Repository navigation
Expand file tree
/
Copy pathResponseCache.cs
More file actions
250 lines (208 loc) · 8.37 KB
/
Copy pathResponseCache.cs
File metadata and controls
250 lines (208 loc) · 8.37 KB
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
238
239
240
241
242
243
244
245
246
247
248
249
250
using System;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
namespace DnsClient
{
internal class ResponseCache
{
private static readonly TimeSpan s_infiniteTimeout = Timeout.InfiniteTimeSpan;
// max is 24 days
private static readonly TimeSpan s_maxTimeout = TimeSpan.FromMilliseconds(int.MaxValue);
private static readonly TimeSpan s_defaultFailureTimeout = TimeSpan.FromSeconds(5);
private static readonly int s_cleanupInterval = (int)TimeSpan.FromMinutes(10).TotalMilliseconds;
private readonly ConcurrentDictionary<string, ResponseEntry> _cache = new ConcurrentDictionary<string, ResponseEntry>();
private readonly object _cleanupLock = new object();
private bool _cleanupRunning = false;
private int _lastCleanup = 0;
private TimeSpan? _minimumTimeout;
private TimeSpan? _maximumTimeout;
private TimeSpan _failureEntryTimeout = s_defaultFailureTimeout;
public int Count => _cache.Count;
public bool Enabled { get; set; } = true;
public TimeSpan? MinimumTimout
{
get { return _minimumTimeout; }
set
{
if (value.HasValue &&
(value < TimeSpan.Zero || value > s_maxTimeout) && value != s_infiniteTimeout)
{
throw new ArgumentOutOfRangeException(nameof(value));
}
_minimumTimeout = value;
}
}
public TimeSpan? MaximumTimeout
{
get { return _maximumTimeout; }
set
{
if (value.HasValue &&
(value < TimeSpan.Zero || value > s_maxTimeout) && value != s_infiniteTimeout)
{
throw new ArgumentOutOfRangeException(nameof(value));
}
_maximumTimeout = value;
}
}
public TimeSpan FailureEntryTimeout
{
get { return _failureEntryTimeout; }
set
{
if ((value < TimeSpan.Zero || value > s_maxTimeout) && value != s_infiniteTimeout)
{
throw new ArgumentOutOfRangeException(nameof(value));
}
_failureEntryTimeout = value;
}
}
public ResponseCache(bool enabled = true, TimeSpan? minimumTimout = null, TimeSpan? maximumTimeout = null, TimeSpan? failureEntryTimeout = null)
{
Enabled = enabled;
MinimumTimout = minimumTimout;
MaximumTimeout = maximumTimeout;
if (failureEntryTimeout.HasValue)
{
FailureEntryTimeout = failureEntryTimeout.Value;
}
}
public static string GetCacheKey(DnsQuestion question)
{
if (question == null)
{
throw new ArgumentNullException(nameof(question));
}
return string.Concat(question.QueryName.Value, ":", (short)question.QuestionClass, ":", (short)question.QuestionType);
}
public IDnsQueryResponse Get(string key)
{
return Get(key, out double? effectiveTtl);
}
public IDnsQueryResponse Get(string key, out double? effectiveTtl)
{
effectiveTtl = null;
if (key == null) throw new ArgumentNullException(key);
if (!Enabled) return null;
if (_cache.TryGetValue(key, out ResponseEntry entry))
{
effectiveTtl = entry.TTL;
if (entry.IsExpiredFor(DateTimeOffset.UtcNow))
{
_cache.TryRemove(key, out entry);
}
else
{
StartCleanup();
return entry.Response;
}
}
return null;
}
public bool Add(string key, IDnsQueryResponse response, bool cacheFailures = false)
{
if (key == null) throw new ArgumentNullException(key);
if (Enabled && response != null && (cacheFailures || (!response.HasError && response.Answers.Count > 0)))
{
if (response.Answers.Count == 0)
{
// Cache entry for a failure response.
var newEntry = new ResponseEntry(response, FailureEntryTimeout.TotalMilliseconds);
StartCleanup();
return _cache.TryAdd(key, newEntry);
}
else
{
var all = response.AllRecords.Where(p => !(p is Protocol.Options.OptRecord));
if (all.Any())
{
// in millis
double minTtl = all.Min(p => p.InitialTimeToLive) * 1000d;
if (MinimumTimout == Timeout.InfiniteTimeSpan)
{
// TODO: Log warning once?
minTtl = s_maxTimeout.TotalMilliseconds;
}
else if (MinimumTimout.HasValue && minTtl < MinimumTimout.Value.TotalMilliseconds)
{
minTtl = MinimumTimout.Value.TotalMilliseconds;
}
// max TTL check which can limit the upper boundary
if (MaximumTimeout.HasValue && MaximumTimeout != Timeout.InfiniteTimeSpan && minTtl > MaximumTimeout.Value.TotalMilliseconds)
{
minTtl = MaximumTimeout.Value.TotalMilliseconds;
}
if (minTtl < 1d)
{
return false;
}
var newEntry = new ResponseEntry(response, minTtl);
StartCleanup();
return _cache.TryAdd(key, newEntry);
}
}
}
StartCleanup();
return false;
}
private static void DoCleanup(ResponseCache cache)
{
cache._cleanupRunning = true;
var now = DateTimeOffset.UtcNow;
foreach (var entry in cache._cache)
{
if (entry.Value.IsExpiredFor(now))
{
cache._cache.TryRemove(entry.Key, out ResponseEntry o);
}
}
cache._cleanupRunning = false;
}
private void StartCleanup()
{
if (!Enabled)
{
return;
}
// TickCount jump every 25days to int.MinValue, adjusting...
var currentTicks = Environment.TickCount & int.MaxValue;
if (_lastCleanup + s_cleanupInterval < 0 || currentTicks + s_cleanupInterval < 0) _lastCleanup = 0;
if (!_cleanupRunning && _lastCleanup + s_cleanupInterval < currentTicks)
{
lock (_cleanupLock)
{
if (!_cleanupRunning && _lastCleanup + s_cleanupInterval < currentTicks)
{
_lastCleanup = currentTicks;
Task.Factory.StartNew(
state => DoCleanup((ResponseCache)state),
this,
CancellationToken.None,
TaskCreationOptions.DenyChildAttach,
TaskScheduler.Default);
}
}
}
}
private class ResponseEntry
{
public bool IsExpiredFor(DateTimeOffset forDate) => forDate >= ExpiresAt;
public DateTimeOffset ExpiresAt { get; }
public DateTimeOffset Created { get; }
public double TTL { get; set; }
public IDnsQueryResponse Response { get; }
public ResponseEntry(IDnsQueryResponse response, double ttlInMS)
{
Debug.Assert(response != null);
Debug.Assert(ttlInMS >= 0);
Response = response;
TTL = ttlInMS;
Created = DateTimeOffset.UtcNow;
ExpiresAt = Created.AddMilliseconds(TTL);
}
}
}
}