Support --ephemeral flag (#660)

This optional flag will configure the runner to only take one job, and let the service un-configure the runner after that job finishes.

src/Runner.Common/ConfigurationStore.cs

@@ -33,6 +33,9 @@ namespace GitHub.Runner.Common
         [DataMember(EmitDefaultValue = false)]
         public string PoolName { get; set; }
 
+        [DataMember(EmitDefaultValue = false)]
+        public bool Ephemeral { get; set; }
+
         [DataMember(EmitDefaultValue = false)]
         public string ServerUrl { get; set; }
 

src/Runner.Common/Constants.cs

@@ -125,9 +125,10 @@ namespace GitHub.Runner.Common
                 {
                     public static readonly string Check = "check";
                     public static readonly string Commit = "commit";
+                    public static readonly string Ephemeral = "ephemeral";
                     public static readonly string Help = "help";
                     public static readonly string Replace = "replace";
-                    public static readonly string Once = "once";
+                    public static readonly string Once = "once"; // TODO: Remove in 10/2021
                     public static readonly string RunAsService = "runasservice";
                     public static readonly string Unattended = "unattended";
                     public static readonly string Version = "version";

src/Runner.Listener/CommandSettings.cs

@@ -29,10 +29,10 @@ namespace GitHub.Runner.Listener
         {
             Constants.Runner.CommandLine.Flags.Check,
             Constants.Runner.CommandLine.Flags.Commit,
+            Constants.Runner.CommandLine.Flags.Ephemeral,
             Constants.Runner.CommandLine.Flags.Help,
             Constants.Runner.CommandLine.Flags.Replace,
             Constants.Runner.CommandLine.Flags.RunAsService,
-            Constants.Runner.CommandLine.Flags.Once,
             Constants.Runner.CommandLine.Flags.Unattended,
             Constants.Runner.CommandLine.Flags.Version
         };
@@ -66,7 +66,9 @@ namespace GitHub.Runner.Listener
         public bool Help => TestFlag(Constants.Runner.CommandLine.Flags.Help);
         public bool Unattended => TestFlag(Constants.Runner.CommandLine.Flags.Unattended);
         public bool Version => TestFlag(Constants.Runner.CommandLine.Flags.Version);
+        public bool Ephemeral => TestFlag(Constants.Runner.CommandLine.Flags.Ephemeral);
 
+        // TODO: Remove in 10/2021
         public bool RunOnce => TestFlag(Constants.Runner.CommandLine.Flags.Once);
 
         // Constructor.

src/Runner.Listener/Configuration/ConfigurationManager.cs

@@ -195,6 +195,7 @@ namespace GitHub.Runner.Listener.Configuration
             TaskAgent agent;
             while (true)
             {
+                runnerSettings.Ephemeral = command.Ephemeral;
                 runnerSettings.AgentName = command.GetRunnerName();
 
                 _term.WriteLine();
@@ -211,7 +212,7 @@ namespace GitHub.Runner.Listener.Configuration
                     if (command.GetReplace())
                     {
                         // Update existing agent with new PublicKey, agent version.
-                        agent = UpdateExistingAgent(agent, publicKey, userLabels);
+                        agent = UpdateExistingAgent(agent, publicKey, userLabels, runnerSettings.Ephemeral);
 
                         try
                         {
@@ -234,7 +235,7 @@ namespace GitHub.Runner.Listener.Configuration
                 else
                 {
                     // Create a new agent.
-                    agent = CreateNewAgent(runnerSettings.AgentName, publicKey, userLabels);
+                    agent = CreateNewAgent(runnerSettings.AgentName, publicKey, userLabels, runnerSettings.Ephemeral);
 
                     try
                     {
@@ -456,7 +457,7 @@ namespace GitHub.Runner.Listener.Configuration
         }
 
 
-        private TaskAgent UpdateExistingAgent(TaskAgent agent, RSAParameters publicKey, ISet<string> userLabels)
+        private TaskAgent UpdateExistingAgent(TaskAgent agent, RSAParameters publicKey, ISet<string> userLabels, bool ephemeral)
         {
             ArgUtil.NotNull(agent, nameof(agent));
             agent.Authorization = new TaskAgentAuthorization
@@ -467,6 +468,8 @@ namespace GitHub.Runner.Listener.Configuration
             // update should replace the existing labels
             agent.Version = BuildConstants.RunnerPackage.Version;
             agent.OSDescription = RuntimeInformation.OSDescription;
+            agent.Ephemeral = ephemeral;
+            agent.MaxParallelism = 1;
 
             agent.Labels.Clear();
 
@@ -482,7 +485,7 @@ namespace GitHub.Runner.Listener.Configuration
             return agent;
         }
 
-        private TaskAgent CreateNewAgent(string agentName, RSAParameters publicKey, ISet<string> userLabels)
+        private TaskAgent CreateNewAgent(string agentName, RSAParameters publicKey, ISet<string> userLabels, bool ephemeral)
         {
             TaskAgent agent = new TaskAgent(agentName)
             {
@@ -493,6 +496,7 @@ namespace GitHub.Runner.Listener.Configuration
                 MaxParallelism = 1,
                 Version = BuildConstants.RunnerPackage.Version,
                 OSDescription = RuntimeInformation.OSDescription,
+                Ephemeral = ephemeral,
             };
 
             agent.Labels.Add(new AgentLabel("self-hosted", LabelType.System));

src/Runner.Listener/Runner.cs

@@ -234,7 +234,7 @@ namespace GitHub.Runner.Listener
                     HostContext.StartupType = startType;
 
