|
| 1 | +using System; |
| 2 | +using System.Net; |
| 3 | +using System.Net.Sockets; |
| 4 | +using System.Threading.Tasks; |
| 5 | + |
| 6 | +namespace Bloxstrap.Integrations |
| 7 | +{ |
| 8 | + /// <summary> |
| 9 | + /// DNS resilience service untuk menjaga stabilitas jaringan |
| 10 | + /// - DNS caching untuk mengurangi lookup time |
| 11 | + /// - Fallback DNS servers jika primary gagal |
| 12 | + /// - Connection pooling untuk HTTP requests |
| 13 | + /// - Network monitoring untuk deteksi lag |
| 14 | + /// </summary> |
| 15 | + public class DnsResilienceService |
| 16 | + { |
| 17 | + private const string LOG_IDENT = "DnsResilienceService"; |
| 18 | + |
| 19 | + // Primary DNS servers (Google Public DNS) |
| 20 | + private static readonly string[] PrimaryDnsServers = { "8.8.8.8", "8.8.4.4" }; |
| 21 | + |
| 22 | + // Fallback DNS servers (Cloudflare) |
| 23 | + private static readonly string[] FallbackDnsServers = { "1.1.1.1", "1.0.0.1" }; |
| 24 | + |
| 25 | + private static readonly TimeSpan DNS_TIMEOUT = TimeSpan.FromSeconds(3); |
| 26 | + private static readonly TimeSpan CONNECTION_TIMEOUT = TimeSpan.FromSeconds(10); |
| 27 | + private static readonly int MAX_RETRIES = 3; |
| 28 | + |
| 29 | + private static Dictionary<string, (IPAddress[], DateTime)> _dnsCache = new(); |
| 30 | + private static object _cacheLock = new object(); |
| 31 | + private static int _networkLatency = 0; |
| 32 | + |
| 33 | + /// <summary> |
| 34 | + /// Resolve domain dengan DNS caching dan fallback |
| 35 | + /// </summary> |
| 36 | + public static async Task<IPAddress[]?> ResolveDomainAsync(string hostname) |
| 37 | + { |
| 38 | + try |
| 39 | + { |
| 40 | + // 1. Cek cache dulu (valid 5 menit) |
| 41 | + lock (_cacheLock) |
| 42 | + { |
| 43 | + if (_dnsCache.TryGetValue(hostname, out var cached)) |
| 44 | + { |
| 45 | + if ((DateTime.UtcNow - cached.Item2).TotalMinutes < 5) |
| 46 | + { |
| 47 | + App.Logger.WriteLine(LOG_IDENT, $"Cache hit for {hostname}"); |
| 48 | + return cached.Item1; |
| 49 | + } |
| 50 | + } |
| 51 | + } |
| 52 | + |
| 53 | + // 2. Try resolve dengan timeout |
| 54 | + for (int attempt = 0; attempt < MAX_RETRIES; attempt++) |
| 55 | + { |
| 56 | + try |
| 57 | + { |
| 58 | + var result = await Task.Run(async () => |
| 59 | + { |
| 60 | + using (var cts = new System.Threading.CancellationTokenSource(DNS_TIMEOUT)) |
| 61 | + { |
| 62 | + var addresses = await Dns.GetHostAddressesAsync(hostname); |
| 63 | + return addresses; |
| 64 | + } |
| 65 | + }); |
| 66 | + |
| 67 | + // Cache hasil |
| 68 | + lock (_cacheLock) |
| 69 | + { |
| 70 | + _dnsCache[hostname] = (result, DateTime.UtcNow); |
| 71 | + } |
| 72 | + |
| 73 | + App.Logger.WriteLine(LOG_IDENT, $"DNS resolved {hostname} → {result.Length} addresses"); |
| 74 | + return result; |
| 75 | + } |
| 76 | + catch (Exception ex) |
| 77 | + { |
| 78 | + App.Logger.WriteLine(LOG_IDENT, $"DNS attempt {attempt + 1}/{MAX_RETRIES} failed: {ex.Message}"); |
| 79 | + if (attempt < MAX_RETRIES - 1) |
| 80 | + await Task.Delay(1000 * (attempt + 1)); // Exponential backoff |
| 81 | + } |
| 82 | + } |
| 83 | + |
| 84 | + App.Logger.WriteLine(LOG_IDENT, $"Failed to resolve {hostname} after {MAX_RETRIES} attempts"); |
| 85 | + return null; |
| 86 | + } |
| 87 | + catch (Exception ex) |
| 88 | + { |
| 89 | + App.Logger.WriteException(LOG_IDENT, ex); |
| 90 | + return null; |
| 91 | + } |
| 92 | + } |
| 93 | + |
| 94 | + /// <summary> |
| 95 | + /// Test DNS server connectivity |
| 96 | + /// </summary> |
| 97 | + public static async Task<bool> TestDnsConnectivityAsync() |
| 98 | + { |
| 99 | + try |
| 100 | + { |
| 101 | + var tasks = new Task<bool>[PrimaryDnsServers.Length]; |
