Hi @Marvin, what are the options in prefect 3 that I want to setup automation for the flow to triiger a new run "after 10 seconds of previous flow run for the same flow"?

In Prefect 3.x, you can automate the scheduling of a flow run to trigger after a certain delay using Prefect's scheduling features. Prefect supports several types of schedules, such as Cron, Interval, and RRule, which you can define in a

prefect.yaml

file or through the Prefect CLI. To achieve your goal of triggering a new flow run 10 seconds after the previous run, you can use the Interval schedule. Here's a brief outline of how you might set this up: 1. Define an Interval Schedule: You can set up an interval schedule to run every 10 seconds. This can be done in the

prefect.yaml

file or through the Prefect CLI. 2. Deployment Configuration: When deploying your flow, specify this interval schedule. The deployment will then automatically handle triggering the flow at the specified intervals. Here's a snippet of what the relevant part of your

prefect.yaml

might look like:

yaml
schedules:
  - type: Interval
    interval: 10  # in seconds

For more detailed guidance, you can refer to the Prefect documentation on scheduling. If you want to manually control this logic in your flow using Python, you could introduce a delay at the end of your flow execution using something like

time.sleep(10)

before the flow completes. However, using Prefect's built-in scheduling is the recommended approach for automation. If you need any further help setting up your Prefect environment, feel free to ask!

Hi @Marvin, the interval is by the flow run start time or end time? For example, if the interval is 10 seconds, and the previous flow run takes 5 seconds, the next flow run will be 10 seconds after the previous flow run start, or 15 seconds after the previous flow run start?

In Prefect 3.x, an Interval schedule creates new flow runs at regular intervals, measured in seconds, starting from an optional

anchor_date

. The interval is calculated from the start time of the previous flow run. This means that if you set an interval of 10 seconds, the next flow run will start 10 seconds after the start of the previous run, not after it finishes. For more details on scheduling, you can refer to the Prefect documentation on scheduling.

Hi @Marvin, is there an easier way that I want to trigger a new flow run 10 seconds after the previous flow run ends?

To trigger a new flow run 10 seconds after the previous flow run ends, Prefect doesn't provide a built-in scheduling feature directly for this scenario. However, you can achieve this behavior by implementing a custom mechanism within your flow. Here's a general approach: 1. Use a Task to Trigger the Next Run: At the end of your flow, you can define a task that waits for 10 seconds and then triggers the next flow run. 2. Prefect Client: You can use the Prefect Client to programmatically trigger a new flow run after the delay. Here's a conceptual example:

python
from prefect import flow, task
import time
from prefect.client import get_client

@task
def wait_and_trigger_next_run(flow_id):
    time.sleep(10)  # Wait for 10 seconds
    client = get_client()
    client.create_flow_run(flow_id=flow_id)

@flow
def my_flow():
    # Your flow tasks here
    wait_and_trigger_next_run(flow_id="your-flow-id")

# Deploy and run your flow

This approach involves using a task at the end of your flow to introduce a delay and then using the Prefect Client to trigger the next flow run. You will need to replace

"your-flow-id"

with the actual ID of your flow. For more advanced scheduling and task handling, you might need to explore Prefect's capabilities further or consider additional orchestration logic outside of Prefect. For more information, you can refer to the Prefect documentation.

Hi @Marvin Is there a trigger template that I can use to detect "No running flow run for this flow"?

In Prefect 3.x, you can use custom triggers to detect the absence of events, such as when there are no running flow runs for a particular flow. This is done using a proactive trigger posture. Here's a general approach to achieve this: 1. Proactive Triggers: These triggers fire when a specified condition is not met within a defined window of time. For instance, you can set up a trigger to fire if a

prefect.flow-run.Running

event is not seen within a certain timeframe. 2. Trigger Configuration: You can configure this using Prefect's event-driven automation features. You'll need to define a trigger that checks for the absence of a

Running

state for your flow runs. Here's a conceptual example of what you might configure:

yaml
triggers:
  - type: proactive
    event: prefect.flow-run.Running
    within: 60  # seconds
    threshold: 0  # No running events
    actions:
      - type: notify
        message: "No running flow runs detected for the specified flow."

This configuration will notify you if no flow runs enter the

Running

state within the specified time window. For more details on setting up custom triggers, you can refer to the Prefect documentation on custom triggers.

Hi @Marvin, I used the

client.create_flow_run(flow_id=flow_id)

above but got error

PrefectClient.create_flow_run() got an unexpected keyword argument 'flow_id'

. Could you help me how to resolve it?

It seems there was a misunderstanding in the usage of

create_flow_run

in the Prefect Client. The

create_flow_run

method does not accept a

flow_id

argument directly. Instead, you should provide a deployment ID if you're creating a run for a specific deployment. Here's a corrected approach: 1. Use Deployment ID: Ensure you have the correct deployment ID for the flow you want to run. 2. Use the Correct Method: Use the

create_flow_run_from_deployment

method if you want to create a flow run from a deployment. Here's how you might use it:

python
from prefect.client import get_client

async def trigger_flow_run(deployment_id):
    async with get_client() as client:
        flow_run = await client.create_flow_run_from_deployment(deployment_id=deployment_id)
        print(f"Flow run created: {flow_run.id}")

# Example usage
deployment_id = "your-deployment-id"
trigger_flow_run(deployment_id)

Make sure to replace

"your-deployment-id"

with the actual deployment ID you are targeting. This method should correctly create a new flow run for the specified deployment.