77 lines
2.5 KiB
C#
77 lines
2.5 KiB
C#
/*
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* Copyright (c) 2022 ETH Zürich, Educational Development and Technology (LET)
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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using System.Threading;
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using SafeExamBrowser.Communication.Contracts.Events;
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using SafeExamBrowser.Core.Contracts.OperationModel;
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using SafeExamBrowser.Core.Contracts.OperationModel.Events;
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using SafeExamBrowser.I18n.Contracts;
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using SafeExamBrowser.Logging.Contracts;
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namespace SafeExamBrowser.Client.Operations
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{
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/// <summary>
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/// During application shutdown, it could happen that the client stops its communication host before the runtime had the chance to
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/// disconnect from it. This operation prevents the described race condition by waiting on the runtime to disconnect from the client.
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/// </summary>
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internal class ClientHostDisconnectionOperation : ClientOperation
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{
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private ILogger logger;
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private int timeout_ms;
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public override event ActionRequiredEventHandler ActionRequired { add { } remove { } }
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public override event StatusChangedEventHandler StatusChanged;
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public ClientHostDisconnectionOperation(ClientContext context, ILogger logger, int timeout_ms) : base(context)
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{
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this.logger = logger;
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this.timeout_ms = timeout_ms;
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}
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public override OperationResult Perform()
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{
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return OperationResult.Success;
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}
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public override OperationResult Revert()
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{
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StatusChanged?.Invoke(TextKey.OperationStatus_WaitRuntimeDisconnection);
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if (Context.ClientHost.IsConnected)
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{
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var disconnected = false;
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var disconnectedEvent = new AutoResetEvent(false);
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var disconnectedEventHandler = new CommunicationEventHandler(() => disconnectedEvent.Set());
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Context.ClientHost.RuntimeDisconnected += disconnectedEventHandler;
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logger.Info("Waiting for runtime to disconnect from client communication host...");
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disconnected = disconnectedEvent.WaitOne(timeout_ms);
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Context.ClientHost.RuntimeDisconnected -= disconnectedEventHandler;
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if (disconnected)
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{
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logger.Info("The runtime has successfully disconnected from the client communication host.");
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}
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else
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{
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logger.Error($"The runtime failed to disconnect within {timeout_ms / 1000} seconds!");
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return OperationResult.Failed;
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}
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}
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else
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{
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logger.Info("The runtime has already disconnected from the client communication host.");
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}
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return OperationResult.Success;
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}
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}
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}
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