Execution context from Maestro on tasks and in handlers (4.5.0) — step 1

README.md

@@ -799,6 +799,19 @@ public class MyHandler : TaskRequestHandler<MyRequest, MyResponse>
 }
 ```
 
+#### Run context (Maestro)
+
+Maestro can start a workflow run with an execution context: key/value pairs such as the tenant
+and user the run is for. It sends the context with every polled task, and the workflow cannot
+change it, so read identity from there rather than from the task input:
+
+```csharp
+var workspaceId = _context.Context.TryGetValue("workspaceId", out var id) ? id : null;
+```
+
+Set it when starting a run with `StartWorkflowRequest.Context`. Conductor sends no context, so
+against Conductor `Context` is empty and the field is left out of start requests.
+
 ## Patterns Package
 
 Additional built-in tasks and utilities:

src/ConductorSharp.Client/ConductorSharp.Client.csproj

@@ -6,7 +6,7 @@
 		<Authors>Codaxy</Authors>
 		<Company>Codaxy</Company>
 		<PackageId>ConductorSharp.Client</PackageId>
-		<Version>4.4.1</Version>
+		<Version>4.5.0</Version>
 		<Description>Client library for Netflix Conductor, with some additional quality of life features.</Description>
 		<RepositoryUrl>https://github.com/codaxy/conductor-sharp</RepositoryUrl>
 		<PackageTags>netflix;conductor</PackageTags>

src/ConductorSharp.Client/Generated/ExecutionContext.cs

@@ -0,0 +1,40 @@
+using Newtonsoft.Json;
+
+namespace ConductorSharp.Client.Generated
+{
+    // The execution context is a Maestro extension of the Conductor API: key/value pairs a workflow
+    // run is started with, kept unchanged for the life of the run and inherited by its sub-workflows.
+    // Conductor neither sends nor reads it. These partials live outside Models.cs so regenerating the
+    // models does not drop them.
+
+    public partial class Task
+    {
+        /// <summary>
+        /// Execution context of the workflow run this task belongs to, as Maestro sends it with a
+        /// polled task. Null from Conductor.
+        /// </summary>
+        [JsonProperty("context", Required = Required.Default, NullValueHandling = NullValueHandling.Ignore)]
+        public IDictionary<string, string>? Context { get; set; }
+    }
+
+    public partial class Workflow
+    {
+        /// <summary>
+        /// Execution context the run was started with, as Maestro reports it on a workflow read.
+        /// Null from Conductor.
+        /// </summary>
+        [JsonProperty("context", Required = Required.Default, NullValueHandling = NullValueHandling.Ignore)]
+        public IDictionary<string, string>? Context { get; set; }
+    }
+
+    public partial class StartWorkflowRequest
+    {
+        /// <summary>
+        /// Execution context to start the run with. Maestro stores it with the run, hands it to every
+        /// task and sub-workflow, and never lets the workflow change it. Omitted from the request when
+        /// null, so a start against Conductor is unchanged.
+        /// </summary>
+        [JsonProperty("context", Required = Required.Default, NullValueHandling = NullValueHandling.Ignore)]
+        public IDictionary<string, string>? Context { get; set; }
+    }
+}

src/ConductorSharp.Engine/ConductorSharp.Engine.csproj

@@ -6,7 +6,7 @@
     <Authors>Codaxy</Authors>
 	<Company>Codaxy</Company>
 	<PackageId>ConductorSharp.Engine</PackageId>
-	<Version>4.4.1</Version>
+	<Version>4.5.0</Version>
     <Description>Client library for Netflix Conductor, with some additional quality of life features.</Description>
 	<RepositoryUrl>https://github.com/codaxy/conductor-sharp</RepositoryUrl>
 	<PackageTags>netflix;conductor</PackageTags>

src/ConductorSharp.Engine/ExecutionManager.cs

@@ -145,6 +145,12 @@ private async Task PollAndHandle(TaskToWorker scheduledWorker, CancellationToken
                 return;
             }
 
+            // A transport other than HTTP may answer "no task" with null instead of a 204, as
+            // Maestro's in-process transport does. Handling it here keeps that from surfacing as a
+            // NullReferenceException in a poll nobody awaits.
