DownloadConnectionCount.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
#include "Installer/ChunkSource.h"
#include "Installer/Controllable.h"
#include "BuildPatchManifest.h"
#include "Interfaces/IBuildInstaller.h"
 
enum class EBuildPatchDownloadHealth;
 
namespace BuildPatchServices
{
    class IDownloadServiceStatistics;
    /*
     * An interface for scaling the number of simultaneous download connections
     */
    class IDownloadConnectionCount
    {
    public:
        /*
         * Get the number of simultaneous download connections
         * @param NumProcessing -- the current number of downloads in-flight
         * @param CurrentHealth -- percentage of downloads that have failed since last call to this function, in terms of "health"
         * @return number of connections that should be approximately optimal.
        */
        virtual uint32 GetAdjustedCount(uint32 NumProcessing, EBuildPatchDownloadHealth CurrentHealth) = 0;
        virtual ~IDownloadConnectionCount() {}
    };
 
 
    struct FDownloadConnectionCountConfig
    {
        // Maximum number of simultaneous connections to be used.
        uint32 MaxLimit;
        // Minimum number of connections to be used.
        uint32 MinLimit;
        // How many consecutive decreases in speed must be encountered before the count is changed.
        uint32 NegativeHysteresis;
        // Minimum number of samples needed that constitutes a useful average speed.
        uint32 AverageSpeedMinCount;
        // How many consecutive increases in speed must be encountered before the count is changed.
        uint32 PositiveHysteresis;
        // Percentage of highest seen speed that must be exceeded before the count is changed
        double HighBandwidthFactor;
        // Percentage of highest seen speed that must be fallen short of before the count is changed
        double LowBandwidthFactor;
        // Enable or disable download scaling.
        bool bDisableConnectionScaling;
        // The number of connections to allow when dynamic scaling is disabled
        uint32 FallbackCount;
        // How many consecutive poor download health status checks must be encountered before the count is changed.
        uint32 HealthHysteresis;
 
        FDownloadConnectionCountConfig()
            : MaxLimit(100U)
            , MinLimit(8U)
            , NegativeHysteresis(8U)
            , AverageSpeedMinCount(8U)
            , PositiveHysteresis(4U)
            , HighBandwidthFactor(0.85L)
            , LowBandwidthFactor(0.65L)
            , bDisableConnectionScaling(false)
            , FallbackCount(16)
            , HealthHysteresis(8)
        {
        }
        FDownloadConnectionCountConfig(const FDownloadConnectionCountConfig& CopyThis)
            : MaxLimit(CopyThis.MaxLimit)
            , MinLimit(CopyThis.MinLimit)
            , NegativeHysteresis(CopyThis.NegativeHysteresis)
            , AverageSpeedMinCount(CopyThis.AverageSpeedMinCount)
            , PositiveHysteresis(CopyThis.PositiveHysteresis)
            , HighBandwidthFactor(CopyThis.HighBandwidthFactor)
            , LowBandwidthFactor(CopyThis.LowBandwidthFactor)
            , bDisableConnectionScaling(CopyThis.bDisableConnectionScaling)
            , FallbackCount(CopyThis.FallbackCount)
            , HealthHysteresis(CopyThis.HealthHysteresis)
        {
 
        }
    };
 
    class FDownloadConnectionCountFactory
    {
    public:
        /*
         * Create a download connection count calculator.
         * @param Configuration -- configuration values.
         * @param InDownloadStatistics -- A download statistics object. Can be null. If null, the object will use an implementation that does not take into account download speed changes.
        */
        static IDownloadConnectionCount* Create(FDownloadConnectionCountConfig Configuration, IDownloadServiceStatistics* InDownloadStatistics);
    };
}