, 6:12pm

You can do system calls to run other commands.

I’ve just done that here: Add I2C driver launcher by julianoes · Pull Request #22047 · PX4/PX4-Autopilot · GitHub

And note that it also requires some px4board and defconfig changes. It’s all in the pull request.

Tianzhu · November 14, 2023, 9:01pm

Thanks for the reply, @JulianOes. Do you mean something like this?

system("/opt/px4/bin/px4-muModule stop");
system("/opt/px4/bin/px4-muModule start");

JulianOes · November 14, 2023, 9:27pm

Oh, my PR is for the Pixhawks, so NuttX based. For SITL on Linux it might look somewhat like what you suggest, as long as you have the paths right.

Tianzhu · November 14, 2023, 9:32pm

Got it, thank you so much, @JulianOes!