server wrapper for pulling full job message (#1933)

src/Runner.Common/RunServer.cs

@@ -0,0 +1,76 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.Serialization;
+using System.Threading;
+using System.Threading.Tasks;
+using GitHub.DistributedTask.Pipelines;
+using GitHub.DistributedTask.WebApi;
+using GitHub.Runner.Common.Util;
+using GitHub.Runner.Sdk;
+using GitHub.Services.Common;
+using GitHub.Services.WebApi;
+
+namespace GitHub.Runner.Common
+{
+    [ServiceLocator(Default = typeof(RunServer))]
+    public interface IRunServer : IRunnerService
+    {
+        Task ConnectAsync(Uri serverUrl, VssCredentials credentials);
+
+        Task<AgentJobRequestMessage> GetJobMessageAsync(string id);
+    }
+
+    public sealed class RunServer : RunnerService, IRunServer
+    {
+        private bool _hasConnection;
+        private VssConnection _connection;
+        private TaskAgentHttpClient _taskAgentClient;
+
+        public async Task ConnectAsync(Uri serverUrl, VssCredentials credentials)
+        {
+            _connection = await EstablishVssConnection(serverUrl, credentials, TimeSpan.FromSeconds(100));
+            _taskAgentClient = _connection.GetClient<TaskAgentHttpClient>();
+            _hasConnection = true;
+        }
+
+        private async Task<VssConnection> EstablishVssConnection(Uri serverUrl, VssCredentials credentials, TimeSpan timeout)
+        {
+            Trace.Info($"EstablishVssConnection");
+            Trace.Info($"Establish connection with {timeout.TotalSeconds} seconds timeout.");
+            int attemptCount = 5;
+            while (attemptCount-- > 0)
+            {
+                var connection = VssUtil.CreateConnection(serverUrl, credentials, timeout: timeout);
+                try
+                {
+                    await connection.ConnectAsync();
+                    return connection;
+                }
+                catch (Exception ex) when (attemptCount > 0)
+                {
+                    Trace.Info($"Catch exception during connect. {attemptCount} attempt left.");
+                    Trace.Error(ex);
+
+                    await HostContext.Delay(TimeSpan.FromMilliseconds(100), CancellationToken.None);
+                }
+            }
+
+            // should never reach here.
+            throw new InvalidOperationException(nameof(EstablishVssConnection));
+        }
+
+        private void CheckConnection()
+        {
+            if (!_hasConnection)
+            {
+                throw new InvalidOperationException($"SetConnection");
+            }
+        }
+
+        public Task<AgentJobRequestMessage> GetJobMessageAsync(string id)
+        {
+            CheckConnection();
+            return _taskAgentClient.GetJobMessageAsync(id);
+        }
+    }
+}