Iterate mode 2 (regular iterate, comms driven mail) does not work as documented

[crmoore]

Iterate is delayed after receiving mail. Even indefinitely if mail is regular and faster than app_tick.

OnNewMail is always called as soon as mail arrives, even if max_app_tick should be limiting it.

Reproduction:

• A simple MOOSApp that subscribes to a single variable. Run with iterate_mode=2, app_tick=1, max_app_tick=1. Print a message on each Iterate and OnNewMail.
• publish data at 2hz with umm
• Observe behavior of the subscriber app: OnNewMail is called at 2hz, Iterate is not called.

Test app

• Run with main --moos_app_tick=1 --moos_max_app_tick=1 --moos_iterate_mode=2
• Run umm with umm -p=TEST_VAR:10@2

#include <MOOS/libMOOS/App/MOOSApp.h>

#include <iostream>
#include <chrono>

using namespace std::chrono;

class TestApp : public CMOOSApp
{
	bool OnConnectToServer() override;
	bool OnNewMail(std::list<CMOOSMsg>& Main) override;
	bool Iterate() override;

private:
	steady_clock::time_point iter_time, mail_time;
	int mail_count{0}, iter_count{0};
};

int main(int argc, char** argv){

	TestApp App;

	std::cerr << "Running...\n";
	App.Run("TestApp", "mission.moos", argc, argv);
	std::cerr << "Done\n";
}

bool TestApp::OnConnectToServer() {
	std::cerr << "OnConnectToServer\n";

	Register("TEST_VAR", 0);
	return true;
}

bool TestApp::OnNewMail(std::list<CMOOSMsg>& mail) {
	auto now = steady_clock::now();
	double dt_s = duration_cast<duration<double>>(now - mail_time).count();
	mail_time = now;

	std::cerr << "\nOnNewMail " << mail_count++
	          << " " << dt_s << ": " + std::to_string(mail.size()) + "\n";

	for(CMOOSMsg& msg : mail){
		msg.Trace();
	}

	return true;
}


bool TestApp::Iterate() {
	auto now = steady_clock::now();
	double dt_s = duration_cast<duration<double>>(now - iter_time).count();
	iter_time = now;

	std::cerr << "\nIterate " << iter_count++ << " " << dt_s << "\n";

	return true;
}```