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/*
* Copyright (c) 2023 Vaughn Nugent
*
* Library: VNLib
* Package: VNLib.Data.Caching
* File: ClientRetryManager.cs
*
* ClientRetryManager.cs is part of VNLib.Data.Caching which is part of the larger
* VNLib collection of libraries and utilities.
*
* VNLib.Data.Caching is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* VNLib.Data.Caching is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see https://www.gnu.org/licenses/.
*/
using System;
using System.Threading.Tasks;
using System.Security.Cryptography;
using VNLib.Utils;
using VNLib.Net.Messaging.FBM.Client;
namespace VNLib.Data.Caching
{
/// <summary>
/// Manages a <see cref="IStatefulConnection"/> reconnect policy
/// </summary>
public class ClientRetryManager<T> : VnDisposeable where T: IStatefulConnection
{
const int RetryRandMaxMsDelay = 1000;
private readonly TimeSpan RetryDelay;
private readonly T Client;
private readonly Uri ServerUri;
internal ClientRetryManager(T worker, TimeSpan delay, Uri serverUri)
{
this.Client = worker;
this.RetryDelay = delay;
this.ServerUri = serverUri;
//Register disconnect listener
worker.ConnectionClosed += Worker_Disconnected;
}
private void Worker_Disconnected(object? sender, EventArgs args)
{
//Exec retry on exit
_ = RetryAsync().ConfigureAwait(false);
}
/// <summary>
/// Raised before client is to be reconnected
/// </summary>
public event Action<T>? OnBeforeReconnect;
/// <summary>
/// Raised when the client fails to reconnect. Should return a value that instructs the
/// manager to reconnect
/// </summary>
public event Func<T, Exception, bool>? OnReconnectFailed;
async Task RetryAsync()
{
//Begin random delay with retry ms
int randomDelayMs = (int)RetryDelay.TotalMilliseconds;
//random delay to add to prevent retry-storm
randomDelayMs += RandomNumberGenerator.GetInt32(RetryRandMaxMsDelay);
//Retry loop
bool retry = true;
while (retry)
{
try
{
//Inform Listener for the retry
OnBeforeReconnect?.Invoke(Client);
//wait for delay before reconnecting
await Task.Delay(randomDelayMs);
//Reconnect async
await Client.ConnectAsync(ServerUri).ConfigureAwait(false);
break;
}
catch (Exception Ex)
{
//Invoke error handler, may be null, incase exit
retry = OnReconnectFailed?.Invoke(Client, Ex) ?? false;
}
}
}
///<inheritdoc/>
protected override void Free()
{
//Unregister the event listener
Client.ConnectionClosed -= Worker_Disconnected;
}
}
}
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