CommandR: Diagrams

Diagrams for the CommandR concepts introduced in Part 4.

Command Handler Pipeline

Handler	Priority	Type	Purpose
PreparedCommandHandler	1,000,000,000	Filter	Calls IPreparedCommand.Prepare() if implemented
CommandTracer	998,000,000	Filter	Creates Activity for tracing, logs errors
LocalCommandRunner	900,000,000	Filter	Runs ILocalCommand.Run() if implemented
RpcCommandHandler	800,000,000	Filter	Routes to RPC if command should be handled remotely
OperationReprocessor	100,000	Filter	Operations Framework
NestedOperationLogger	11,000	Filter	Operations Framework
OperationScopeProvider	10,000	Filter	Operations Framework
DbOperationScopeProvider	1,000	Filter	Operations Framework
Your Handler	0	Final	Your business logic

CommandContext Hierarchy for Nested Commands

Property	Behavior
ServiceScope	Shared across all nested contexts (same ICommander)
Items	Each context has its own dictionary
OutermostContext	Always points to the root context
Data sharing	Use context.OutermostContext.Items to share across contexts

IOutermostCommand Behavior

IDelegatingCommand Behavior

Code in CommandContext.New():

if (!isOutermost && (command is IOutermostCommand ||
                     Current?.UntypedCommand is IDelegatingCommand))
    isOutermost = true;

IEventCommand Parallel Execution

Scenario	Behavior
ChainId is empty	RunEvent() builds chains, clones command for each, runs in parallel
ChainId is set	Goes through RunCommand(), executes only that specific handler chain

ChainId format: {ServiceType.GetName()}.{Method.Name}

ISessionCommand Processing (RpcDefaultSessionReplacer)

RpcDefaultSessionReplacer Logic

Step	Action
1	Check if first param is ISessionCommand
2	Get SessionBoundRpcConnection from peer
3	If session.IsDefault(): command.SetSession(connection.Session)
4	Else: session.RequireValid()

Session Resolution Flow

Handler Registration and Resolution

Registration (at startup)

Resolution (at runtime)

Index	Handler	Priority	Type
[0]	PreparedCommandHandler	1,000,000,000	Filter
[1]	CommandTracer	998,000,000	Filter
[2]	LocalCommandRunner	900,000,000	Filter
[3]	RpcCommandHandler	800,000,000	Filter
[4]	OperationReprocessor	100,000	Filter
[5]	NestedOperationLogger	11,000	Filter
[6]	InMemoryOperationScope	10,000	Filter
[7]	DbOperationScopeProvider	1,000	Filter
[8]	YourHandler	0	Final

Command Service Proxy (AOP)

Call Style	Result
commander.Call(new CreateOrderCommand(...), ct)	Full pipeline
orderService.CreateOrder(new CreateOrderCommand(...), ct)	Full pipeline (via proxy)

Both paths go through: PreparedCommandHandler → CommandTracer → ... → Handler