C++實現的帶最大最小線程數的線程池（基於ACE）

最近需要一個能根據請求數變化的線程池，JAVA有這樣的東西，可是C++下好像一般只是固定大小的線程池。所以就基於ACE寫了個，只做了初步測試。

主要思想是：

1. 重載ACE_Task，這相當於是個固定線程池，用一個信號量（ACE_Thread_Semaphore）來記數空閒線程數。

2. 初始化時根據用戶的輸入，確定最少線程數minnum和最大線程數maxnum，當多個請求到來，並且無空閒線程（信號量用光），判斷總線程數小於maxnum，就開始強迫增加線程數。

3. 當線程響應完一個請求（任務）後，如果當前任務隊列爲空，且線程數大於minnum，就退出本線程。這裏做了一個優化，就算滿足條件，線程也會在隊列上再等待10秒，防止線程池抖動帶來不必要的開銷。

使用：

重載這個類，重載service_func函數實現自己的任務處理。

start_pool初始化線程池，之後，就可以用add_task向線程池添加任務。

它會根據請求的數量自動控制池大小進行處理。

已經在LINUX下測試通過。由於ACE是跨平臺的，所以這個實現也應該可以在WINDOWS下工作。

編譯：

帶THREAD_POOL_UNIT_TEST選項，則編譯出自測程序test

gcc -g -Wall -O2 -g -Wall -I. -I../ -I../mon/comm/ACE_wrappers -g -DTHREAD_POOL_UNIT_TEST -o test thread_pool.cpp -lpthread -lm -lz -lstdc++ ../mon/comm/ACE_wrappers/ace/libACE.a -ldl

thread_pool.h頭文件：

#ifndef THREAD_POOL #define THREAD_POOL #include "ace/Task.h" #include "ace/Thread_Mutex.h" #include "ace/Thread_Semaphore.h" #include <ace/OS.h> class thread_pool : public ACE_Task<ACE_MT_SYNCH> { public: thread_pool (); ~thread_pool (); // begin the initial threads and waiting for request int start_pool ( int minnum = 5, // min number of thread int maxnum = 100, // max number of thread int waitsize = 1024, // request queue length int parsize = 1024); // your parameter size // pending request in work queue int wait_cnt (); // add one task to thread pool int add_task (void *arg, int size); // user defined work thread function virtual int service_func (void* arg); // overide base class function for thread pool logical virtual int svc (void); // not use virtual int handle_timeout (const ACE_Time_Value &tv, const void *arg); private: int minnum_, maxnum_; int waitsize_, parsize_; // ACE_Recursive_Thread_Mutex free_thread_cnt__mutex_; ACE_Thread_Semaphore *pfree_thread_; // for free thread count long thread_flags_; // ace thread create flag }; #endif /**//* THREAD_POOL */ thread_pool.cpp實現文件： #include "thread.h" #define THREAD_POOL_DONOT_ACQUIRE 0x1001 // do not aquire again in new added thread thread_pool::thread_pool () { thread_flags_ = THR_NEW_LWP | THR_JOINABLE | THR_INHERIT_SCHED; pfree_thread_ = NULL; } thread_pool::~thread_pool () { if (pfree_thread_) delete pfree_thread_; } int thread_pool::wait_cnt () { return this->msg_queue()->message_count (); } int thread_pool::handle_timeout (const ACE_Time_Value &tv, const void *arg) { return 0; } int thread_pool::start_pool ( int minnum, int maxnum, int waitsize, int parsize ) { minnum_ = minnum; maxnum_ = maxnum; waitsize_ = waitsize; parsize_ = parsize; this->msg_queue()->high_water_mark (waitsize * parsize); pfree_thread_ = new ACE_Thread_Semaphore (minnum); int ret = this->activate (thread_flags_, minnum); return ret; } int thread_pool::add_task (void *arg, int size) { ACE_Message_Block *mb = new ACE_Message_Block (parsize_); // test free threads condition if (pfree_thread_->tryacquire () == -1) { // acquire one free thread to do work printf ("free thread used up/n"); if (this->thr_count () < maxnum_) { this->activate (thread_flags_, 1, 1); printf ("new thread release/n"); pfree_thread_->release (); printf ("new one thread, now %d/n", this->thr_count ()); } else { printf ("can't new more threads, queue len %d/n", wait_cnt () + 1); } } else { // pfree_thread_->release (); // restore cnt, let svc function do acquire work printf ("new task acquire/n"); mb->set_flags (THREAD_POOL_DONOT_ACQUIRE); } // create msg printf ("add msg/n"); memcpy (mb->wr_ptr (), (char*) arg, size); this->putq (mb); return 0; } int thread_pool::service_func (void* arg) { ACE_OS::sleep (1); printf ("finished task %d in thread %02X/n", *(int*) arg, (int)ACE_Thread::self ()); return 0; } int thread_pool::svc (void) { printf ("thread started/n"); while (1) { ACE_Message_Block *b = 0; ACE_Time_Value wait = ACE_OS::gettimeofday (); wait.sec (wait.sec () + 10); // timeout in 10 secs to test if more tasks need to do or we'll exit if (this->getq (b, &wait) < 0) { if (this->thr_count () > minnum_) { printf ("over task acquire/n"); pfree_thread_->acquire (); printf ("delete one thread, now %d/n", this->thr_count ()-1); return 0; } else continue; // I'm the one of last min number of threads } if (b->flags () & THREAD_POOL_DONOT_ACQUIRE == 0) { printf ("queue task acquire/n"); pfree_thread_->acquire (); // I'll use one free thread } else printf ("no need to acquire/n"); this->service_func ((void*)b->rd_ptr()); printf ("finished release/n"); b->release(); pfree_thread_->release (); // added one free thread } return 0; } int main (int argc, char* argv[]) { printf ("begin test:/n"); thread_pool t; t.start_pool (10, 100); for (int i=0; i<200; i++) { t.add_task (&i, sizeof(i)); if (i % 20 == 0) ACE_OS::sleep (1); } ACE_OS::sleep (2); ACE_Thread_Manager::instance()->wait(); return 0; }