1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
|
/*
* Copyright (c) 2024 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.Utils.Logging;
using VNLib.Plugins.Extensions.Loading;
using VNLib.Data.Caching.Extensions;
using VNLib.Data.Caching.Extensions.Clustering;
namespace VNLib.Data.Caching.ObjectCache.Server.Clustering
{
/*
* This class is responsible for resolving and discovering peer nodes in the cluster network.
*/
internal sealed class PeerDiscoveryManager(
CacheNodeConfiguration config,
ServerClusterConfig clusterConf,
CachePeerMonitor Monitor,
ILogProvider Log,
bool IsDebug,
bool HasWellKnown
)
: IAsyncBackgroundWork, ICachePeerAdapter
{
private readonly List<CacheNodeAdvertisment> _connectedPeers = [];
private readonly VNCacheClusterManager clusterMan = new(config);
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.
*/
//Start the change listener
Task watcher = WatchForPeersAsync(exitToken);
Log.Information("Node discovery worker started, waiting for {idel} to start initial discovery", CacheConstants.Delays.InitialDiscovery);
try
{
await Task.Delay(CacheConstants.Delays.InitialDiscovery, exitToken);
Log.Debug("Begining discovery loop");
while (true)
{
bool wellKnownFailed = false;
try
{
if (IsDebug)
{
Log.Debug("Begining node discovery");
}
/*
* On every loop we will need to resolve well-known servers incase they go down
* or change. There probably should be some more advanced logic and caching here.
*
* Node may not have any well-known nodes, so we need to check for that.
*/
CacheNodeAdvertisment[] wellKnown = HasWellKnown ?
await clusterMan.ResolveWellKnownAsync(exitToken) :
Array.Empty<CacheNodeAdvertisment>();
//Use the monitor to get the initial peers
IEnumerable<CacheNodeAdvertisment> ads = GetMonitorAds();
//Combine well-known peers that are currently connected to this server
CacheNodeAdvertisment[] allAds = ads.Union(wellKnown).ToArray();
if (allAds.Length > 0)
{
//Build the discovery map from all the known nodes to find all known nodes in the entire cluster
await clusterMan.DiscoverNodesAsync(allAds, exitToken);
}
//Log the discovered nodes if verbose logging is enabled
if (IsDebug)
{
CacheNodeAdvertisment[] found = clusterMan.DiscoveredNodes.GetAllNodes();
Log.Debug("Discovered {count} nodes\n\t{nodes}", found.Length, found.Select(static s => s.NodeId));
}
}
catch(OperationCanceledException)
{
throw;
}
catch (Exception ex)
{
Log.Error(ex, "Failed to discover new peer nodes");
}
/*
* If we have well known nodes and the discovery failed, we wait for a shorter
* duration before retrying. This is to avoid spamming the network with requests
* if the well known nodes are down. But if we don't have any well known nodes
* we cannot continue.
*
* This only matters if we are exepcted to have well known nodes.
*/
if(HasWellKnown && wellKnownFailed)
{
if (IsDebug)
{
Log.Debug("Well known node discovery failed, waiting for {idel} before retrying", CacheConstants.Delays.WellKnownResolveFailed);
}
//Wait for shorter duration
await Task.Delay(CacheConstants.Delays.WellKnownResolveFailed, exitToken);
}
else
{
//Delay the next discovery
await Task.Delay(clusterConf.DiscoveryInterval, exitToken);
}
}
}
catch (OperationCanceledException)
{
//Normal exit
Log.Information("Node discovery worker exiting on plugin exit");
}
finally
{
Monitor.Dispose();
}
//Wait for the watcher to exit
await watcher.ConfigureAwait(false);
}
private IEnumerable<CacheNodeAdvertisment> GetMonitorAds()
{
string selfId = (clusterMan.Config as CacheNodeConfiguration)!.NodeId;
return Monitor.GetAllPeers()
.Where(static p => p.Advertisment != null)
//Without us
.Where(n => !string.Equals(n.NodeId, selfId, StringComparison.OrdinalIgnoreCase))
.Select(static p => p.Advertisment!);
}
//Wait for new peers and update the collection
private async Task WatchForPeersAsync(CancellationToken cancellation)
{
try
{
Log.Debug("Discovery worker waiting for new peers to connect");
while (true)
{
//Wait for changes, then get new peers
await Monitor.WaitForChangeAsync().WaitAsync(cancellation);
Log.Verbose("New peers connected");
//Use the monitor to get the initial peers
IEnumerable<CacheNodeAdvertisment> ads = GetMonitorAds();
clusterMan.AddManualNodes(ads);
}
}
catch (OperationCanceledException)
{
//Normal ext
Log.Debug("Connected peer listener exited");
}
}
///<inheritdoc/>
public CacheNodeAdvertisment[] GetNewPeers()
{
lock (_connectedPeers)
{
//Get all discovered peers
CacheNodeAdvertisment[] peers = clusterMan.DiscoveredNodes.GetAllNodes();
//Get the difference between the discovered peers and the connected peers
return peers.Except(_connectedPeers).ToArray();
}
}
///<inheritdoc/>
public void OnPeerListenerAttached(CacheNodeAdvertisment peer)
{
lock (_connectedPeers)
{
//Add to connected peers
_connectedPeers.Add(peer);
}
}
///<inheritdoc/>
public void OnPeerListenerDetatched(CacheNodeAdvertisment peer)
{
//remove from connected peers
lock (_connectedPeers)
{
_connectedPeers.Remove(peer);
}
}
}
}
|
