server : graceful server shutdown (#5244)

This updates the server queue to support graceful shutdown of the server on signals.

examples/server/server.cpp

@@ -28,6 +28,7 @@
 #include <chrono>
 #include <condition_variable>
 #include <atomic>
+#include <signal.h>
 
 using json = nlohmann::json;
 
@@ -2511,6 +2512,9 @@ static void append_to_generated_text_from_generated_token_probs(llama_server_con
     }
 }
 
+std::function<void(int)> shutdown_handler;
+inline void signal_handler(int signal) { shutdown_handler(signal); }
+
 int main(int argc, char **argv)
 {
 #if SERVER_VERBOSE != 1
@@ -3128,8 +3132,25 @@ int main(int argc, char **argv)
         std::placeholders::_2,
         std::placeholders::_3
     ));
-    llama.queue_tasks.start_loop();
 
+    shutdown_handler = [&](int) {
+        llama.queue_tasks.terminate();
+    };
+
+#if defined (__unix__) || (defined (__APPLE__) && defined (__MACH__))
+    struct sigaction sigint_action;
+    sigint_action.sa_handler = signal_handler;
+    sigemptyset (&sigint_action.sa_mask);
+    sigint_action.sa_flags = 0;
+    sigaction(SIGINT, &sigint_action, NULL);
+#elif defined (_WIN32)
+    auto console_ctrl_handler = +[](DWORD ctrl_type) -> BOOL {
+        return (ctrl_type == CTRL_C_EVENT) ? (signal_handler(SIGINT), true) : false;
+    };
+    SetConsoleCtrlHandler(reinterpret_cast<PHANDLER_ROUTINE>(console_ctrl_handler), true);
+#endif
+    llama.queue_tasks.start_loop();
+    svr.stop();
     t.join();
 
     llama_backend_free();

examples/server/utils.hpp

@@ -220,6 +220,7 @@ inline std::string format_chatml(std::vector<json> messages)
 struct llama_server_queue {
     int id = 0;
     std::mutex mutex_tasks;
+    bool running;
     // queues
     std::vector<task_server> queue_tasks;
     std::vector<task_server> queue_tasks_deferred;
@@ -278,9 +279,18 @@ struct llama_server_queue {
         queue_tasks_deferred.clear();
     }
 
-    // Start the main loop. This call is blocking
-    [[noreturn]]
+    // end the start_loop routine
+    void terminate() {
+        {
+            std::unique_lock<std::mutex> lock(mutex_tasks);
+            running = false;
+        }
+        condition_tasks.notify_all();
+    }
+
+    // Start the main loop.
     void start_loop() {
+        running = true;
         while (true) {
             // new task arrived
             LOG_VERBOSE("have new task", {});
@@ -324,8 +334,12 @@ struct llama_server_queue {
             {
                 std::unique_lock<std::mutex> lock(mutex_tasks);
                 if (queue_tasks.empty()) {
+                    if (!running) {
+                        LOG_VERBOSE("ending start_loop", {});
+                        return;
+                    }
                     condition_tasks.wait(lock, [&]{
-                        return !queue_tasks.empty();
+                        return (!queue_tasks.empty() || !running);
                     });
                 }
             }