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Workflows4s Anatomy

What Does It Do?​

Workflows4s enables the creation of workflows using the WIO data type. A workflow built with WIO supports the following operations, as through the Workflow Elements:

  • Running side-effectful computations
  • Receiving signals from the external world
  • Querying workflow state at any time
  • Recovering workflow state without re-triggering side-effecting operations

WIO is a pure value object that describes the workflow. However, to execute it, you need a runtime capable of:

  • Persisting events in a journal
  • Reading events from the journal

How Does It Work?​

First Run​

  1. The workflow executes IOs along its path. Each IO produces an event that is persisted in the journal.
  2. Event handlers can modify the workflow state based on the events.
  3. The workflow halts execution when a signal or a timer is expected and resumes once the conditions are met.

Recovery (e.g., After a Service Restart)​

  1. Events are read from the journal and applied to the workflow.
  2. All previously executed IOs and received signals are skipped if corresponding events are already registered.
  3. Once all events are processed, the workflow continues execution as normal.