Summary:

Introduce the ability for Elsa 3 to maintain and track a history of workflow variable mutations.

Background:

Elsa currently supports defining and using workflow variables, but once an activity modifies a variable, the previous state/value of the variable is lost. For debugging, audit, and data analysis purposes, it would be invaluable to have a traceable history of how a variable has changed over time throughout the workflow execution.

Feature Description:

1. History Object: Whenever a workflow variable is mutated (e.g., updated, deleted), capture:

   • The previous value of the variable
   • The new value of the variable
   • The timestamp of mutation
   • The activity ID/name that initiated the mutation

2. Accessible via API: Expose an API endpoint that allows users to query the history of a variable by workflow instance or variable name.

3. UI Integration: In Elsa's dashboard, under each workflow instance, provide a section/tab dedicated to showcasing the history of variable mutations in a timeline or tabular format.

4. Configurability: Allow users to turn on/off this feature at the workflow or global level to cater to performance and storage considerations.

Use Case:

Consider a workflow where variable X starts with the value 10, is updated to 20 by Activity A, and then changed to 30 by Activity B. With this feature, a user can trace back the mutations, understanding which activity modified the variable and when.

Potential Benefits:

• Enhanced debugging: Easily trace back the sources of unexpected variable values.
• Auditing: Maintain a clear record of how data changes throughout the workflow execution.
• Data Analysis: Analyze patterns of data mutations for insights and improvements.

Would love to hear thoughts on the feasibility, and any additional requirements or concerns associated with implementing this feature.