2.1.7

flyteplugins.hitl

Human-in-the-Loop (HITL) plugin for Flyte.

This plugin provides an event-based API for pausing workflows and waiting for human input.

Basic usage: 

import flyte
import flyteplugins.hitl as hitl

task_env = flyte.TaskEnvironment(
    name="my-hitl-workflow",
    image=flyte.Image.from_debian_base(python_version=(3, 12)),
    resources=flyte.Resources(cpu=1, memory="512Mi"),
    depends_on=[hitl.env],
)


@task_env.task(report=True)
async def main() -> int:
    # Create an event (this serves the app if not already running)
    event = await hitl.new_event.aio(
        "integer_input_event",
        data_type=int,
        scope="run",
        prompt="What should I add to x?",
    )
    y = await event.wait.aio()
    return y

Features:

  • Event-based API for human-in-the-loop workflows
  • Web form for human input
  • Programmatic API for automated input
  • Support for int, float, str, and bool data types
  • Crash-resilient polling with object storage

Directory

Classes

Class Description
Event An event that waits for human input via an embedded FastAPI app.

Methods

Method Description
new_event() Create a new human-in-the-loop event.

Variables

Property Type Description
env TaskEnvironment

Methods

new_event()

This method can be called both synchronously or asynchronously.

Default invocation is sync and will block. To call it asynchronously, use the function .aio() on the method name itself, e.g.,: result = await new_event.aio().

 
def new_event(
    name: str,
    data_type: Type[T],
    scope: EventScope,
    prompt: str,
    timeout_seconds: int,
    poll_interval_seconds: int,
) -> Event[T]

Create a new human-in-the-loop event.

This is a convenience function that wraps Event.create().

Parameter Type Description
name str A descriptive name for the event (used in logs and UI)
data_type Type[T] The expected type of the input (int, float, str, bool)
scope EventScope The scope of the event. Currently only “run” is supported.
prompt str The prompt to display to the human
timeout_seconds int Maximum time to wait for human input (default: 1 hour)
poll_interval_seconds int How often to check for a response (default: 5 seconds)

Returns

An Event object that can be used to wait for the human input