[PERF] Enhance Scalability and Simplify Workflow Execution with Proto.Actor

[sfmskywalker]

Objective

To improve the scalability and manageability of workflow execution, we propose refactoring the IWorkflowRuntime interface and fully adopting Proto.Actor as our primary execution runtime.

Current Challenges

• The existing IWorkflowRuntime interface is responsible for both workflow lookup and execution, leading to code duplication and complexity across its implementations (Default Runtime and ProtoActor Runtime).
• Managing distributed workflow instance cancellation is cumbersome, requiring complex orchestration and distributed messaging.

Proposed Changes

1. Decouple Workflow Matching and Execution:

   • Remove workflow matching responsibilities from IWorkflowRuntime.
   • Introduce a WorkflowMatcher service to handle finding workflows based on stimuli (renamed from "bookmark + trigger hashes").

2. Interface and Method Refinements:

   • Add a CreateWorkflowClient method to IWorkflowRuntime to return an IWorkflowClient, serving as a proxy to the workflow instance.
   • Transition to using Local Workflow Runtime and ProtoActor Workflow Runtime to reflect different operational contexts.

3. Terminology and Structural Adjustments:

   • Rename "bookmark + trigger payloads" to "stimuli" to clarify their role in triggering workflow actions in response to external input (stimuli).
   • Workflows can execute in "local context" (e.g. current HTTP context) and in "remote context" (e.g. Proto.Actor Workflow Runtime).
   • A workflow instance can transition from local context to remote context and vice versa through explicit operations that are yet to be defined.

4. Enhancements through Proto.Actor:

   • Lock-Free Execution: Utilize Proto.Actor’s capabilities for lock-free workflow execution, significantly increasing throughput.
   • Event Sourcing: Leverage Proto.Actor's event sourcing to ensure reliability and recoverability, reducing the need for the current WorkflowInboxMessages DB table.
   • Improved Pub/Sub: Leverage Proto.Actor for faster event broadcasting compared to traditional event buses.
   • Simplified Cancellation: Enable more straightforward cancellation of workflows via Proto.Actor, even during a burst of execution.
   • Performance Improvements: Maintain workflow state in memory within actors, allowing for quicker resumption and response to new stimuli.

Benefits

Adopting this refactoring will lead to a more scalable and efficient system with significantly simplified codebase and operational enhancements. The use of Proto.Actor will allow us to leverage advanced distributed system features, enhancing overall system responsiveness and reliability.

[sfmskywalker]

Tasks

• [ ] Update delivering workflow input before dispatching execution via MassTransit