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。所以就基于ACE寫了個，只做了初步測試。
主要思想是：
1. 重載ACE_Task，這相當于是個固定線程池，用一個信號量（ACE_Thread_Semaphore）來記數空閑線程數。
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，并且無空閑線程（信號量用光），判斷總線程數小于maxnum，就開始強迫增加線程數。
3. 當線程響應完一個請求（任務）后，如果當前任務隊列為空，且線程數大于minnum，就退出本線程。這里做了一個優化，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，之后，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。由于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"
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_pool.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) {
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;
}
#ifdef THREAD_POOL_UNIT_TEST
int main (int argc, int ** argv) {
printf ("begin test:\n");
/**//*
ACE_Thread_Semaphore* s = new ACE_Thread_Semaphore (0);
s->release (3);
s->acquire ();
s->acquire ();
s->acquire ();
printf ("ok");
return 0;
*/
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)
sleep (1);
}
sleep (1000);
printf ("end test:\n");
return 0;
}
#endif
posted on 2007-08-14 17:56
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