frostfs-sdk-csharp/src/FrostFS.SDK.ClientV2/Poll/ClientWrapper.cs

using System.Threading.Tasks;

namespace FrostFS.SDK.ClientV2;

// clientWrapper is used by default, alternative implementations are intended for testing purposes only.
public class ClientWrapper
{
    private readonly object _lock = new();

    public ClientWrapper(WrapperPrm wrapperPrm)
    {
        WrapperPrm = wrapperPrm;
        StatusMonitor = new ClientStatusMonitor(wrapperPrm.Logger, wrapperPrm.Address, wrapperPrm.ErrorThreshold);

        try
        {
            Client = new FrostFSClient(WrapperPrm);
            StatusMonitor.SetHealthy();
        }
        catch (FrostFsException)
        {
        }
    }

    internal FrostFSClient? Client { get; private set; }

    internal WrapperPrm WrapperPrm { get; }

    internal ClientStatusMonitor StatusMonitor { get; }

    internal FrostFSClient? GetClient()
    {
        lock (_lock)
        {
            if (StatusMonitor.IsHealthy())
            {
                return Client;
            }

            return null;
        }
    }

    // dial establishes a connection to the server from the FrostFS network.
    // Returns an error describing failure reason. If failed, the client
    // SHOULD NOT be used.
    internal async Task<string?> Dial(CallContext ctx)
    {
        var client = GetClient();

        if (client == null)
            return "pool client unhealthy";

        var result = await client.Dial(ctx).ConfigureAwait(false);
        if (!string.IsNullOrEmpty(result))
        {
            StatusMonitor.SetUnhealthyOnDial();
            return result;
        }

        return null;
    }

    private async Task ScheduleGracefulClose()
    {
        if (Client == null)
            return;

        await Task.Delay((int)WrapperPrm.GracefulCloseOnSwitchTimeout).ConfigureAwait(false);

        Client.Close();
    }

    // restartIfUnhealthy checks healthy status of client and recreate it if status is unhealthy.
    // Indicating if status was changed by this function call and returns error that caused unhealthy status.
    internal async Task<bool> RestartIfUnhealthy(CallContext ctx)
    {
        bool wasHealthy;

        try
        {
            var prmNodeInfo = new PrmNodeInfo { Context = ctx };
            var response = await Client!.GetNodeInfoAsync(prmNodeInfo).ConfigureAwait(false);
            return false;
        }
        catch (FrostFsException)
        {
            wasHealthy = true;
        }

        // if connection is dialed before, to avoid routine/connection leak,
        // pool has to close it and then initialize once again.
        if (StatusMonitor.IsDialed())
        {
            await ScheduleGracefulClose().ConfigureAwait(false);
        }

#pragma warning disable CA2000 // Dispose objects before losing scope: will be disposed manually
        FrostFSClient client = new(WrapperPrm);
#pragma warning restore CA2000

        //TODO: set additioanl params          
        var error = await client.Dial(ctx).ConfigureAwait(false);
        if (!string.IsNullOrEmpty(error))
        {
            StatusMonitor.SetUnhealthyOnDial();
            return wasHealthy;
        }

        lock (_lock)
        {
            Client = client;
        }

        try
        {
            var prmNodeInfo = new PrmNodeInfo { Context = ctx };
            var res = await client.GetNodeInfoAsync(prmNodeInfo).ConfigureAwait(false);
        }
        catch (FrostFsException)
        {
            StatusMonitor.SetUnhealthy();
            return wasHealthy;
        }

        StatusMonitor.SetHealthy();
        return !wasHealthy;
    }

    internal void IncRequests(ulong elapsed, MethodIndex method)
    {
        var methodStat = StatusMonitor.Methods[(int)method];

        methodStat.IncRequests(elapsed);
    }
}