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/*
* Copyright (c) 2023 Vaughn Nugent
*
* Library: VNLib
* Package: VNLib.Plugins.Essentials.Sessions.VNCache
* File: WebSessionProvider.cs
*
* WebSessionProvider.cs is part of VNLib.Plugins.Essentials.Sessions.VNCache which is part of the larger
* VNLib collection of libraries and utilities.
*
* VNLib.Plugins.Essentials.Sessions.VNCache 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.Plugins.Essentials.Sessions.VNCache 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;
using System.Threading.Tasks;
using VNLib.Net.Http;
using VNLib.Utils.Extensions;
using VNLib.Plugins.Essentials;
using VNLib.Plugins.Essentials.Sessions;
using VNLib.Plugins.Extensions.Loading;
namespace VNLib.Plugins.Sessions.VNCache
{
[ConfigurationName(WebSessionProviderEntry.WEB_SESSION_CONFIG)]
internal sealed class WebSessionProvider : ISessionProvider
{
private static readonly SessionHandle _vf = new (null, FileProcessArgs.VirtualSkip, null);
private readonly TimeSpan _validFor;
private readonly WebSessionStore _sessions;
private readonly uint _maxConnections;
private uint _waitingConnections;
public bool IsConnected => _sessions.IsConnected;
public WebSessionProvider(PluginBase plugin, IConfigScope config)
{
_validFor = config["valid_for_sec"].GetTimeSpan(TimeParseType.Seconds);
_maxConnections = config["max_waiting_connections"].GetUInt32();
//Init session provider
_sessions = plugin.GetOrCreateSingleton<WebSessionStore>();
}
private SessionHandle PostProcess(WebSession? session)
{
if (session == null)
{
return SessionHandle.Empty;
}
//Make sure the session has not expired yet
if (session.Created.Add(_validFor) < DateTimeOffset.UtcNow)
{
//Invalidate the session, so its technically valid for this request, but will be cleared on this handle close cycle
session.Invalidate();
//Clear basic login status
session.Token = null;
session.UserID = null;
session.Privilages = 0;
session.SetLoginToken(null);
}
return new SessionHandle(session, OnSessionReleases);
}
private ValueTask OnSessionReleases(ISession session, IHttpEvent entity) => _sessions.ReleaseSessionAsync((WebSession)session, entity);
public ValueTask<SessionHandle> GetSessionAsync(IHttpEvent entity, CancellationToken cancellationToken)
{
//Limit max number of waiting clients and make sure were connected
if (!_sessions.IsConnected || _waitingConnections > _maxConnections)
{
//Set 503 for temporary unavail
entity.CloseResponse(System.Net.HttpStatusCode.ServiceUnavailable);
return ValueTask.FromResult(_vf);
}
ValueTask<WebSession?> result = _sessions.GetSessionAsync(entity, cancellationToken);
if (result.IsCompleted)
{
WebSession? session = result.GetAwaiter().GetResult();
//Post process and get handle for session
SessionHandle handle = PostProcess(session);
return ValueTask.FromResult(handle);
}
else
{
return new(AwaitAsyncGet(result));
}
}
private async Task<SessionHandle> AwaitAsyncGet(ValueTask<WebSession?> async)
{
//Inct wait count while async waiting
_waitingConnections++;
try
{
//await the session
WebSession? session = await async.ConfigureAwait(false);
//return empty session handle if the session could not be found
return PostProcess(session);
}
finally
{
_waitingConnections--;
}
}
}
}
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