server: split server.cpp code into server/common/task/queue (#17362)

* add server-task, server-common

* add server-queue

* rm redundant includes

* move enum stop_type to server-task

* server : headers cleanup

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

tools/server/server-queue.h

@@ -0,0 +1,110 @@
+#pragma once
+
+#include "server-task.h"
+
+#include <condition_variable>
+#include <deque>
+#include <mutex>
+#include <unordered_set>
+
+struct server_queue {
+private:
+    int id = 0;
+    bool running;
+
+    // queues
+    std::deque<server_task> queue_tasks;
+    std::deque<server_task> queue_tasks_deferred;
+
+    std::mutex mutex_tasks;
+    std::condition_variable condition_tasks;
+
+    // callback functions
+    std::function<void(server_task &&)> callback_new_task;
+    std::function<void(void)>           callback_update_slots;
+
+public:
+    // Add a new task to the end of the queue
+    int post(server_task && task, bool front = false);
+
+    // multi-task version of post()
+    int post(std::vector<server_task> && tasks, bool front = false);
+
+    // Add a new task, but defer until one slot is available
+    void defer(server_task && task);
+
+    // Get the next id for creating a new task
+    int get_new_id();
+
+    // Register function to process a new task
+    void on_new_task(std::function<void(server_task &&)> callback);
+
+    // Register the function to be called when all slots data is ready to be processed
+    void on_update_slots(std::function<void(void)> callback);
+
+    // Call when the state of one slot is changed, it will move one task from deferred to main queue
+    void pop_deferred_task();
+
+    // end the start_loop routine
+    void terminate();
+
+    /**
+     * Main loop consists of these steps:
+     * - Wait until a new task arrives
+     * - Process the task (i.e. maybe copy data into slot)
+     * - Check if multitask is finished
+     * - Update all slots
+     */
+    void start_loop();
+
+    // for metrics
+    size_t queue_tasks_deferred_size() {
+        std::unique_lock<std::mutex> lock(mutex_tasks);
+        return queue_tasks_deferred.size();
+    }
+
+private:
+    void cleanup_pending_task(int id_target);
+};
+
+struct server_response {
+private:
+    bool running = true;
+
+    // for keeping track of all tasks waiting for the result
+    std::unordered_set<int> waiting_task_ids;
+
+    // the main result queue (using ptr for polymorphism)
+    std::vector<server_task_result_ptr> queue_results;
+
+    std::mutex mutex_results;
+    std::condition_variable condition_results;
+
+public:
+    // add the id_task to the list of tasks waiting for response
+    void add_waiting_task_id(int id_task);
+
+    void add_waiting_tasks(const std::vector<server_task> & tasks);
+
+    // when the request is finished, we can remove task associated with it
+    void remove_waiting_task_id(int id_task);
+
+    // remove multiple tasks from waiting list
+    void remove_waiting_task_ids(const std::unordered_set<int> & id_tasks);
+
+    // This function blocks the thread until there is a response for one of the id_tasks
+    server_task_result_ptr recv(const std::unordered_set<int> & id_tasks);
+
+    // same as recv(), but have timeout in seconds
+    // if timeout is reached, nullptr is returned
+    server_task_result_ptr recv_with_timeout(const std::unordered_set<int> & id_tasks, int timeout);
+
+    // single-task version of recv()
+    server_task_result_ptr recv(int id_task);
+
+    // Send a new result to a waiting id_task
+    void send(server_task_result_ptr && result);
+
+    // terminate the waiting loop
+    void terminate();
+};