Motivation

SRVCOM-1842 introduced support for domain-specific data correlation using context attributes for workflows which have event state as a start. However, there can be use cases when a workflow is not started using an event, rather using a plain HTTP request and an event state is "in the middle" of the workflow definition. This event state can wait just for a correlated event using a domain-specific data. This use case is currently not supported in the engine as in order to set the correlation values for the workflow instance when starting, the instance has to be started using a Cloud Event. Currently, the only correlation method for workflows started using an HTTP request is the workflow instance identifier.

Goal

Enable correlation values to be set also using an HTTP request, so workflows starting with e.g. an operation state can be correlated using domain-specific data as well.

Scenarios

As a developer, I need to start a workflow instance using an HTTP request and set its correlation values so when the instance reaches a waiting state (callback, event...) the instance can be correlated using a domain-specific data rather than just an instance identifier.

Expected outcomes

Correlation attributes values can be set also for workflows which don't start with event state. These correlation values are then available to event states during the workflow execution.

NOTE
Current Serverless Workflow specification v 0.8 does not present any examples for domain-specific data correlation in workflows without event state set as their start. At the same time, it does not forbid such a scenario. Therefore, this can be considered as a valid use case.