rippled/src/ripple/app/misc/LoadFeeTrack.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012, 2013 Ripple Labs Inc.

    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================

#ifndef RIPPLE_CORE_LOADFEETRACK_H_INCLUDED
#define RIPPLE_CORE_LOADFEETRACK_H_INCLUDED

#include <ripple/json/json_value.h>
#include <ripple/beast/utility/Journal.h>
#include <algorithm>
#include <cstdint>
#include <mutex>

namespace ripple {

struct Fees;

/** Manages the current fee schedule.

    The "base" fee is the cost to send a reference transaction under no load,
    expressed in millionths of one XRP.

    The "load" fee is how much the local server currently charges to send a
    reference transaction. This fee fluctuates based on the load of the
    server.
*/
class LoadFeeTrack final
{
public:
    explicit LoadFeeTrack (beast::Journal journal = beast::Journal())
        : j_ (journal)
        , localTxnLoadFee_ (lftNormalFee)
        , remoteTxnLoadFee_ (lftNormalFee)
        , clusterTxnLoadFee_ (lftNormalFee)
        , raiseCount_ (0)
    {
    }

    ~LoadFeeTrack() = default;

    void setRemoteFee (std::uint32_t f)
    {
        std::lock_guard <std::mutex> sl (lock_);
        remoteTxnLoadFee_ = f;
    }

    std::uint32_t getRemoteFee () const
    {
        std::lock_guard <std::mutex> sl (lock_);
        return remoteTxnLoadFee_;
    }

    std::uint32_t getLocalFee () const
    {
        std::lock_guard <std::mutex> sl (lock_);
        return localTxnLoadFee_;
    }

    std::uint32_t getClusterFee () const
    {
        std::lock_guard <std::mutex> sl (lock_);
        return clusterTxnLoadFee_;
    }

    std::uint32_t getLoadBase () const
    {
        return lftNormalFee;
    }

    std::uint32_t getLoadFactor () const
    {
        std::lock_guard <std::mutex> sl (lock_);
        return std::max({ clusterTxnLoadFee_, localTxnLoadFee_, remoteTxnLoadFee_ });
    }

    std::pair<std::uint32_t, std::uint32_t>
    getScalingFactors() const
    {
        std::lock_guard<std::mutex> sl(lock_);

        return std::make_pair(
            std::max(localTxnLoadFee_, remoteTxnLoadFee_),
            std::max(remoteTxnLoadFee_, clusterTxnLoadFee_));
    }


    void setClusterFee (std::uint32_t fee)
    {
        std::lock_guard <std::mutex> sl (lock_);
        clusterTxnLoadFee_ = fee;
    }

    bool raiseLocalFee ();
    bool lowerLocalFee ();

    bool isLoadedLocal () const
    {
        std::lock_guard <std::mutex> sl (lock_);
        return (raiseCount_ != 0) || (localTxnLoadFee_ != lftNormalFee);
    }

    bool isLoadedCluster () const
    {
        std::lock_guard <std::mutex> sl (lock_);
        return (raiseCount_ != 0) || (localTxnLoadFee_ != lftNormalFee) ||
            (clusterTxnLoadFee_ != lftNormalFee);
    }

private:
    static std::uint32_t constexpr lftNormalFee = 256;        // 256 is the minimum/normal load factor
    static std::uint32_t constexpr lftFeeIncFraction = 4;     // increase fee by 1/4
    static std::uint32_t constexpr lftFeeDecFraction = 4;     // decrease fee by 1/4
    static std::uint32_t constexpr lftFeeMax = lftNormalFee * 1000000;

    beast::Journal j_;
    std::mutex mutable lock_;

    std::uint32_t localTxnLoadFee_;        // Scale factor, lftNormalFee = normal fee
    std::uint32_t remoteTxnLoadFee_;       // Scale factor, lftNormalFee = normal fee
    std::uint32_t clusterTxnLoadFee_;      // Scale factor, lftNormalFee = normal fee
    std::uint32_t raiseCount_;
};

//------------------------------------------------------------------------------

// Scale from fee units to millionths of a ripple
std::uint64_t scaleFeeBase(std::uint64_t fee, Fees const& fees);

// Scale using load as well as base rate
std::uint64_t scaleFeeLoad(std::uint64_t fee, LoadFeeTrack const& feeTrack,
    Fees const& fees, bool bUnlimited);

} // ripple

#endif