cpp-httplib v0.42.0
DRAFT

S19. Shut Down Gracefully

To stop the server, call Server::stop(). It's safe to call even while requests are in flight, so you can wire it to SIGINT or SIGTERM for a graceful shutdown.

Basic usage

httplib::Server svr;

svr.Get("/", [](const auto &, auto &res) { res.set_content("ok", "text/plain"); });

std::thread t([&] { svr.listen("0.0.0.0", 8080); });

// wait for input on the main thread, or whatever
std::cin.get();

svr.stop();
t.join();

httplib::Server svr;

svr.Get("/", [](const auto &, auto &res) { res.set_content("ok", "text/plain"); });

std::thread t([&] { svr.listen("0.0.0.0", 8080); });

// wait for input on the main thread, or whatever
std::cin.get();

svr.stop();
t.join();

listen() blocks, so the typical pattern is: run the server on a background thread and call stop() from the main thread. After stop(), listen() returns and you can join().

Shut down on a signal

Here's how to stop the server on SIGINT (Ctrl+C) or SIGTERM.

#include <csignal>

httplib::Server svr;

// global so the signal handler can reach it
httplib::Server *g_svr = nullptr;

int main() {
  svr.Get("/", [](const auto &, auto &res) { res.set_content("ok", "text/plain"); });

  g_svr = &svr;
  std::signal(SIGINT,  [](int) { if (g_svr) g_svr->stop(); });
  std::signal(SIGTERM, [](int) { if (g_svr) g_svr->stop(); });

  svr.listen("0.0.0.0", 8080);
  std::cout << "server stopped" << std::endl;
}

#include <csignal>

httplib::Server svr;

// global so the signal handler can reach it
httplib::Server *g_svr = nullptr;

int main() {
  svr.Get("/", [](const auto &, auto &res) { res.set_content("ok", "text/plain"); });

  g_svr = &svr;
  std::signal(SIGINT,  [](int) { if (g_svr) g_svr->stop(); });
  std::signal(SIGTERM, [](int) { if (g_svr) g_svr->stop(); });

  svr.listen("0.0.0.0", 8080);
  std::cout << "server stopped" << std::endl;
}

stop() is thread-safe and signal-safe — you can call it from a signal handler. Even when listen() is running on the main thread, the signal pulls it out cleanly.

What happens to in-flight requests

When you call stop(), new connections are refused, but requests already being processed are allowed to finish. Once all workers drain, listen() returns. That's what makes it graceful.

Warning: There's a wait between calling stop() and listen() returning — it's the time in-flight requests take to finish. To enforce a timeout, you'll need to add your own shutdown timer in application code.

ESC