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apr_thread_pool.h
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/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed * with this work for additional information regarding copyright * ownership. The ASF licenses this file to you under the Apache * License, Version 2.0 (the "License"); you may not use this file * except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or * implied. See the License for the specific language governing * permissions and limitations under the License. */ #ifndef APU_THREAD_POOL_H #define APU_THREAD_POOL_H #include "apu.h" #include "apr_thread_proc.h" /** * @file apr_thread_pool.h * @brief APR Thread Pool Library * @remarks This library implements a thread pool using apr_thread_t. A thread * pool is a set of threads that can be created in advance or on demand until a * maximum number. When a task is scheduled, the thread pool will find an idle * thread to handle the task. In case all existing threads are busy and the * number of tasks in the queue is higher than the adjustable threshold, the * pool will try to create a new thread to serve the task if the maximum number * has not been reached. Otherwise, the task will be put into a queue based on * priority, which can be valued from 0 to 255, with higher values being served * first. If there are tasks with the same priority, the new task might be put at * the top or at the bottom - it depends on which function is used to put the task. * * @remarks There may be the case where the thread pool can use up to the maximum * number of threads at peak load, but having those threads idle afterwards. A * maximum number of idle threads can be set so that the extra idling threads will * be terminated to save system resources. */ #if APR_HAS_THREADS #ifdef __cplusplus extern "C" { #endif /* __cplusplus */ /** * @defgroup APR_Util_TP Thread Pool routines * @ingroup APR_Util * @{ */ /** Opaque Thread Pool structure. */ typedef struct apr_thread_pool apr_thread_pool_t; #define APR_THREAD_TASK_PRIORITY_LOWEST 0 #define APR_THREAD_TASK_PRIORITY_LOW 63 #define APR_THREAD_TASK_PRIORITY_NORMAL 127 #define APR_THREAD_TASK_PRIORITY_HIGH 191 #define APR_THREAD_TASK_PRIORITY_HIGHEST 255 /** * Create a thread pool * @param me The pointer in which to return the newly created apr_thread_pool * object, or NULL if thread pool creation fails. * @param init_threads The number of threads to be created initially, this number * will also be used as the initial value for the maximum number of idle threads. * @param max_threads The maximum number of threads that can be created * @param pool The pool to use * @return APR_SUCCESS if the thread pool was created successfully. Otherwise, * the error code. */ APU_DECLARE(apr_status_t) apr_thread_pool_create(apr_thread_pool_t **me, apr_size_t init_threads, apr_size_t max_threads, apr_pool_t *pool); /** * Destroy the thread pool and stop all the threads * @return APR_SUCCESS if all threads are stopped. */ APU_DECLARE(apr_status_t) apr_thread_pool_destroy(apr_thread_pool_t *me); /** * Schedule a task to the bottom of the tasks of same priority. * @param me The thread pool * @param func The task function * @param param The parameter for the task function * @param priority The priority of the task. * @param owner Owner of this task. * @return APR_SUCCESS if the task had been scheduled successfully */ APU_DECLARE(apr_status_t) apr_thread_pool_push(apr_thread_pool_t *me, apr_thread_start_t func, void *param, apr_byte_t priority, void *owner); /** * Schedule a task to be run after a delay * @param me The thread pool * @param func The task function * @param param The parameter for the task function * @param time Time in microseconds * @param owner Owner of this task. * @return APR_SUCCESS if the task had been scheduled successfully */ APU_DECLARE(apr_status_t) apr_thread_pool_schedule(apr_thread_pool_t *me, apr_thread_start_t func, void *param, apr_interval_time_t time, void *owner); /** * Schedule a task to the top of the tasks of same priority. * @param me The thread pool * @param func The task function * @param param The parameter for the task function * @param priority The priority of the task. * @param owner Owner of this task. * @return APR_SUCCESS if the task had been scheduled successfully */ APU_DECLARE(apr_status_t) apr_thread_pool_top(apr_thread_pool_t *me, apr_thread_start_t func, void *param, apr_byte_t priority, void *owner); /** * Cancel tasks submitted by the owner. If there is any task from the owner that * is currently running, the function will spin until the task finished. * @param me The thread pool * @param owner Owner of the task * @return APR_SUCCESS if the task has been cancelled successfully * @note The task function should not be calling cancel, otherwise