implementd AsBooleanStrict and check in JobRunner

src/Agent.Worker/JobRunner.cs

@@ -334,6 +334,25 @@ namespace Microsoft.VisualStudio.Services.Agent.Worker
                     return await CompleteJobAsync(jobServer, jobContext, message, TaskResult.Failed);
                 }
 
+                // check if knob DrainQueuesAfterTask has correct value
+                bool defaultDrainQueuesAfterTask = AgentKnobs.DrainQueuesAfterTask.GetValue<BuiltInDefaultKnobSource>(jobContext).AsBoolean();
+                try
+                {
+                    AgentKnobs.DrainQueuesAfterTask.GetValue(jobContext).AsBooleanStrict();
+                }
+                catch (Exception ex)
+                {
+                    switch (ex)
+                    {
+                        case ArgumentException _:
+                        case FormatException _:
+                            jobContext.Warning($"Knob 'AGENT_DRAIN_QUEUES_AFTER_TASK' has wrong value, default value '{defaultDrainQueuesAfterTask}' will be set");
+                            break;
+                        default:
+                            throw;
+                    }
+                }
+
                 // trace out all steps
                 Trace.Info($"Total job steps: {jobSteps.Count}.");
                 Trace.Verbose($"Job steps: '{string.Join(", ", jobSteps.Select(x => x.DisplayName))}'");

src/Agent.Worker/StepsRunner.cs

@@ -310,7 +310,14 @@ namespace Microsoft.VisualStudio.Services.Agent.Worker
             step.ExecutionContext.Section(StringUtil.Loc("StepFinishing", step.DisplayName));
             step.ExecutionContext.Complete();
 
-            if (AgentKnobs.DrainQueuesAfterTask.GetValue(step.ExecutionContext).AsBoolean() == true)
+            bool drainQueuesAfterTask = AgentKnobs.DrainQueuesAfterTask.GetValue<BuiltInDefaultKnobSource>(step.ExecutionContext).AsBoolean();
+            try
+            {
+                drainQueuesAfterTask = AgentKnobs.DrainQueuesAfterTask.GetValue(step.ExecutionContext).AsBooleanStrict();
+            }
+            catch { }
+
+            if (drainQueuesAfterTask == true)
             {
                 try
                 {