backend/llama.cpp/tools/server/server-queue.cpp

#include "server-task.h"
#include "server-queue.h"

#include "log.h"

#include <chrono>

#define QUE_INF(fmt, ...) LOG_INF("que  %12.*s: " fmt, 12, __func__, __VA_ARGS__)
#define QUE_WRN(fmt, ...) LOG_WRN("que  %12.*s: " fmt, 12, __func__, __VA_ARGS__)
#define QUE_ERR(fmt, ...) LOG_ERR("que  %12.*s: " fmt, 12, __func__, __VA_ARGS__)
#define QUE_DBG(fmt, ...) LOG_DBG("que  %12.*s: " fmt, 12, __func__, __VA_ARGS__)

#define RES_INF(fmt, ...) LOG_INF("res  %12.*s: " fmt, 12, __func__, __VA_ARGS__)
#define RES_WRN(fmt, ...) LOG_WRN("res  %12.*s: " fmt, 12, __func__, __VA_ARGS__)
#define RES_ERR(fmt, ...) LOG_ERR("res  %12.*s: " fmt, 12, __func__, __VA_ARGS__)
#define RES_DBG(fmt, ...) LOG_DBG("res  %12.*s: " fmt, 12, __func__, __VA_ARGS__)

//
// server_queue
//

int server_queue::post(server_task && task, bool front) {
    std::unique_lock<std::mutex> lock(mutex_tasks);
    GGML_ASSERT(task.id != -1);
    // if this is cancel task make sure to clean up pending tasks
    if (task.type == SERVER_TASK_TYPE_CANCEL) {
        cleanup_pending_task(task.id_target);
    }
    const int task_id = task.id;
    QUE_DBG("new task, id = %d, front = %d\n", task_id, front);
    if (front) {
        queue_tasks.push_front(std::move(task));
    } else {
        queue_tasks.push_back(std::move(task));
    }
    time_last_task = ggml_time_ms();
    condition_tasks.notify_one();
    return task_id;
}

int server_queue::post(std::vector<server_task> && tasks, bool front) {
    std::unique_lock<std::mutex> lock(mutex_tasks);
    for (auto & task : tasks) {
        if (task.id == -1) {
            task.id = id++;
        }
        // if this is cancel task make sure to clean up pending tasks
        if (task.type == SERVER_TASK_TYPE_CANCEL) {
            cleanup_pending_task(task.id_target);
        }
        QUE_DBG("new task, id = %d/%d, front = %d\n", task.id, (int) tasks.size(), front);
        if (front) {
            queue_tasks.push_front(std::move(task));
        } else {
            queue_tasks.push_back(std::move(task));
        }
    }
    time_last_task = ggml_time_ms();
    condition_tasks.notify_one();
    return 0;
}

void server_queue::defer(server_task && task) {
    std::unique_lock<std::mutex> lock(mutex_tasks);
    QUE_DBG("defer task, id = %d\n", task.id);
    queue_tasks_deferred.push_back(std::move(task));
    time_last_task = ggml_time_ms();
    condition_tasks.notify_one();
}

int server_queue::get_new_id() {
    std::unique_lock<std::mutex> lock(mutex_tasks);
    int new_id = id++;
    return new_id;
}

void server_queue::pop_deferred_task(int id_slot) {
    std::unique_lock<std::mutex> lock(mutex_tasks);
    if (!queue_tasks_deferred.empty()) {
        // try to find a task that uses the specified slot
        bool found = false;
        for (auto it = queue_tasks_deferred.begin(); it != queue_tasks_deferred.end(); ++it) {
            if (it->id_slot == id_slot) {
                QUE_DBG("pop deferred task (use slot %d), id_task = %d\n", id_slot, it->id);
                queue_tasks.emplace_front(std::move(*it));
                queue_tasks_deferred.erase(it);
                found = true;
                break;
            }
        }
        // if not tasks found using the slot, just pop the first deferred task (default behavior)
        if (!found) {
            QUE_DBG("pop deferred task, id_task = %d\n", queue_tasks_deferred.front().id);
            queue_tasks.emplace_front(std::move(queue_tasks_deferred.front()));
            queue_tasks_deferred.pop_front();
        }
    }
    time_last_task = ggml_time_ms();
    condition_tasks.notify_one();
}

