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database/apache/include/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 */