the function * may get stuck forever. The function assert if it detect such a case. */ APU_DECLARE(apr_status_t) apr_thread_pool_tasks_cancel(apr_thread_pool_t *me, void *owner); /** * Get the current number of tasks waiting in the queue * @param me The thread pool * @return Number of tasks in the queue */ APU_DECLARE(apr_size_t) apr_thread_pool_tasks_count(apr_thread_pool_t *me); /** * Get the current number of scheduled tasks waiting in the queue * @param me The thread pool * @return Number of scheduled tasks in the queue */ APU_DECLARE(apr_size_t) apr_thread_pool_scheduled_tasks_count(apr_thread_pool_t *me); /** * Get the current number of threads * @param me The thread pool * @return Total number of threads */ APU_DECLARE(apr_size_t) apr_thread_pool_threads_count(apr_thread_pool_t *me); /** * Get the current number of busy threads * @param me The thread pool * @return Number of busy threads */ APU_DECLARE(apr_size_t) apr_thread_pool_busy_count(apr_thread_pool_t *me); /** * Get the current number of idle threads * @param me The thread pool * @return Number of idle threads */ APU_DECLARE(apr_size_t) apr_thread_pool_idle_count(apr_thread_pool_t *me); /** * Access function for the maximum number of idle threads. Number of current * idle threads will be reduced to the new limit. * @param me The thread pool * @param cnt The number * @return The number of threads that were stopped. */ APU_DECLARE(apr_size_t) apr_thread_pool_idle_max_set(apr_thread_pool_t *me, apr_size_t cnt); /** * Get number of tasks that have run * @param me The thread pool * @return Number of tasks that have run */ APU_DECLARE(apr_size_t) apr_thread_pool_tasks_run_count(apr_thread_pool_t * me); /** * Get high water mark of the number of tasks waiting to run * @param me The thread pool * @return High water mark of tasks waiting to run */ APU_DECLARE(apr_size_t) apr_thread_pool_tasks_high_count(apr_thread_pool_t * me); /** * Get high water mark of the number of threads * @param me The thread pool * @return High water mark of threads in thread pool */ APU_DECLARE(apr_size_t) apr_thread_pool_threads_high_count(apr_thread_pool_t * me); /** * Get the number of idle threads that were destroyed after timing out * @param me The thread pool * @return Number of idle threads that timed out */ APU_DECLARE(apr_size_t) apr_thread_pool_threads_idle_timeout_count(apr_thread_pool_t * me); /** * Access function for the maximum number of idle threads * @param me The thread pool * @return The current maximum number */ APU_DECLARE(apr_size_t) apr_thread_pool_idle_max_get(apr_thread_pool_t *me); /** * Access function for the maximum number of threads. * @param me The thread pool * @param cnt Number of threads * @return The original maximum number of threads */ APU_DECLARE(apr_size_t) apr_thread_pool_thread_max_set(apr_thread_pool_t *me, apr_size_t cnt); /** * Access function for the maximum wait time (in microseconds) of an * idling thread that exceeds the maximum number of idling threads. * A non-zero value allows for the reaping of idling threads to shrink * over time. Which helps reduce thrashing. * @param me The thread pool * @param timeout The number of microseconds an idle thread should wait * till it reaps itself * @return The original maximum wait time */ APU_DECLARE(apr_interval_time_t) apr_thread_pool_idle_wait_set(apr_thread_pool_t * me, apr_interval_time_t timeout); /** * Access function for the maximum wait time (in microseconds) of an * idling thread that exceeds the maximum number of idling threads * @param me The thread pool * @return The current maximum wait time */ APU_DECLARE(apr_interval_time_t) apr_thread_pool_idle_wait_get(apr_thread_pool_t * me); /** * Access function for the maximum number of threads * @param me The thread pool * @return The current maximum number */ APU_DECLARE(apr_size_t) apr_thread_pool_thread_max_get(apr_thread_pool_t *me); /** * Access function for the threshold of tasks in queue to trigger a new thread. * @param me The thread pool * @param cnt The new threshold * @return The original threshold */ APU_DECLARE(apr_size_t) apr_thread_pool_threshold_set(apr_thread_pool_t *me, apr_size_t val); /** * Access function for the threshold of tasks in queue to trigger a new thread. * @param me The thread pool * @return The current threshold */ APU_DECLARE(apr_size_t) apr_thread_pool_threshold_get(apr_thread_pool_t * me); /** * Get owner of the task currently been executed by the thread. * @param thd The thread is executing a task * @param owner Pointer to receive owner of the task. * @return APR_SUCCESS if the owner is retrieved successfully */ APU_DECLARE(apr_status_t) apr_thread_pool_task_owner_get(apr_thread_t *thd, void **owner); /** @} */ #ifdef __cplusplus } #endif #endif /* APR_HAS_THREADS */ #endif /* !APR_THREAD_POOL_H */