mirror of
https://github.com/fergalmoran/DnsServer.git
synced 2025-12-22 09:29:50 +00:00
332 lines
13 KiB
C#
332 lines
13 KiB
C#
/*
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Technitium DNS Server
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Copyright (C) 2023 Shreyas Zare (shreyas@technitium.com)
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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using DnsServerCore.ApplicationCommon;
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using System;
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using System.Net;
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using System.Threading;
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using TechnitiumLibrary.Net.Dns.ResourceRecords;
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namespace Failover
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{
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class HealthMonitor : IDisposable
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{
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#region variables
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readonly IDnsServer _dnsServer;
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readonly IPAddress _address;
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readonly string _domain;
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readonly DnsResourceRecordType _type;
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readonly HealthCheck _healthCheck;
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readonly Timer _healthCheckTimer;
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const int HEALTH_CHECK_TIMER_INITIAL_INTERVAL = 1000;
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HealthCheckResponse _lastHealthCheckResponse;
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const int MONITOR_EXPIRY = 1 * 60 * 60 * 1000; //1 hour
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DateTime _lastHealthStatusCheckedOn;
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#endregion
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#region constructor
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public HealthMonitor(IDnsServer dnsServer, IPAddress address, HealthCheck healthCheck, Uri healthCheckUrl)
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{
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_dnsServer = dnsServer;
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_address = address;
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_healthCheck = healthCheck;
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_healthCheckTimer = new Timer(async delegate (object state)
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{
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try
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{
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if (_healthCheck is null)
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{
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_lastHealthCheckResponse = null;
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}
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else
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{
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HealthCheckResponse healthCheckResponse = await _healthCheck.IsHealthyAsync(_address, healthCheckUrl);
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bool statusChanged = false;
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bool maintenance = false;
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if (_lastHealthCheckResponse is null)
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{
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switch (healthCheckResponse.Status)
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{
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case HealthStatus.Failed:
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statusChanged = true;
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break;
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case HealthStatus.Maintenance:
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statusChanged = true;
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maintenance = true;
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break;
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}
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}
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else
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{
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if (_lastHealthCheckResponse.Status != healthCheckResponse.Status)
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{
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statusChanged = true;
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if ((_lastHealthCheckResponse.Status == HealthStatus.Maintenance) || (healthCheckResponse.Status == HealthStatus.Maintenance))
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maintenance = true;
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}
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}
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if (statusChanged)
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{
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switch (healthCheckResponse.Status)
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{
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case HealthStatus.Failed:
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_dnsServer.WriteLog("ALERT! Address [" + _address.ToString() + "] status is FAILED based on '" + _healthCheck.Name + "' health check. The failure reason is: " + healthCheckResponse.FailureReason);
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break;
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default:
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_dnsServer.WriteLog("ALERT! Address [" + _address.ToString() + "] status is " + healthCheckResponse.Status.ToString().ToUpper() + " based on '" + _healthCheck.Name + "' health check.");
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break;
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}
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if (healthCheckResponse.Exception is not null)
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_dnsServer.WriteLog(healthCheckResponse.Exception);
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if (!maintenance)
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{
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//avoid sending email alerts when switching from or to maintenance
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EmailAlert emailAlert = _healthCheck.EmailAlert;
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if (emailAlert is not null)
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_ = emailAlert.SendAlertAsync(_address, _healthCheck.Name, healthCheckResponse);
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}
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WebHook webHook = _healthCheck.WebHook;
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if (webHook is not null)
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_ = webHook.CallAsync(_address, _healthCheck.Name, healthCheckResponse);
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}
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_lastHealthCheckResponse = healthCheckResponse;
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}
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}
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catch (Exception ex)
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{
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_dnsServer.WriteLog(ex);
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if (_lastHealthCheckResponse is null)
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{
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EmailAlert emailAlert = _healthCheck.EmailAlert;
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if (emailAlert is not null)
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_ = emailAlert.SendAlertAsync(_address, _healthCheck.Name, ex);
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WebHook webHook = _healthCheck.WebHook;
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if (webHook is not null)
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_ = webHook.CallAsync(_address, _healthCheck.Name, ex);
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_lastHealthCheckResponse = new HealthCheckResponse(HealthStatus.Failed, ex.ToString(), ex);
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}
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else
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{
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_lastHealthCheckResponse = null;
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}
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}
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finally
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{
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if (!_disposed && (_healthCheck is not null))
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_healthCheckTimer.Change(_healthCheck.Interval, Timeout.Infinite);
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}
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}, null, Timeout.Infinite, Timeout.Infinite);
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_healthCheckTimer.Change(HEALTH_CHECK_TIMER_INITIAL_INTERVAL, Timeout.Infinite);
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}
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public HealthMonitor(IDnsServer dnsServer, string domain, DnsResourceRecordType type, HealthCheck healthCheck, Uri healthCheckUrl)
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{
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_dnsServer = dnsServer;
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_domain = domain;
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_type = type;
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_healthCheck = healthCheck;
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_healthCheckTimer = new Timer(async delegate (object state)
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{