void server_queue::wait_until_no_sleep() {
    std::unique_lock<std::mutex> lock(mutex_tasks);
    if (!sleeping) {
        return;
    } else {
        if (!req_stop_sleeping) {
            QUE_DBG("%s", "requesting to stop sleeping\n");
            req_stop_sleeping = true;
            condition_tasks.notify_one(); // only main thread is waiting on this
        }
        QUE_DBG("%s", "waiting until no sleep\n");
        condition_tasks.wait(lock, [&]{
            return !sleeping;
        });
    }
}

void server_queue::terminate() {
    std::unique_lock<std::mutex> lock(mutex_tasks);
    running = false;
    condition_tasks.notify_all();
}

void server_queue::start_loop(int64_t idle_sleep_ms) {
    running = true;
    time_last_task = ggml_time_ms();

    constexpr auto max_wait_time = std::chrono::seconds(1);
    auto should_sleep = [&]() -> bool {
        // caller must hold mutex_tasks
        if (idle_sleep_ms < 0) {
            return false;
        }
        int64_t now = ggml_time_ms();
        return (now - time_last_task) >= idle_sleep_ms;
    };

    while (true) {
        QUE_DBG("%s", "processing new tasks\n");

        while (true) {
            std::unique_lock<std::mutex> lock(mutex_tasks);
            if (!running) {
                QUE_DBG("%s", "terminate\n");
                return;
            }
            if (queue_tasks.empty()) {
                lock.unlock();
                break;
            }
            server_task task = std::move(queue_tasks.front());
            queue_tasks.pop_front();
            lock.unlock();

            QUE_DBG("processing task, id = %d\n", task.id);
            callback_new_task(std::move(task));
        }
        // all tasks in the current loop is processed, slots data is now ready
        QUE_DBG("%s", "update slots\n");

        // this will run the main inference process for all slots
        callback_update_slots();
        {
            // update_slots() may take a while to finish, we need to make sure it's not counted as idle
            std::unique_lock<std::mutex> lock(mutex_tasks);
            time_last_task = ggml_time_ms();
        }

        QUE_DBG("%s", "waiting for new tasks\n");
        while (true) {
            std::unique_lock<std::mutex> lock(mutex_tasks);
            if (!running || !queue_tasks.empty()) {
                break; // go back to process new tasks or terminate
            }

            // no tasks, check for sleeping state
            if (should_sleep()) {
                QUE_INF("%s", "entering sleeping state\n");
                sleeping = true;
                callback_sleeping_state(true);
                req_stop_sleeping = false;
                // wait until we are requested to exit sleeping state
                condition_tasks.wait(lock, [&]{
                    return (!running || req_stop_sleeping);
                });
                if (!running) { // may changed during sleep
                    break; // terminate
                }
                QUE_INF("%s", "exiting sleeping state\n");
                req_stop_sleeping = false;
                callback_sleeping_state(false);
                sleeping = false;
                time_last_task = ggml_time_ms();
                condition_tasks.notify_all(); // notify wait_until_no_sleep()
                break; // process new tasks
            } else {
                // wait for new tasks or timeout for checking sleeping condition
                bool res = condition_tasks.wait_for(lock, max_wait_time, [&]{
                    return (!queue_tasks.empty() || !running);
                });
                if (res) {
                    break; // new task arrived or terminate
                }
                // otherwise, loop again to check sleeping condition
            }
        }
    }
}

void server_queue::cleanup_pending_task(int id_target) {
    // no need lock because this is called exclusively by post()
    auto rm_func = [id_target](const server_task & task) {
        return task.id == id_target;
    };
    queue_tasks.erase(
        std::remove_if(queue_tasks.begin(),          queue_tasks.end(),          rm_func),
        queue_tasks.end());
    queue_tasks_deferred.erase(
        std::remove_if(queue_tasks_deferred.begin(), queue_tasks_deferred.end(), rm_func),
        queue_tasks_deferred.end());
}

