Servers/MoonlightServers.Daemon/ServerSystem/Implementations/Docker/DockerStatistics.cs

using Docker.DotNet;
using Docker.DotNet.Models;
using MoonlightServers.Daemon.ServerSystem.Abstractions;

namespace MoonlightServers.Daemon.ServerSystem.Implementations.Docker;

public class DockerStatistics : IRuntimeStatistics, IInstallStatistics
{
    public event Func<ServerStatistics, Task>? OnStatisticsReceived;

    private readonly string ContainerId;
    private readonly DockerClient DockerClient;
    private readonly ILogger Logger;

    private readonly List<ServerStatistics> Cache = new(102);
    private readonly SemaphoreSlim CacheLock = new(1, 1);
    private readonly CancellationTokenSource Cts = new();

    public DockerStatistics(string containerId, DockerClient dockerClient, ILogger logger)
    {
        ContainerId = containerId;
        DockerClient = dockerClient;
        Logger = logger;
    }

    public Task AttachAsync()
    {
        Task.Run(async () =>
        {
            Logger.LogTrace("Streaming loop entered");

            while (!Cts.IsCancellationRequested)
            {
                try
                {
                    await DockerClient.Containers.GetContainerStatsAsync(
                        ContainerId,
                        new ContainerStatsParameters()
                        {
                            Stream = true
                        },
                        new Progress<ContainerStatsResponse>(HandleStatsAsync),
                        Cts.Token
                    );
                }
                catch (OperationCanceledException)
                {
                    // Ignored
                }
                catch (Exception e)
                {
                    Logger.LogError(e, "An unhandled error occured while processing container stats");
                }
            }

            Logger.LogTrace("Streaming loop exited");
        });

        return Task.CompletedTask;
    }

    private async void HandleStatsAsync(ContainerStatsResponse statsResponse)
    {
        try
        {
            var convertedStats = ToServerStatistics(statsResponse);

            await CacheLock.WaitAsync();

            try
            {
                if(Cache.Count > 100)
                    Cache.RemoveRange(0, 30);
                
                Cache.Add(convertedStats);
            }
            finally
            {
                CacheLock.Release();
            }

            if (OnStatisticsReceived != null)
                await OnStatisticsReceived.Invoke(convertedStats);
        }
        catch (Exception e)
        {
            Logger.LogError(e, "An unhandled error occured while handling container stats");
        }
    }

    public async Task ClearCacheAsync()
    {
        await CacheLock.WaitAsync();

        try
        {
            Cache.Clear();
        }
        finally
        {
            CacheLock.Release();
        }
    }

    public async Task<ServerStatistics[]> GetCacheAsync()
    {
        await CacheLock.WaitAsync();

        try
        {
            return Cache.ToArray();
        }
        finally
        {
            CacheLock.Release();
        }
    }

    // Helpers
    public static ServerStatistics ToServerStatistics(ContainerStatsResponse stats)
    {
        double cpuUsage = CalculateCpuUsage(stats);

        ulong usedMemory = stats.MemoryStats?.Usage ?? 0;
        ulong totalMemory = stats.MemoryStats?.Limit ?? 0;

        ulong outgoingNetwork = 0;
        ulong ingoingNetwork = 0;

        if (stats.Networks != null)
        {
            foreach (var network in stats.Networks.Values)
            {
                if (network == null)
                    continue;

                outgoingNetwork += network.TxBytes;
                ingoingNetwork += network.RxBytes;
            }
        }

        ulong writeDisk = stats.StorageStats?.WriteSizeBytes ?? 0;
        ulong readDisk = stats.StorageStats?.ReadSizeBytes ?? 0;

        return new ServerStatistics(
            CpuUsage: cpuUsage,
            UsedMemory: usedMemory,
            TotalMemory: totalMemory,
            OutgoingNetwork: outgoingNetwork,
            IngoingNetwork: ingoingNetwork,
            WriteDisk: writeDisk,
            ReadDisk: readDisk
        );
    }

    private static double CalculateCpuUsage(ContainerStatsResponse stats)
    {
        var cpuStats = stats.CPUStats;
        var preCpuStats = stats.PreCPUStats;

        if (cpuStats == null || preCpuStats == null)
            return 0;

        var cpuUsage = cpuStats.CPUUsage;
        var preCpuUsage = preCpuStats.CPUUsage;

        if (cpuUsage == null || preCpuUsage == null)
            return 0;

        ulong cpuDelta = cpuUsage.TotalUsage - preCpuUsage.TotalUsage;
        ulong systemDelta = cpuStats.SystemUsage - preCpuStats.SystemUsage;

        if (systemDelta == 0 || cpuDelta == 0)
            return 0;

        uint onlineCpus = cpuStats.OnlineCPUs;

        if (onlineCpus == 0 && cpuUsage.PercpuUsage != null)
        {
            onlineCpus = (uint)cpuUsage.PercpuUsage.Count;
        }

        if (onlineCpus == 0)
            onlineCpus = 1;

        return (double)cpuDelta / systemDelta * onlineCpus * 100.0;
    }

    public async ValueTask DisposeAsync()
    {
        await Cts.CancelAsync();
    }
}