                     // Run the runner interactively or as service
-                    return await RunAsync(settings, command.RunOnce);
+                    return await RunAsync(settings, command.RunOnce || settings.Ephemeral);  // TODO: Remove RunOnce later.
                 }
                 else
                 {
@@ -466,8 +466,16 @@ namespace GitHub.Runner.Listener
                         await jobDispatcher.ShutdownAsync();
                     }
 
-                    //TODO: make sure we don't mask more important exception
+                    try
+                    {
                         await _listener.DeleteSessionAsync();
+                    }
+                    catch (Exception ex) when (runOnce)
+                    {
+                        // ignore exception during delete session for ephemeral runner since the runner might already be deleted from the server side
+                        // and the delete session call will ends up with 401.
+                        Trace.Info($"Ignore any exception during DeleteSession for an ephemeral runner. {ex}");
+                    }
 
                     messageQueueLoopTokenSource.Dispose();
                 }
@@ -512,7 +520,9 @@ Config Options:
  --labels string        Extra labels in addition to the default: 'self-hosted,{Constants.Runner.Platform},{Constants.Runner.PlatformArchitecture}'
  --work string          Relative runner work directory (default {Constants.Path.WorkDirectory})
  --replace              Replace any existing runner with the same name (default false)
- --pat                  GitHub personal access token used for checking network connectivity when executing `.{separator}run.{ext} --check`");
+ --pat                  GitHub personal access token used for checking network connectivity when executing `.{separator}run.{ext} --check`
+ --ephemeral            Configure the runner to only take one job and then let the service un-configure the runner after the job finishes (default false)");
+
 #if OS_WINDOWS
     _term.WriteLine($@" --runasservice   Run the runner as a service");
     _term.WriteLine($@" --windowslogonaccount string   Account to run the service as. Requires runasservice");

src/Sdk/DTWebApi/WebApi/TaskAgentReference.cs

@@ -24,6 +24,7 @@ namespace GitHub.DistributedTask.WebApi
             this.OSDescription = referenceToBeCloned.OSDescription;
             this.ProvisioningState = referenceToBeCloned.ProvisioningState;
             this.AccessPoint = referenceToBeCloned.AccessPoint;
+            this.Ephemeral = referenceToBeCloned.Ephemeral;
 
             if (referenceToBeCloned.m_links != null)
             {
@@ -81,6 +82,16 @@ namespace GitHub.DistributedTask.WebApi
             set;
         }
 
+        /// <summary>
+        /// Signifies that this Agent can only run one job and will be removed by the server after that one job finish.
+        /// </summary>
+        [DataMember]
+        public bool? Ephemeral
+        {
+            get;
+            set;
+        }
+
         /// <summary>
         /// Whether or not the agent is online.
         /// </summary>

src/Test/L0/Listener/RunnerL0.cs

@@ -243,7 +243,8 @@ namespace GitHub.Runner.Common.Tests.Listener
                 runner.Initialize(hc);
                 var settings = new RunnerSettings
                 {
-                    PoolId = 43242
+                    PoolId = 43242,
+                    Ephemeral = true
                 };
 
                 var message = new TaskAgentMessage()
@@ -294,7 +295,7 @@ namespace GitHub.Runner.Common.Tests.Listener
 
                 _configStore.Setup(x => x.IsServiceConfigured()).Returns(false);
                 //Act
-                var command = new CommandSettings(hc, new string[] { "run", "--once" });
+                var command = new CommandSettings(hc, new string[] { "run" });
                 Task<int> runnerTask = runner.ExecuteCommand(command);
 
                 //Assert
@@ -332,7 +333,8 @@ namespace GitHub.Runner.Common.Tests.Listener
                 runner.Initialize(hc);
                 var settings = new RunnerSettings
                 {
-                    PoolId = 43242
+                    PoolId = 43242,
+                    Ephemeral = true
                 };
 
                 var message1 = new TaskAgentMessage()
@@ -390,7 +392,7 @@ namespace GitHub.Runner.Common.Tests.Listener
 
                 _configStore.Setup(x => x.IsServiceConfigured()).Returns(false);
                 //Act
-                var command = new CommandSettings(hc, new string[] { "run", "--once" });
+                var command = new CommandSettings(hc, new string[] { "run" });
                 Task<int> runnerTask = runner.ExecuteCommand(command);
 
                 //Assert
@@ -431,7 +433,8 @@ namespace GitHub.Runner.Common.Tests.Listener
                 var settings = new RunnerSettings
                 {
                     PoolId = 43242,
-                    AgentId = 5678
+                    AgentId = 5678,
+                    Ephemeral = true
                 };
 
                 var message1 = new TaskAgentMessage()
@@ -475,7 +478,7 @@ namespace GitHub.Runner.Common.Tests.Listener
 
                 _configStore.Setup(x => x.IsServiceConfigured()).Returns(false);
                 //Act
-                var command = new CommandSettings(hc, new string[] { "run", "--once" });
+                var command = new CommandSettings(hc, new string[] { "run" });
                 Task<int> runnerTask = runner.ExecuteCommand(command);
 
                 //Assert