//
// server_response
//

void server_response::add_waiting_task_id(int id_task) {
    RES_DBG("add task %d to waiting list. current waiting = %d (before add)\n", id_task, (int) waiting_task_ids.size());

    std::unique_lock<std::mutex> lock(mutex_results);
    waiting_task_ids.insert(id_task);
}

void server_response::add_waiting_task_ids(const std::unordered_set<int> & id_tasks) {
    std::unique_lock<std::mutex> lock(mutex_results);

    for (const auto & id_task : id_tasks) {
        RES_DBG("add task %d to waiting list. current waiting = %d (before add)\n", id_task, (int) waiting_task_ids.size());
        waiting_task_ids.insert(id_task);
    }
}

void server_response::remove_waiting_task_id(int id_task) {
    RES_DBG("remove task %d from waiting list. current waiting = %d (before remove)\n", id_task, (int) waiting_task_ids.size());

    std::unique_lock<std::mutex> lock(mutex_results);
    waiting_task_ids.erase(id_task);
    // make sure to clean up all pending results
    queue_results.erase(
        std::remove_if(queue_results.begin(), queue_results.end(), [id_task](const server_task_result_ptr & res) {
            return res->id == id_task;
        }),
        queue_results.end());
}

void server_response::remove_waiting_task_ids(const std::unordered_set<int> & id_tasks) {
    std::unique_lock<std::mutex> lock(mutex_results);

    for (const auto & id_task : id_tasks) {
        RES_DBG("remove task %d from waiting list. current waiting = %d (before remove)\n", id_task, (int) waiting_task_ids.size());
        waiting_task_ids.erase(id_task);
    }
}

server_task_result_ptr server_response::recv(const std::unordered_set<int> & id_tasks) {
    while (true) {
        std::unique_lock<std::mutex> lock(mutex_results);
        condition_results.wait(lock, [&]{
            if (!running) {
                RES_DBG("%s : queue result stop\n", "recv");
                std::terminate(); // we cannot return here since the caller is HTTP code
            }
            return !queue_results.empty();
        });

        for (size_t i = 0; i < queue_results.size(); i++) {
            if (id_tasks.find(queue_results[i]->id) != id_tasks.end()) {
                server_task_result_ptr res = std::move(queue_results[i]);
                queue_results.erase(queue_results.begin() + i);
                return res;
            }
        }
    }

    // should never reach here
}

server_task_result_ptr server_response::recv_with_timeout(const std::unordered_set<int> & id_tasks, int timeout) {
    while (true) {
        std::unique_lock<std::mutex> lock(mutex_results);

        for (int i = 0; i < (int) queue_results.size(); i++) {
            if (id_tasks.find(queue_results[i]->id) != id_tasks.end()) {
                server_task_result_ptr res = std::move(queue_results[i]);
                queue_results.erase(queue_results.begin() + i);
                return res;
            }
        }

        std::cv_status cr_res = condition_results.wait_for(lock, std::chrono::seconds(timeout));
        if (!running) {
            RES_DBG("%s : queue result stop\n", __func__);
            std::terminate(); // we cannot return here since the caller is HTTP code
        }
        if (cr_res == std::cv_status::timeout) {
            return nullptr;
        }
    }

    // should never reach here
}

server_task_result_ptr server_response::recv(int id_task) {
    std::unordered_set<int> id_tasks = {id_task};
    return recv(id_tasks);
}

void server_response::send(server_task_result_ptr && result) {
    RES_DBG("sending result for task id = %d\n", result->id);

    std::unique_lock<std::mutex> lock(mutex_results);
    for (const auto & id_task : waiting_task_ids) {
        if (result->id == id_task) {
            RES_DBG("task id = %d pushed to result queue\n", result->id);

            queue_results.emplace_back(std::move(result));
            condition_results.notify_all();
            return;
        }
    }
}

void server_response::broadcast(server_task_result_ptr && result) {
    std::unique_lock<std::mutex> lock(mutex_results);
    for (const auto & id_task : waiting_task_ids) {
        RES_DBG("task id = %d pushed to result queue\n", id_task);
        server_task_result_ptr res_copy(result->clone());
        res_copy->id = id_task; // override id with target task id
        queue_results.emplace_back(std::move(res_copy));
    }
    condition_results.notify_all();
}

void server_response::terminate() {
    running = false;
    condition_results.notify_all();
}

