/* * Copyright (c) 2018 ETH Zürich, Educational Development and Technology (LET) * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ using System.Threading; using SafeExamBrowser.Contracts.Communication.Events; using SafeExamBrowser.Contracts.Communication.Hosts; using SafeExamBrowser.Contracts.Core.OperationModel; using SafeExamBrowser.Contracts.Logging; using SafeExamBrowser.Contracts.UserInterface; namespace SafeExamBrowser.Client.Operations { /// /// During application shutdown, it could happen that the client stops its communication host before the runtime had the chance to /// disconnect from it. This operation prevents the described race condition by waiting on the runtime to disconnect from the client. /// internal class ClientHostDisconnectionOperation : IOperation { private IClientHost clientHost; private ILogger logger; private int timeout_ms; public IProgressIndicator ProgressIndicator { private get; set; } public ClientHostDisconnectionOperation(IClientHost clientHost, ILogger logger, int timeout_ms) { this.clientHost = clientHost; this.logger = logger; this.timeout_ms = timeout_ms; } public OperationResult Perform() { return OperationResult.Success; } public OperationResult Repeat() { return OperationResult.Success; } public void Revert() { var disconnected = false; var disconnectedEvent = new AutoResetEvent(false); var disconnectedEventHandler = new CommunicationEventHandler(() => disconnectedEvent.Set()); clientHost.RuntimeDisconnected += disconnectedEventHandler; if (clientHost.IsConnected) { logger.Info("Waiting for runtime to disconnect from client communication host..."); disconnected = disconnectedEvent.WaitOne(timeout_ms); if (!disconnected) { logger.Error($"Runtime failed to disconnect within {timeout_ms / 1000} seconds!"); } } else { logger.Info("The runtime has already disconnected from the client communication host."); } clientHost.RuntimeDisconnected -= disconnectedEventHandler; } } }