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/*
* Copyright (c) 2023 Vaughn Nugent
*
* Library: VNLib
* Package: ObjectCacheServer
* File: PeerDiscoveryManager.cs
*
* PeerDiscoveryManager.cs is part of ObjectCacheServer which is part of the larger
* VNLib collection of libraries and utilities.
*
* ObjectCacheServer 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.
*
* ObjectCacheServer 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.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Collections.Generic;
using VNLib.Plugins;
using VNLib.Utils.Logging;
using VNLib.Data.Caching.Extensions;
using VNLib.Plugins.Extensions.Loading;
namespace VNLib.Data.Caching.ObjectCache.Server.Distribution
{
sealed class PeerDiscoveryManager : IAsyncBackgroundWork, ICachePeerAdapter
{
private readonly List<ICacheNodeAdvertisment> _connectedPeers;
private readonly NodeConfig _config;
private readonly IPeerMonitor _monitor;
private readonly KnownPeerList _knownPeers;
public PeerDiscoveryManager(PluginBase plugin)
{
//Get config
_config = plugin.GetOrCreateSingleton<NodeConfig>();
//Get the peer monitor
_monitor = plugin.GetOrCreateSingleton<CachePeerMonitor>();
//Get the known peer list
_knownPeers = plugin.GetOrCreateSingleton<KnownPeerList>();
_connectedPeers = new();
//Setup discovery error handler
_config.Config.WithErrorHandler(new ErrorHandler(plugin.Log));
}
async Task IAsyncBackgroundWork.DoWorkAsync(ILogProvider pluginLog, CancellationToken exitToken)
{
/*
* This loop uses the peer monitor to keep track of all connected peers, then gets
* all the advertising peers (including known peers) and resolves all nodes across
* the network.
*/
pluginLog.Information("Node discovery worker started");
try
{
while (true)
{
try
{
//Use the monitor to get the initial peers
IEnumerable<ICacheNodeAdvertisment> ads = _monitor.GetAllPeers()
.Where(static p => p.Advertisment != null)
.Select(static p => p.Advertisment!);
//Add known peers to the initial list
ads = ads.Union(_knownPeers.GetPeers());
//Set initial peers
_config.Config.WithInitialPeers(ads);
//Discover all nodes
await _config.Config.DiscoverNodesAsync(exitToken);
}
catch(OperationCanceledException)
{
throw;
}
catch (Exception ex)
{
pluginLog.Error(ex, "Failed to discover new peer nodes");
}
//Delay the next discovery
await Task.Delay(_config.DiscoveryInterval, exitToken);
}
}
catch (OperationCanceledException)
{
//Normal exit
pluginLog.Information("Node discovery worker exiting");
}
finally
{
}
}
///<inheritdoc/>
public ICacheNodeAdvertisment[] GetNewPeers()
{
lock (_connectedPeers)
{
//Get all discovered peers
ICacheNodeAdvertisment[] peers = _config.Config.NodeCollection.GetAllNodes();
//Get the difference between the discovered peers and the connected peers
return peers.Except(_connectedPeers).ToArray();
}
}
///<inheritdoc/>
public void OnPeerListenerAttached(ICacheNodeAdvertisment peer)
{
lock (_connectedPeers)
{
//Add to connected peers
_connectedPeers.Add(peer);
}
}
///<inheritdoc/>
public void OnPeerListenerDetatched(ICacheNodeAdvertisment peer)
{
//remove from connected peers
lock (_connectedPeers)
{
_connectedPeers.Remove(peer);
}
}
private sealed record class ErrorHandler(ILogProvider Logger) : ICacheDiscoveryErrorHandler
{
public void OnDiscoveryError(ICacheNodeAdvertisment errorNode, Exception ex)
{
Logger.Error("Failed to discover nodes from nodeid {nid}, with error\n{err}", errorNode, ex);
}
}
}
}
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