In C++, RAII is typically used to coordinate initialization and cleanup. In asyncronous programming, RAII is not available, but for the control plane it is useful to bring up a seastar::thread to make use of it.
In conjunction with seastar::app_template, initialization and cleanup look like so:
#include <seastar/core/app-template.hh>
#include <seastar/core/reactor.hh>
#include <iostream>
int main(int argc, char** argv) {
seastar::app_template app;
return app.run(argc, argv, [] {
return seastar::async() {
std::cout << "Hello world\n";
my_class my_object;
// ... more code
// my_object will be destroyed here
return 0;
});
}If one needs to invoke an asynchronous function during shutdown, one can make use of the seastar::defer() function to schedule an arbitrary cleanup function:
#include <seastar/core/app-template.hh>
#include <seastar/core/reactor.hh>
#include <iostream>
int main(int argc, char** argv) {
seastar::app_template app;
return app.run(argc, argv, [] {
return seastar::async() {
std::cout << "Hello world\n";
my_class my_object;
// ... more code
auto cleanup = defer([] () noexcept {
// .get() joins the asynchronous function back
// into the thread.
call_async_cleanup_function().get();
});
// `cleanup` will invoke its function here, if we reached
// its construction point
// my_object will be destroyed here
return 0;
});
}See also seastar::deferred_close and seastar::deferred_stop for more ways to control cleanup.