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AsyncRequest.cpp
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#include <deque>
#include <vector>
#include <string>
#include <sstream>
#include <cassert>
#include <thread>
#include <mutex>
#include <atomic>
#include <iostream>
#include <condition_variable>
#include <chrono>
#include "AsyncRequest.hpp"
#define ARESULT_CASE(arc) case arc : out << #arc; break
std::ostream& operator<<(std::ostream& out, AResult n) {
switch (n) {
ARESULT_CASE(AResult::Success);
ARESULT_CASE(AResult::Empty);
ARESULT_CASE(AResult::Full);
ARESULT_CASE(AResult::Pending);
ARESULT_CASE(AResult::Ready);
ARESULT_CASE(AResult::Stopped);
ARESULT_CASE(AResult::Timeout);
}
return out;
}
#undef ARESULT_CASE
//----------------------------------------------------------
typedef std::unique_lock<std::mutex> LockType;
// A queue that is aware of AsyncRequest and threads
//
class RequestQueue
{
public:
explicit RequestQueue(uint64_t qsize)
:
stopped(false),
max_queue_size(qsize)
{
}
// flag the queue as stopped and nothing enters
//
void shutdown();
void wait_for_empty();
// En/De queue
//
AResult enqueue(AsyncRequest* t, int timeout = AR_TIMEOUT_INFINITE);
AResult dequeue(AsyncRequest*& t, int timeout = AR_TIMEOUT_INFINITE);
AResult try_dequeue(AsyncRequest*& t) { return dequeue(t, 0); }
AResult try_enqueue(AsyncRequest* t) { return enqueue(t, 0); }
AResult try_dequeue_all(std::deque<AsyncRequest*>& result);
// condition variables operations
//
void notify_has_tasks() { tasks_ready.notify_one(); }
void notify_all() { tasks_ready.notify_all(); }
void notify_can_push() { can_push.notify_one(); }
bool wait_for_tasks(LockType& lock, int timeout) {
if (timeout == AR_TIMEOUT_INFINITE) {
tasks_ready.wait(lock);
return true;
}
else {
auto r = tasks_ready.wait_for(lock, std::chrono::microseconds(timeout));
return (r == std::cv_status::no_timeout);
}
}
bool wait_can_push(LockType& lock, int timeout) {
if (timeout == AR_TIMEOUT_INFINITE) {
can_push.wait(lock);
return true;
}
else {
auto r = can_push.wait_for(lock, std::chrono::microseconds(timeout));
return (r == std::cv_status::no_timeout);
}
}
// lock and call _size()
//
size_t size() const;
private:
bool _empty() const { return tasks_.empty(); }
size_t _size() const { return tasks_.size(); }
// data members
//
std::deque<AsyncRequest*> tasks_;
mutable std::mutex mutex_;
std::condition_variable tasks_ready;
std::condition_variable can_push;
std::atomic<bool> stopped;
uint64_t max_queue_size;
};
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
AResult RequestQueue::enqueue(AsyncRequest* t, int timeout)
{
LockType lock(mutex_);
if (_size() >= max_queue_size) {
// return immediatley in non-blocking mode
//
if (timeout == 0) {
lock.unlock();
return AResult::Full;
}
// otherwise block until waken up when a slot is available
//
if (!wait_can_push(lock, timeout)) {
lock.unlock();
return AResult::Timeout;
}
}
tasks_.push_back(t);
lock.unlock();
// wake up a sleeping thread (if any) to consume the new arrival
//
notify_has_tasks();
return AResult::Success;
}
//----------------------------------------------------------------------------
AResult RequestQueue::dequeue(AsyncRequest*& t, int timeout)
{
LockType lock(mutex_);
for (;;) {
if (!_empty()) {
t = tasks_.front();
tasks_.pop_front();
lock.unlock();
notify_can_push();
return AResult::Success;
}
// changed in a different thread!
//
if (this->stopped) {
lock.unlock();
t = nullptr;
return AResult::Stopped;
}
// If we are not in blocking mode, return immediately
//
if (timeout == 0) {
lock.unlock();
t = nullptr;
return AResult::Empty;
}
// Otherwise block until waken up by new arrivals or timeout
//
if (!wait_for_tasks(lock, timeout)) {
lock.unlock();
t = nullptr;
return AResult::Timeout;
}
}
}
//----------------------------------------------------------------------------
AResult RequestQueue::try_dequeue_all(std::deque<AsyncRequest*>& result)
{
LockType lock(mutex_);
std::deque<AsyncRequest*> tmp;
std::swap(tasks_, tmp);
lock.unlock();
notify_can_push();
if (tmp.empty())
return AResult::Empty;
std::swap(tmp, result);
return AResult::Success;
}
//----------------------------------------------------------------------------
void RequestQueue::shutdown()
{
// stopped is checked from a different thread. must lock!
//
LockType lock(mutex_);
stopped = true;
}
//----------------------------------------------------------------------------
void RequestQueue::wait_for_empty()
{
while (!_empty())
notify_has_tasks();
}
//----------------------------------------------------------------------------
size_t RequestQueue::size() const
{
// size is called from a different thread. must lock!
