pipelining.h

/*
 * Copyright (c) 2008-2022, Hazelcast, Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#pragma once
 
#include <vector>
#include <mutex>
#include <condition_variable>
 
#include <boost/thread/future.hpp>
 
#include "hazelcast/util/Preconditions.h"
 
namespace hazelcast {
namespace client {
template<typename E>
class pipelining : public std::enable_shared_from_this<pipelining<E>>
{
public:
    static std::shared_ptr<pipelining> create(int depth)
    {
        util::Preconditions::check_positive(depth, "depth must be positive");
 
        return std::shared_ptr<pipelining>(new pipelining(depth));
    }
 
    std::vector<boost::optional<E>> results()
    {
        std::vector<boost::optional<E>> result;
        result.reserve(futures_.size());
        auto result_futures = when_all(futures_.begin(), futures_.end());
        for (auto& f : result_futures.get()) {
            result.emplace_back(f.get());
        }
        return result;
    }
 
    void add(boost::future<boost::optional<E>> future)
    {
        down();
 
        futures_.push_back(future.share());
    }
 
private:
    pipelining(int depth)
      : permits_(
          util::Preconditions::check_positive(depth, "depth must be positive"))
    {}
 
    void down()
    {
        int usedPermits = 0;
        for (auto& f : futures_) {
            if (!f.is_ready()) {
                ++usedPermits;
            }
        }
        if (usedPermits >= permits_) {
            decltype(futures_) outStandingFutures;
            for (auto& f : futures_) {
                if (!f.is_ready()) {
                    outStandingFutures.push_back(f);
                }
            }
 
            if (!outStandingFutures.empty()) {
                boost::when_any(outStandingFutures.begin(),
                                outStandingFutures.end())
                  .get();
            }
        }
    }
 
    int permits_;
    std::vector<boost::shared_future<boost::optional<E>>> futures_;
};
} // namespace client
} // namespace hazelcast