//
// server_response_reader
//

void server_response_reader::post_task(server_task && task, bool front) {
    GGML_ASSERT(id_tasks.empty() && "post_task() can only be called once per reader");
    GGML_ASSERT(!task.is_parent() && "not supported, use post_tasks() instead");
    task.index = 0;
    id_tasks.insert(task.id);
    states.push_back(task.create_state());
    queue_results.add_waiting_task_id(task.id);
    queue_tasks.post(std::move(task), front);
}

void server_response_reader::post_tasks(std::vector<server_task> && tasks, bool front) {
    GGML_ASSERT(id_tasks.empty() && "post_tasks() can only be called once per reader");
    id_tasks = server_task::get_list_id(tasks);
    states.reserve(tasks.size());
    size_t index = 0;
    for (auto & task : tasks) {
        task.index = index++;
        states.push_back(task.create_state());
        // for child tasks
        for (auto & child_task : task.child_tasks) {
            child_task.index = index++;
            states.push_back(child_task.create_state());
        }
    }
    GGML_ASSERT(states.size() == id_tasks.size());
    queue_results.add_waiting_task_ids(id_tasks);
    queue_tasks.post(std::move(tasks), front);
}

bool server_response_reader::has_next() const {
    return !cancelled && received_count < id_tasks.size();
}

// return nullptr if should_stop() is true before receiving a result
// note: if one error is received, it will stop further processing and return error result
server_task_result_ptr server_response_reader::next(const std::function<bool()> & should_stop) {
    while (true) {
        server_task_result_ptr result = queue_results.recv_with_timeout(id_tasks, polling_interval_seconds);
        if (result == nullptr) {
            // timeout, check stop condition
            if (should_stop()) {
                return nullptr;
            }
        } else {
            if (result->is_error()) {
                stop(); // cancel remaining tasks
                SRV_DBG("%s", "received error result, stopping further processing\n");
                return result;
            }
            if (!states.empty()) {
                // update the generation state if needed
                const size_t idx = result->index;
                GGML_ASSERT(idx < states.size());
                result->update(states[idx]);
            }
            if (result->is_stop()) {
                received_count++;
            }
            return result;
        }
    }

    // should not reach here
}

server_response_reader::batch_response server_response_reader::wait_for_all(const std::function<bool()> & should_stop) {
    batch_response batch_res;
    batch_res.results.clear();
    batch_res.results.resize(id_tasks.size());
    while (has_next()) {
        auto res = next(should_stop);
        if (res == nullptr) {
            batch_res.is_terminated = true;
            return batch_res;
        }
        if (res->is_error()) {
            batch_res.error = std::move(res);
            return batch_res;
        }
        const size_t idx = res->index;
        GGML_ASSERT(idx < batch_res.results.size() && "index out of range");
        GGML_ASSERT(batch_res.results[idx] == nullptr && "duplicate result received");
        batch_res.results[idx] = std::move(res);
    }
    return batch_res;
}

void server_response_reader::stop() {
    queue_results.remove_waiting_task_ids(id_tasks);
    if (has_next() && !cancelled) {
        // if tasks is not finished yet, cancel them
        cancelled = true;
        std::vector<server_task> cancel_tasks;
        cancel_tasks.reserve(id_tasks.size());
        for (const auto & id_task : id_tasks) {
            SRV_WRN("cancel task, id_task = %d\n", id_task);
            server_task task(SERVER_TASK_TYPE_CANCEL);
            task.id_target = id_task;
            queue_results.remove_waiting_task_id(id_task);
            cancel_tasks.push_back(std::move(task));
        }
        // push to beginning of the queue, so it has highest priority
        queue_tasks.post(std::move(cancel_tasks), true);
    } else {
        SRV_DBG("%s", "all tasks already finished, no need to cancel\n");
    }
}