Add option to keep the child process alive

src/Microsoft.Crank.Agent/Startup.cs

@@ -1733,6 +1733,12 @@ async Task StopJobAsync(bool abortCollection = false)
 
                                     foreach (var processId in job.AllProcessIds)
                                     {
+                                        // Should we keep the child process alive?
+                                        if (processId == job.ChildProcessId && job.KeepChildProcessAlive)
+                                        {
+                                            continue;
+                                        }
+
                                         Process localProcess;
 
                                         try
@@ -4727,6 +4733,7 @@ private static async Task<Process> StartProcess(string hostname, string benchmar
             process.ErrorDataReceived += (_, e) =>
             {
                 const string processIdMarker = "##ChildProcessId:";
+                const string keepAliveMarker = "KeepAlive:";
 
                 if (e != null && e.Data != null)
                 {
@@ -4743,12 +4750,24 @@ private static async Task<Process> StartProcess(string hostname, string benchmar
                     }
 
                     // Detect the app is wrapping a child process
-                    if (e.Data.StartsWith(processIdMarker)
-                        && int.TryParse(e.Data.Substring(processIdMarker.Length), out var childProcessId))
+                    if (e.Data.Trim().StartsWith(processIdMarker))
                     {
-                        Log.Info($"Tracking child process id: {childProcessId}");
-                        job.ChildProcessId = childProcessId;
-                        stopwatch.Restart();
+                        // ##ChildProcessId: 12345[; KeepAlive: true]
+                        var segments = e.Data.Split(';', 2); // Max 2 arguments
+
+                        if (int.TryParse(segments[0].Trim().AsSpan(processIdMarker.Length), out var childProcessId))
+                        {
+                            Log.Info($"Tracking child process id: {childProcessId}");
+                            job.ChildProcessId = childProcessId;
+                            stopwatch.Restart();
+                        }
+
+                        if (segments.Length > 1 && 
+                            segments[1].Trim().StartsWith(keepAliveMarker, StringComparison.OrdinalIgnoreCase) && 
+                            bool.TryParse(segments[1].Trim().AsSpan(keepAliveMarker.Length), out var keepAlive) && keepAlive)
+                        {
+                            job.KeepChildProcessAlive = true;
+                        }
                     }
                 }
             };

src/Microsoft.Crank.Controller/Documentation.cs

@@ -90,6 +90,7 @@ out of 1200% total available CPU time.
   ## Debugging
 
   --[JOB].noClean <true|false>                                  Whether to keep the work folder on the server or not. Default is false, such that each job is cleaned once it's finished.
+  --[JOB].keepChildProcessAlive <true|false>                    Whether to keep the child process, if tracked, alive. Default is false.
   --[JOB].options.fetch <true|false>                            Whether the benchmark folder is downloaded. e.g., true. For Docker see '--[JOB].dockerFetchPath'
   --[JOB].options.fetchOutput <filename>                        The name of the fetched archive. Can be a file prefix (app will add *.DATE*.zip) , or a specific name (end in *.zip) and no DATE* will be added e.g., c:\publishedapps\myApp
   --[JOB].options.displayOutput <true|false>                    Whether to download and display the standard output of the benchmark.

src/Microsoft.Crank.Controller/README.md

@@ -144,6 +144,7 @@ Run 'crank [command] -?|-h|--help' for more information about a command.
   ## Debugging
 
   --[JOB].noClean <true|false>                                  Whether to keep the work folder on the server or not. Default is false, such that each job is cleaned once it's finished.
+  --[JOB].keepChildProcessAlive <true|false>                    Whether to keep the child process, if tracked, alive. Default is false.
   --[JOB].options.fetch <true|false>                            Whether the benchmark folder is downloaded. e.g., true. For Docker see '--[JOB].dockerFetchPath'
   --[JOB].options.fetchOutput <filename>                        The name of the fetched archive. Can be a file prefix (app will add *.DATE*.zip) , or a specific name (end in *.zip) and no DATE* will be added e.g., c:\publishedapps\myApp
   --[JOB].options.displayOutput <true|false>                    Whether to download and display the standard output of the benchmark.

src/Microsoft.Crank.EventSources/BenchmarksEventSource.cs

@@ -60,9 +60,10 @@ public static void MeasureAndRegister(string name, string value, string descript
         /// <summary>
         /// Instructs the host agent to track CPU and memory usage for the specified process id.
         /// </summary>
-        public static void SetChildProcessId(int pid)
+        public static void SetChildProcessId(int pid, bool? keepAlive = null)
         {
-            Console.Error.WriteLine($"##ChildProcessId:{pid}");
+            keepAlive ??= false;
+            Console.Error.WriteLine($"##ChildProcessId:{pid};KeepAlive:{keepAlive}");
         }
 
         /// <summary>

src/Microsoft.Crank.EventSources/Microsoft.Crank.EventSources.csproj

@@ -6,7 +6,8 @@
     <Description>Helper classes to register metrics with the Microsoft.Crank tools.</Description>
     <IsPackable>true</IsPackable>
     <Authors>Microsoft</Authors>
-    <PackageId>Microsoft.Crank.EventSources</PackageId>    
+    <PackageId>Microsoft.Crank.EventSources</PackageId>
+    <LangVersion>Latest</LangVersion>
   </PropertyGroup>
 
 </Project>

src/Microsoft.Crank.Jobs.Bombardier/Microsoft.Crank.Jobs.Bombardier.csproj

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>net8.0</TargetFramework>
+    <LangVersion>Latest</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

src/Microsoft.Crank.Models/Job.cs

@@ -220,6 +220,7 @@ public Source Source
         public string BasePath { get; set; }
         public int ProcessId { get; set; }
         public int ChildProcessId { get; set; }
+        public bool KeepChildProcessAlive { get; set; } = false;
         public int ActiveProcessId => ChildProcessId > 0 ? ChildProcessId : ProcessId;
         public int[] AllProcessIds => ChildProcessId > 0 ? [ChildProcessId, ProcessId] : [ProcessId];
         public Dictionary<string, string> EnvironmentVariables { get; } = [];