projectmodelserver

src/dotnet-projectmodel-server/ProtocolManager.cs

@@ -0,0 +1,111 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+using Microsoft.Extensions.Logging;
+using Newtonsoft.Json.Linq;
+
+namespace Microsoft.DotNet.ProjectModel.Server
+{
+    internal class ProtocolManager
+    {
+        /// <summary>
+        /// Environment variable for overriding protocol.
+        /// </summary>
+        public const string EnvDthProtocol = "DTH_PROTOCOL";
+
+        private readonly ILogger _log;
+
+        public ProtocolManager(int maxVersion, ILoggerFactory loggerFactory)
+        {
+            MaxVersion = maxVersion;
+            _log = loggerFactory.CreateLogger<ProtocolManager>();
+
+            // initialized to the highest supported version or environment overridden value
+            int? protocol = GetProtocolVersionFromEnvironment();
+
+            if (protocol.HasValue)
+            {
+                CurrentVersion = protocol.Value;
+                EnvironmentOverridden = true;
+            }
+            else
+            {
+                CurrentVersion = 4;
+            }
+        }
+
+        public int MaxVersion { get; }
+
+        public int CurrentVersion { get; private set; }
+
+        public bool EnvironmentOverridden { get; }
+
+        public bool IsProtocolNegotiation(Message message)
+        {
+            return message?.MessageType == MessageTypes.ProtocolVersion;
+        }
+
+        public void Negotiate(Message message)
+        {
+            if (!IsProtocolNegotiation(message))
+            {
+                return;
+            }
+
+            _log.LogInformation("Initializing the protocol negotiation.");
+
+            if (EnvironmentOverridden)
+            {
+                _log.LogInformation($"DTH protocol negotiation is override by environment variable {EnvDthProtocol} and set to {CurrentVersion}.");
+                return;
+            }
+
+            var tokenValue = message.Payload?["Version"];
+            if (tokenValue == null)
+            {
+                _log.LogInformation("Protocol negotiation failed. Version property is missing in payload.");
+                return;
+            }
+
+            var preferredVersion = tokenValue.ToObject<int>();
+            if (preferredVersion == 0)
+            {
+                // the preferred version can't be zero. either property is missing or the the payload is corrupted.
+                _log.LogInformation("Protocol negotiation failed. Protocol version 0 is invalid.");
+                return;
+            }
+
+            CurrentVersion = Math.Min(preferredVersion, MaxVersion);
+            _log.LogInformation($"Protocol negotiation successed. Use protocol {CurrentVersion}");
+
+            if (message.Sender != null)
+            {
+                _log.LogInformation("Respond to protocol negotiation.");
+                message.Sender.Transmit(Message.FromPayload(
+                    MessageTypes.ProtocolVersion,
+                    0,
+                    new { Version = CurrentVersion }));
+            }
+            else
+            {
+                _log.LogInformation($"{nameof(Message.Sender)} is null.");
+            }
+        }
+
+        private static int? GetProtocolVersionFromEnvironment()
+        {
+            // look for the environment variable DTH_PROTOCOL, if it is set override the protocol version.
+            // this is for debugging.
+            var strProtocol = Environment.GetEnvironmentVariable(EnvDthProtocol);
+            int intProtocol = -1;
+            if (!string.IsNullOrEmpty(strProtocol) && Int32.TryParse(strProtocol, out intProtocol))
+            {
+                return intProtocol;
+            }
+
+            return null;
+        }
+    }
+}