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try
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{
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if (_healthCheck is null)
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{
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_lastHealthCheckResponse = null;
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}
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else
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{
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HealthCheckResponse healthCheckResponse = await _healthCheck.IsHealthyAsync(_domain, _type, healthCheckUrl);
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bool statusChanged = false;
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bool maintenance = false;
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if (_lastHealthCheckResponse is null)
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{
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switch (healthCheckResponse.Status)
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{
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case HealthStatus.Failed:
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statusChanged = true;
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break;
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case HealthStatus.Maintenance:
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statusChanged = true;
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maintenance = true;
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break;
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}
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}
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else
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{
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if (_lastHealthCheckResponse.Status != healthCheckResponse.Status)
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{
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statusChanged = true;
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if ((_lastHealthCheckResponse.Status == HealthStatus.Maintenance) || (healthCheckResponse.Status == HealthStatus.Maintenance))
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maintenance = true;
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}
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}
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if (statusChanged)
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{
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switch (healthCheckResponse.Status)
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{
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case HealthStatus.Failed:
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_dnsServer.WriteLog("ALERT! Domain [" + _domain + "] type [" + _type.ToString() + "] status is FAILED based on '" + _healthCheck.Name + "' health check. The failure reason is: " + healthCheckResponse.FailureReason);
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break;
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default:
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_dnsServer.WriteLog("ALERT! Domain [" + _domain + "] type [" + _type.ToString() + "] status is " + healthCheckResponse.Status.ToString().ToUpper() + " based on '" + _healthCheck.Name + "' health check.");
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break;
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}
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if (healthCheckResponse.Exception is not null)
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_dnsServer.WriteLog(healthCheckResponse.Exception);
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if (!maintenance)
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{
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//avoid sending email alerts when switching from or to maintenance
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EmailAlert emailAlert = _healthCheck.EmailAlert;
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if (emailAlert is not null)
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_ = emailAlert.SendAlertAsync(_domain, _type, _healthCheck.Name, healthCheckResponse);
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}
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WebHook webHook = _healthCheck.WebHook;
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if (webHook is not null)
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_ = webHook.CallAsync(_domain, _type, _healthCheck.Name, healthCheckResponse);
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}
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_lastHealthCheckResponse = healthCheckResponse;
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}
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}
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catch (Exception ex)
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{
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_dnsServer.WriteLog(ex);
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if (_lastHealthCheckResponse is null)
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{
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EmailAlert emailAlert = _healthCheck.EmailAlert;
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if (emailAlert is not null)
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_ = emailAlert.SendAlertAsync(_domain, _type, _healthCheck.Name, ex);
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WebHook webHook = _healthCheck.WebHook;
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if (webHook is not null)
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_ = webHook.CallAsync(_domain, _type, _healthCheck.Name, ex);
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_lastHealthCheckResponse = new HealthCheckResponse(HealthStatus.Failed, ex.ToString(), ex);
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}
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else
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{
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_lastHealthCheckResponse = null;
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}
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}
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finally
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{
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if (!_disposed && (_healthCheck is not null))
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_healthCheckTimer.Change(_healthCheck.Interval, Timeout.Infinite);
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}
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}, null, Timeout.Infinite, Timeout.Infinite);
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_healthCheckTimer.Change(HEALTH_CHECK_TIMER_INITIAL_INTERVAL, Timeout.Infinite);
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}
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#endregion
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#region IDisposable
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bool _disposed;
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protected virtual void Dispose(bool disposing)
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{
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if (_disposed)
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return;
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if (disposing)
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{
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if (_healthCheckTimer is not null)
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_healthCheckTimer.Dispose();
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}
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_disposed = true;
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}
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public void Dispose()
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{
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Dispose(true);
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GC.SuppressFinalize(this);
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}
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#endregion
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#region public
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public bool IsExpired()
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{
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return DateTime.UtcNow > _lastHealthStatusCheckedOn.AddMilliseconds(MONITOR_EXPIRY);
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}
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public void SetUnderMaintenance()
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{
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_lastHealthCheckResponse = new HealthCheckResponse(HealthStatus.Maintenance);
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}
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#endregion
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#region properties
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public IPAddress Address
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{ get { return _address; } }
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public HealthCheckResponse LastHealthCheckResponse
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{
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get
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{
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_lastHealthStatusCheckedOn = DateTime.UtcNow;
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if (_lastHealthCheckResponse is null)
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return new HealthCheckResponse(HealthStatus.Unknown);
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return _lastHealthCheckResponse;
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}
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}
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#endregion
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}
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}
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