Tasks Overview

In this section, we delve into the specifics of the task executor's implementation.

A basic task implementation would appear as follows:

@CommandModel("example-task")
export class ExampleCommand extends TaskCommand {
    @ApiProperty()
    @IsString()
    public name: string
}

@ResponseModel("example-task")
export class ExampleResponse extends TaskResult {
    @ApiProperty()
    @IsString()
    public result: string
}

@Executor("example-task")
export class ExampleExecutor implements TaskExecutor {

    async processTask(exampleCommand: ExampleCommand): Promise<ExampleResponse> {
        return {
            result: `Hello ${exampleCommand.name} !!! `
        }
    }
}

decorator::@Executor

Marks the class as an executor of the task.

@Executor('example-task')

• Parameters:
  • name: string - The name of the task

@Executor('example-1')
export class ExampleExecutor implements TaskExecutor {
    async processTask(command: ExampleCommand): Promise<ExampleResponse> {
        // shared implementation for all aliases
    }
}

Task Status

A task can be in one of the following states:

Value	When
ACCEPTED	Task has been received and queued, but has not started running yet.
IN_PROGRESS	Task is running. Appears on polled results between partial-result/progress emissions and the final response.
COMPLETED	Task finished successfully. The result field is populated.
FAILED	Task threw an error. The result field carries the ErrorResult (reason, message, statusCode, details).

interface::TaskExecutor

Tasks decorated as an executor should implement processTask method of TaskExecutor interface. Once a new task execution request is submitted the method will be called with the following params

• command: Any - the input payload of the task passed in the request
• meta: TaskMetadata - meta information about the task. The object can be used to identify the user, user's subscription plan and other info about request context.

@Executor("example-task")
export class ExampleExecutor implements TaskExecutor {
    async processTask(command: ExampleCommand, metadata: TaskMetadata, flow: Flow): Promise<ExampleResponse> {
        const userId = flow.meta().userId();
        return {
            result: `Hello ${command.name}`
        };
    }
}

note

metadata: TaskMetadata is deprecated — prefer flow.meta() for new code. See the full surface, including the caller's subscription tier, in Flow Metadata.

@CommandModel("example-task")

Marks the class as input payload model for a given task

• name: string - The name of the task

To apply validation on task input payload you can add decorators from class-validator on model properties

@CommandModel("example-task")
export class ExampleCommand extends TaskCommand {
    @ApiProperty()
    @IsString()
    public name: string
}

@ResponseModel("example-task")

Marks the class as output payload model for a given task

• name: string - The name of the task

@ResponseModel(Commands.EXAMPLE)
export class ExampleResponse extends TaskResult {
    @ApiProperty()
    @IsString()
    public result: string
}

naming convention

To maintain consistency please keep naming convention of the classes.

• Task Executor class name should end with Executor

• Task input model name should end with Command

• Task output model name should end with Response

• Response result nested model (if any) name should end with Result