A C#.NET library, built on Amazon SWF ( Simple Workflow Service ), lets you coordinate the execution of serverless AWS Lambda functions, activities, child workflows and timers with ease.

 Install-Package Guflow
     OR
 dotnet add package Guflow

Guflow provides high level and easy to use APIs to program Amazon SWF. In Guflow you can write-

• Workflows to orchestrate the scheduling of AWS lambda functions, activities, child workflows and timers
• Activities to carry out the task.

Guflow, supporting all the relevant features of Amazon SWF, is an alternative to Amazon Step functions and the Amazon Flow framework and it provides simplicity and flexbility in one place.

Guflow:

• Allows you to create complex workflows with ease and flexibility
• Use async task for polling for new decisions and activity tasks
• Provide equal supports for scheduling the activities written in other framework/language
• Supports async/sync activity method
• Supports activity throttling
• Supports parallel execution of lambda, activities and timers in workflow
• Supports fork and join of workflow branches
• Supports loop around an individual item(lambda, activity, child workflow and timer) or whole execution branch
• Supported by behavioural unit tests and continuously released.
• Supports all the relevant features of Amazon SWF:
  • Lambda
  • Activity
  • Timer
  • Child workflows
  • Signal
  • Workflow/child-workflow cancellation
  • Marker
  • Activity heartbeat and cancellation
  • Handling of all error events.

Following example shows BookHolidays workflow using AwsLambda:

        BookFlight          BookHotel
            |                   |
            |                   |
            v                   v
        ChoosSeat          BookDinner
            |                   |
            |                   |
            `````````````````````
                    |
                    v
              ChargeCustomer
                    |
                    v
               SendEmail
              
    [WorkflowDescription("1.0")]
    public class BookHolidaysWorkflow : Workflow
    {
        public BookHolidaysWorkflow()
        {
            ScheduleLambda("BookFlight").When(_=>Input.BookFlight);
            ScheduleLambda("ChooseSeat").AfterLambda("BookFlight");

            ScheduleLambda("BookHotel").When(_ => Input.BookHotel);
            ScheduleLambda("BookDinner").AfterLambda("BookHotel");

            ScheduleLambda("ChargeCustomer").AfterLambda("ChooseSeat").AfterLambda("BookDinner");
            
            ScheduleLambda("SendEmail").AfterLambda("ChargeCustomer");
        }
        [WorkflowEvent(EventName.WorkflowStarted)]
        private WorkflowAction OnStart()
        {
            if (!Input.BookFlight && !Input.BookHotel)
                return CompleteWorkflow("Nothing to do");

            return StartWorkflow();
        }
    }             
          

Above workflow has four possible execution scenarios:

• 1. User has choosen to book both flight and hotel: In this case two branches "BookFlight->ChoosSeat" and "BookHotel->BookDinner" will schedule in parallel and ChargeCustomer lambda function will be scheduled only after completion of ChooseSeat and BookDinner lambda functions.
• 2. User has choosen to book the flight only: In this case ChargeCustomer lambda will be scheduled after ChooseSeat lambda.
• 3. User has choosen to book the hotel only: In this case ChargeCustomer lambda will be scheduled after BookDinner lambda.
• 4. User has choosen not to book flight or hotel: Workflow will be completed immediately.

You can implement the above workflow using SWF activities with same ease. You can also mix activities, lambdas or timers in a workflow.

To understand the scheduling of lambda functions, activities, child workflows and timers in a workflow, please read about Delflow algorithm and workflow branches. Default implementation will good enough for majority of complex scenarios, however you have flexibility to customize every aspect of it.

You can find details about all supported workflow actions here.

Features in pipeline: Please look at project board to see what is is coming next. If you want some feature to be included in Guflow library or something is not working for you please file an issue. Your ideas, suggestion and collorbation will greatly help this library and its users.

Guflow is supported by tutorial, documentation and samples to get you started easily.

dotnet standard 1.3 onwards

Please raise issue in github