//
LockType lock(mutex_);
size_t result = _size();
lock.unlock();
return result;
}
//----------------------------------------------------------------------------
//---------------------------------
//
// AsyncRequestMgr Implementation
//
//---------------------------------
//
struct AsyncReqMgr_Imp
{
AsyncReqMgr_Imp(size_t nthreads_, uint64_t qsize)
:
nthreads(nthreads_),
submission_queue(qsize),
completion_queue(qsize),
stopped(true),
n_submitted(0)
{
}
// data
//
size_t nthreads;
RequestQueue submission_queue;
RequestQueue completion_queue;
std::atomic<bool> stopped;
std::atomic<unsigned long> n_submitted;
std::vector<std::thread> workers;
std::mutex log_mutex;
std::vector<std::string> log_messages;
};
typedef std::unique_ptr<AsyncReqMgr_Imp> UPimp;
//----------------------------------------------------------------------------
// the constructor just launches some amount of workers
//
AsyncRequestMgr::AsyncRequestMgr(size_t nthreads_, uint64_t qsize)
:
pImp(std::make_unique<AsyncReqMgr_Imp>(nthreads_, qsize))
{
}
//-----------------------------------------------------------------------
// the destructor joins all threads (if not already)
//
AsyncRequestMgr::~AsyncRequestMgr()
{
this->shutdown();
}
//-----------------------------------------------------------------------
void AsyncRequestMgr::shutdown()
{
if (pImp->stopped)
return;
// stop all threads
//
pImp->submission_queue.shutdown();
pImp->submission_queue.wait_for_empty();
pImp->submission_queue.notify_all();
// join them
//
for (std::thread& t : pImp->workers) {
t.join();
}
// destroy threads
//
pImp->workers.clear();
pImp->stopped = true;
}
//-----------------------------------------------------------------------
AResult AsyncRequestMgr::submit(AsyncRequest* t, int timeout)
{
if (pImp->stopped)
return AResult::Stopped;
auto res = pImp->submission_queue.enqueue(t, timeout);
if (res == AResult::Success)
++pImp->n_submitted;
return res;
}
//-----------------------------------------------------------------------
AResult AsyncRequestMgr::receive(AsyncRequest*& t, int timeout)
{
AResult rc;
if (pImp->n_submitted == 0) {
if (pImp->stopped)
rc = AResult::Stopped;
else
rc = AResult::Empty;
}
else {
rc = pImp->completion_queue.dequeue(t, timeout);
if (t)
--pImp->n_submitted;
}
return rc;
}
//-----------------------------------------------------------------------
static AResult poll_aux(UPimp& pImp, std::deque<AsyncRequest*>* presult)
{
AResult rc;
if (pImp->n_submitted == 0) {
if (pImp->stopped)
rc = AResult::Stopped;
else
rc = AResult::Empty;
}
else if (presult) {
pImp->completion_queue.try_dequeue_all(*presult);
if (size_t nready = presult->size()) {
pImp->n_submitted -= nready;
rc = AResult::Ready;
}
else
rc = AResult::Pending;
}
else if (pImp->completion_queue.size())
rc = AResult::Ready;
else
rc = AResult::Pending;
return rc;
}
//-----------------------------------------------------------------------
AResult AsyncRequestMgr::poll(std::deque<AsyncRequest*>& result)
{
return poll_aux(pImp, &result);
}
//-----------------------------------------------------------------------
AResult AsyncRequestMgr::poll() const
{
return poll_aux(pImp, nullptr);
}
//-----------------------------------------------------------------------
void AsyncRequestMgr::receive_log_messages(std::vector<std::string>& to)
{
LockType lock(pImp->log_mutex);
if (pImp->log_messages.empty())
return;
pImp->log_messages.swap(to);
}
//-----------------------------------------------------------------------
static void handle_thread_event(UPimp& pImp, const char* msg)
{
std::ostringstream out;
out << "Thread " << std::this_thread::get_id() << ": " << msg;
LockType lock(pImp->log_mutex);
pImp->log_messages.push_back(out.str());
}
//-----------------------------------------------------------------------
// Must not let exceptions propagate out of a thread function
//
static void task_call(UPimp& pImp, AsyncRequest* task)
{
try
{
task->call();
}
catch(std::exception& err)
{
handle_thread_event(pImp, err.what());
}
catch(...)
{
handle_thread_event(pImp, "Unkown exception caught!");
}
}
//-----------------------------------------------------------------------
void AsyncRequestMgr::worker_run()
{
// All threads in the pool are invoked with this function.
//
for (;;) {
AsyncRequest* task;
// Dequeue task from submission queue.
// exit thread if in stopped condition
//
if (pImp->submission_queue.dequeue(task) == AResult::Stopped) {
handle_thread_event(pImp, "normal stop");
return;
}
if (task) {
// execute the task
//
task_call(pImp, task);
// Put task in completion queue
//
pImp->completion_queue.enqueue(task);
}
}
}
//-----------------------------------------------------------------------
void AsyncRequestMgr::start()
{
if (pImp->stopped) {
// flag as active
//
pImp->stopped = false;
// start worker threads
//
for (size_t i = 0; i < pImp->nthreads; ++i)
pImp->workers.push_back(std::thread(&AsyncRequestMgr::worker_run, this));
}
}
//-----------------------------------------------------------------------