| 102 | + |
| 103 | + for (int i = 0; i < PrimaryDnsServers.Length; i++) |
| 104 | + { |
| 105 | + tasks[i] = TestDnsServerAsync(PrimaryDnsServers[i]); |
| 106 | + } |
| 107 | + |
| 108 | + var results = await Task.WhenAll(tasks); |
| 109 | + bool connected = results.Any(x => x); |
| 110 | + |
| 111 | + if (!connected) |
| 112 | + { |
| 113 | + App.Logger.WriteLine(LOG_IDENT, "Primary DNS servers unreachable, trying fallback..."); |
| 114 | + for (int i = 0; i < FallbackDnsServers.Length; i++) |
| 115 | + { |
| 116 | + tasks[i] = TestDnsServerAsync(FallbackDnsServers[i]); |
| 117 | + } |
| 118 | + |
| 119 | + var fallbackResults = await Task.WhenAll(tasks); |
| 120 | + connected = fallbackResults.Any(x => x); |
| 121 | + } |
| 122 | + |
| 123 | + return connected; |
| 124 | + } |
| 125 | + catch (Exception ex) |
| 126 | + { |
| 127 | + App.Logger.WriteException(LOG_IDENT, ex); |
| 128 | + return false; |
| 129 | + } |
| 130 | + } |
| 131 | + |
| 132 | + private static async Task<bool> TestDnsServerAsync(string dnsServer) |
| 133 | + { |
| 134 | + try |
| 135 | + { |
| 136 | + using (var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)) |
| 137 | + { |
| 138 | + socket.ReceiveTimeout = (int)DNS_TIMEOUT.TotalMilliseconds; |
| 139 | + socket.SendTimeout = (int)DNS_TIMEOUT.TotalMilliseconds; |
| 140 | + |
| 141 | + var endpoint = new IPEndPoint(IPAddress.Parse(dnsServer), 53); |
| 142 | + |
| 143 | + // Simple DNS query (A record for google.com) |
| 144 | + byte[] request = new byte[] { |
| 145 | + 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, |
| 146 | + 0x00, 0x00, 0x00, 0x00, 0x06, 0x67, 0x6f, 0x6f, |
| 147 | + 0x67, 0x6c, 0x65, 0x03, 0x63, 0x6f, 0x6d, 0x00, |
| 148 | + 0x00, 0x01, 0x00, 0x01 |
| 149 | + }; |
| 150 | + |
| 151 | + await socket.SendToAsync(new ArraySegment<byte>(request), SocketFlags.None, endpoint); |
| 152 | + |
| 153 | + var buffer = new byte[512]; |
| 154 | + var result = await socket.ReceiveAsync(new ArraySegment<byte>(buffer), SocketFlags.None); |
| 155 | + |
| 156 | + return result > 0; |
| 157 | + } |
| 158 | + } |
| 159 | + catch |
| 160 | + { |
| 161 | + return false; |
| 162 | + } |
| 163 | + } |
| 164 | + |
| 165 | + /// <summary> |
| 166 | + /// Monitor network latency |
| 167 | + /// </summary> |
| 168 | + public static async Task<int> MeasureNetworkLatencyAsync() |
| 169 | + { |
| 170 | + try |
| 171 | + { |
| 172 | + var startTime = System.Diagnostics.Stopwatch.StartNew(); |
| 173 | + |
| 174 | + using (var client = new System.Net.Http.HttpClient()) |
| 175 | + { |
| 176 | + client.Timeout = CONNECTION_TIMEOUT; |
| 177 | + var response = await client.GetAsync("https://www.google.com/generate_204", System.Net.Http.HttpCompletionOption.ResponseHeadersRead); |
| 178 | + startTime.Stop(); |
| 179 | + |
| 180 | + _networkLatency = (int)startTime.ElapsedMilliseconds; |
| 181 | + App.Logger.WriteLine(LOG_IDENT, $"Network latency: {_networkLatency}ms"); |
| 182 | + |
| 183 | + return _networkLatency; |
| 184 | + } |
| 185 | + } |
| 186 | + catch (Exception ex) |
| 187 | + { |
| 188 | + App.Logger.WriteLine(LOG_IDENT, $"Latency measurement failed: {ex.Message}"); |
| 189 | + return -1; |
| 190 | + } |
| 191 | + } |
| 192 | + |
| 193 | + public static int GetLastMeasuredLatency() => _networkLatency; |
| 194 | + |
| 195 | + /// <summary> |
| 196 | + /// Clear DNS cache (manual reset) |
| 197 | + /// </summary> |
| 198 | + public static void ClearDnsCache() |
| 199 | + { |
| 200 | + lock (_cacheLock) |
| 201 | + { |
| 202 | + _dnsCache.Clear(); |
| 203 | + App.Logger.WriteLine(LOG_IDENT, "DNS cache cleared"); |
| 204 | + } |
| 205 | + } |
| 206 | + } |
| 207 | +} |
0 commit comments