+            if (pollResponse == null)
+                return;
+
             await ProcessPolledTask(pollResponse, workerId, scheduledWorker, cancellationToken);
         }
 
@@ -200,6 +206,7 @@ CancellationToken cancellationToken
                     context.TaskReferenceName = pollResponse.ReferenceTaskName;
                     context.WorkflowId = pollResponse.WorkflowInstanceId;
                     context.CorrelationId = pollResponse.CorrelationId;
+                    context.Context = ConductorSharpExecutionContext.CopyContext(pollResponse.Context);
                     context.TaskId = pollResponse.TaskId;
                     context.WorkerId = workerId;
                 }

src/ConductorSharp.Engine/TypePollSpreadingExecutionManager.cs

@@ -154,6 +154,12 @@ private async Task PollAndHandle(TaskToWorker scheduledWorker, CancellationToken
                 return;
             }
 
+            // A transport other than HTTP may answer "no task" with null instead of a 204, as
+            // Maestro's in-process transport does. Handling it here keeps that from surfacing as a
+            // NullReferenceException in a poll nobody awaits.
+            if (pollResponse == null)
+                return;
+
             await ProcessPolledTask(pollResponse, workerId, scheduledWorker, cancellationToken);
         }
 
@@ -209,6 +215,7 @@ CancellationToken cancellationToken
                     context.TaskReferenceName = pollResponse.ReferenceTaskName;
                     context.WorkflowId = pollResponse.WorkflowInstanceId;
                     context.CorrelationId = pollResponse.CorrelationId;
+                    context.Context = ConductorSharpExecutionContext.CopyContext(pollResponse.Context);
                     context.TaskId = pollResponse.TaskId;
                     context.WorkerId = workerId;
                 }

src/ConductorSharp.Engine/Util/ConductorSharpExecutionContext.cs

@@ -1,17 +1,46 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Text;
 
 namespace ConductorSharp.Engine.Util
 {
     public class ConductorSharpExecutionContext
     {
+        private static readonly IReadOnlyDictionary<string, string> NoContext = new ReadOnlyDictionary<string, string>(
+            new Dictionary<string, string>()
+        );
+
         public string WorkflowName { get; set; }
         public string WorkflowId { get; set; }
         public string TaskName { get; set; }
         public string TaskId { get; set; }
         public string TaskReferenceName { get; set; }
         public string CorrelationId { get; set; }
         public string WorkerId { get; set; }
+
+        /// <summary>
+        /// The execution context of the workflow run the task belongs to: key/value pairs the run was
+        /// started with, such as the tenant and user it runs for. Maestro sends it with every polled
+        /// task. Conductor sends none, and then this is empty.
+        /// </summary>
+        /// <remarks>
+        /// Read identity from here rather than from the task's input. Maestro does not let the
+        /// workflow change the context after the start, while the input is whatever the workflow
+        /// definition puts there.
+        /// </remarks>
+        public IReadOnlyDictionary<string, string> Context { get; set; } = NoContext;
+
+        /// <summary>
+        /// Copies the context from a polled task, so a handler cannot change what the next handler
+        /// sees by writing to the task's dictionary.
+        /// </summary>
+        internal static IReadOnlyDictionary<string, string> CopyContext(IDictionary<string, string> context)
+        {
+            if (context == null || context.Count == 0)
+                return NoContext;
+
+            return new ReadOnlyDictionary<string, string>(new Dictionary<string, string>(context));
+        }
     }
 }

src/ConductorSharp.KafkaCancellationNotifier/ConductorSharp.KafkaCancellationNotifier.csproj

@@ -4,7 +4,7 @@
     <TargetFramework>net6.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <Version>4.4.1</Version>
+    <Version>4.5.0</Version>
     <Authors>Codaxy</Authors>
     <Company>Codaxy</Company>
   </PropertyGroup>

src/ConductorSharp.Patterns/ConductorSharp.Patterns.csproj

@@ -7,7 +7,7 @@
     <GeneratePackageOnBuild>False</GeneratePackageOnBuild>
     <Authors>Codaxy</Authors>
     <Company>Codaxy</Company>
-    <Version>4.4.1</Version>
+    <Version>4.5.0</Version>
   </PropertyGroup>
 
 	<ItemGroup>

src/ConductorSharp.Toolkit/ConductorSharp.Toolkit.csproj

@@ -7,7 +7,7 @@
     <Nullable>disable</Nullable>
 	<PackAsTool>true</PackAsTool>
 	<ToolCommandName>dotnet-conductorsharp</ToolCommandName>
-	<Version>4.4.1</Version>
+	<Version>4.5.0</Version>
   </PropertyGroup>
 
   <ItemGroup>