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/**
* @file threadpool.h
* @author Nat Goodspeed
* @date 2021-10-21
* @brief ThreadPool configures a WorkQueue along with a pool of threads to
* service it.
*
* $LicenseInfo:firstyear=2021&license=viewerlgpl$
* Copyright (c) 2021, Linden Research, Inc.
* $/LicenseInfo$
*/
#if ! defined(LL_THREADPOOL_H)
#define LL_THREADPOOL_H
#include "threadpool_fwd.h"
#include "workqueue.h"
#include <memory> // std::unique_ptr
#include <string>
#include <thread>
#include <utility> // std::pair
#include <vector>
namespace LL
{
class ThreadPoolBase: public LLInstanceTracker<ThreadPoolBase, std::string>
{
private:
using super = LLInstanceTracker<ThreadPoolBase, std::string>;
public:
/**
* Pass ThreadPoolBase a string name. This can be used to look up the
* relevant WorkQueue.
*
* The number of threads you pass sets the compile-time default. But
* if the user has overridden the LLSD map in the "ThreadPoolSizes"
* setting with a key matching this ThreadPool name, that setting
* overrides this parameter.
*/
ThreadPoolBase(const std::string& name, size_t threads,
WorkQueueBase* queue);
virtual ~ThreadPoolBase();
/**
* Launch the ThreadPool. Until this call, a constructed ThreadPool
* launches no threads. That permits coders to derive from ThreadPool,
* or store it as a member of some other class, but refrain from
* launching it until all other construction is complete.
*/
void start();
/**
* ThreadPool listens for application shutdown messages on the "LLApp"
* LLEventPump. Call close() to shut down this ThreadPool early.
*/
void close();
std::string getName() const { return mName; }
size_t getWidth() const { return mThreads.size(); }
/**
* Override run() if you need special processing. The default run()
* implementation simply calls WorkQueue::runUntilClose().
*/
virtual void run();
/**
* getConfiguredWidth() returns the setting, if any, for the specified
* ThreadPool name. Returns dft if the "ThreadPoolSizes" map does not
* contain the specified name.
*/
static
size_t getConfiguredWidth(const std::string& name, size_t dft=0);
/**
* This getWidth() returns the width of the instantiated ThreadPool
* with the specified name, if any. If no instance exists, returns its
* getConfiguredWidth() if any. If there's no instance and no relevant
* override, return dft. Presumably dft should match the threads
* parameter passed to the ThreadPool constructor call that will
* eventually instantiate the ThreadPool with that name.
*/
static
size_t getWidth(const std::string& name, size_t dft);
protected:
std::unique_ptr<WorkQueueBase> mQueue;
private:
void run(const std::string& name);
std::string mName;
size_t mThreadCount;
std::vector<std::pair<std::string, std::thread>> mThreads;
};
/**
* Specialize with WorkQueue or, for timestamped tasks, WorkSchedule
*/
template <class QUEUE>
struct ThreadPoolUsing: public ThreadPoolBase
{
using queue_t = QUEUE;
/**
* Pass ThreadPoolUsing a string name. This can be used to look up the
* relevant WorkQueue.
*
* The number of threads you pass sets the compile-time default. But
* if the user has overridden the LLSD map in the "ThreadPoolSizes"
* setting with a key matching this ThreadPool name, that setting
* overrides this parameter.
*
* Pass an explicit capacity to limit the size of the queue.
* Constraining the queue can cause a submitter to block. Do not
* constrain any ThreadPool accepting work from the main thread.
*/
ThreadPoolUsing(const std::string& name, size_t threads=1, size_t capacity=1024*1024):
ThreadPoolBase(name, threads, new queue_t(name, capacity))
{}
~ThreadPoolUsing() override {}
/**
* obtain a non-const reference to the specific WorkQueue subclass to
* post work to it
*/
queue_t& getQueue() { return static_cast<queue_t&>(*mQueue); }
};
/// ThreadPool is shorthand for using the simpler WorkQueue
using ThreadPool = ThreadPoolUsing<WorkQueue>;
} // namespace LL
#endif /* ! defined(LL_THREADPOOL_H) */
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