cpp-httplib v0.61.0
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 handlers that are already running are allowed to finish. A response still being sent by a content provider (a streaming response, for example) is cut short, though. 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