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ThreadPool.h

//
// ThreadPool.h
//
// $Id: //poco/1.4/Foundation/include/Poco/ThreadPool.h#1 $
//
// Library: Foundation
// Package: Threading
// Module:  ThreadPool
//
// Definition of the ThreadPool class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_ThreadPool_INCLUDED
#define Foundation_ThreadPool_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Thread.h"
#include "Poco/Mutex.h"
#include <vector>


namespace Poco {


class Runnable;
class PooledThread;


00056 class Foundation_API ThreadPool
      /// A thread pool always keeps a number of threads running, ready
      /// to accept work.
      /// Creating and starting a threads can impose a significant runtime
      /// overhead to an application. A thread pool helps to improve
      /// the performance of an application by reducing the number
      /// of threads that have to be created (and destroyed again).
      /// Threads in a thread pool are re-used once they become
      /// available again.
      /// The thread pool always keeps a minimum number of threads
      /// running. If the demans for threads increases, additional
      /// threads are created. Once the demand for threads sinks
      /// again, no-longer used threads are stopped and removed
      /// from the pool.
{
public:
      ThreadPool(int minCapacity = 2,
            int maxCapacity = 16,
            int idleTime = 60,
            int stackSize = POCO_THREAD_STACK_SIZE);
            /// Creates a thread pool with minCapacity threads.
            /// If required, up to maxCapacity threads are created
            /// a NoThreadAvailableException exception is thrown.
            /// If a thread is running idle for more than idleTime seconds,
            /// and more than minCapacity threads are running, the thread
            /// is killed. Threads are created with given stack size.

      ThreadPool(const std::string& name,
            int minCapacity = 2,
            int maxCapacity = 16,
            int idleTime = 60,
            int stackSize = POCO_THREAD_STACK_SIZE);
            /// Creates a thread pool with the given name and minCapacity threads.
            /// If required, up to maxCapacity threads are created
            /// a NoThreadAvailableException exception is thrown.
            /// If a thread is running idle for more than idleTime seconds,
            /// and more than minCapacity threads are running, the thread
            /// is killed. Threads are created with given stack size.

      ~ThreadPool();
            /// Currently running threads will remain active
            /// until they complete. 
      
      void addCapacity(int n);
            /// Increases (or decreases, if n is negative)
            /// the maximum number of threads.

      int capacity() const;
            /// Returns the maximum capacity of threads.

      void setStackSize(int stackSize);
            /// Sets the stack size for threads.
            /// New stack size applies only for newly created threads.

      int getStackSize() const;
            /// Returns the stack size used to create new threads.

      int used() const;
            /// Returns the number of currently used threads.

      int allocated() const;
            /// Returns the number of currently allocated threads.

      int available() const;
            /// Returns the number available threads.

      void start(Runnable& target);
            /// Obtains a thread and starts the target.
            /// Throws a NoThreadAvailableException if no more
            /// threads are available.

      void start(Runnable& target, const std::string& name);
            /// Obtains a thread and starts the target.
            /// Assigns the given name to the thread.
            /// Throws a NoThreadAvailableException if no more
            /// threads are available.

      void startWithPriority(Thread::Priority priority, Runnable& target);
            /// Obtains a thread, adjusts the thread's priority, and starts the target.
            /// Throws a NoThreadAvailableException if no more
            /// threads are available.

      void startWithPriority(Thread::Priority priority, Runnable& target, const std::string& name);
            /// Obtains a thread, adjusts the thread's priority, and starts the target.
            /// Assigns the given name to the thread.
            /// Throws a NoThreadAvailableException if no more
            /// threads are available.

      void stopAll();
            /// Stops all running threads and waits for their completion.
            ///
            /// Will also delete all thread objects.
            /// If used, this method should be the last action before
            /// the thread pool is deleted.
            ///
            /// Note: If a thread fails to stop within 10 seconds 
            /// (due to a programming error, for example), the
            /// underlying thread object will not be deleted and
            /// this method will return anyway. This allows for a
            /// more or less graceful shutdown in case of a misbehaving
            /// thread.

      void joinAll();
            /// Waits for all threads to complete.
            ///
            /// Note that this will not actually join() the underlying
            /// thread, but rather wait for the thread's runnables
            /// to finish.

      void collect();
            /// Stops and removes no longer used threads from the
            /// thread pool. Can be called at various times in an
            /// application's life time to help the thread pool
            /// manage its threads. Calling this method is optional,
            /// as the thread pool is also implicitly managed in
            /// calls to start(), addCapacity() and joinAll().

      const std::string& name() const;
            /// Returns the name of the thread pool,
            /// or an empty string if no name has been
            /// specified in the constructor.

      static ThreadPool& defaultPool();
            /// Returns a reference to the default
            /// thread pool.

protected:
      PooledThread* getThread();
      PooledThread* createThread();

      void housekeep();

private:
      ThreadPool(const ThreadPool& pool);
      ThreadPool& operator = (const ThreadPool& pool);

      typedef std::vector<PooledThread*> ThreadVec;

      std::string _name;
      int _minCapacity;
      int _maxCapacity;
      int _idleTime;
      int _serial;
      int _age;
      int _stackSize;
      ThreadVec _threads;
      mutable FastMutex _mutex;
};


//
// inlines
//
00209 inline void ThreadPool::setStackSize(int stackSize)
{
      _stackSize = stackSize;
}


00215 inline int ThreadPool::getStackSize() const
{
      return _stackSize;
}


00221 inline const std::string& ThreadPool::name() const
{
      return _name;
}


} // namespace Poco


#endif // Foundation_ThreadPool_INCLUDED

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