Activity execution - .NET SDK

Start Activity Execution

Calls to spawn Activity Executions are written within a Workflow Definition. The call to spawn an Activity Execution generates the ScheduleActivityTask Command. This results in the set of three Activity Task related Events (ActivityTaskScheduled, ActivityTaskStarted, and ActivityTask[Closed])in your Workflow Execution Event History.

A single instance of the Activities implementation is shared across multiple simultaneous Activity invocations. Activity implementation code should be idempotent.

The values passed to Activities through invocation parameters or returned through a result value are recorded in the Execution history. The entire Execution history is transferred from the Temporal service to Workflow Workers when a Workflow state needs to recover. A large Execution history can thus adversely impact the performance of your Workflow.

Therefore, be mindful of the amount of data you transfer through Activity invocation parameters or Return Values. Otherwise, no additional limitations exist on Activity implementations.

To spawn an Activity Execution, use the ExecuteActivityAsync operation from within your Workflow Definition.

using Temporalio.Workflows;

[Workflow]
public class MyWorkflow
{
    public async Task<string> RunAsync(string name)
    {
        var param = MyActivityParams("Hello", name);
        return await Workflow.ExecuteActivityAsync(
            (MyActivities a) => a.MyActivity(param),
            new() { StartToCloseTimeout = TimeSpan.FromMinutes(5) });
    }
}

Activity Execution semantics rely on several parameters. The only required value that needs to be set is either a Schedule-To-Close Timeout or a Start-To-Close Timeout. These values are set in the Activity Options.

Get Activity Execution results

The Activity result is the returned in the task from the ExecuteActivityAsync call.