Definition

A transaction method is a method on a step class annotated with the @transaction decorator, imported from ansys.saf.glow.solution. When annotated, the method is automatically exposed as an endpoint in the solution REST API and can be called from the application UI or any Python client.

The @transaction decorator

The @transaction decorator is the core mechanism for defining transaction methods. It accepts arguments that control which step fields the method reads from and writes to:

from ansys.saf.glow.solution import StepModel, transaction


class MyStep(StepModel):
    input_value: float = 0.0
    result: float = 0.0

    @transaction(
        self=["input_value"],
        output=["result"],
    )
    def compute(self) -> None:
        self.result = self.input_value * 2.0

In the example above:

• self lists the fields that are fetched from the persisted step state before the method runs.

• output lists the fields that are written back to the persisted step state after the method completes.

Fetching and modifying step fields

Transaction methods can read and update persisted step data. The decorator arguments define which fields are loaded into memory before the method executes and which are saved back to the database after it returns. This mechanism also establishes dependencies between fields, so that downstream fields are automatically invalidated when their upstream inputs change.

REST API exposure

Each transaction method is automatically registered as a REST API endpoint by SAF GLOW Engine. This means that the method can be invoked:

• From the Dash frontend using the DashClient.

• From a Python script using the solution’s REST API directly.

• From any other HTTP client that can authenticate with the solution.

Cloud compatibility

The implementation of transaction methods is designed to support both cloud and on-premises deployments. See Cloud compatibility for guidelines on writing transaction methods that work correctly in distributed environments.

Note

Child processes started by a transaction method are automatically terminated when the method completes, regardless of whether the method succeeds or raises an exception.