How to add edit the CronSchedule with python script (instead of webui)?

[mr-tester-william-lo]

Currently, i have this code:

from prefect import Flow
from prefect.schedules import CronSchedule
from prefect.tasks.prefect import StartFlowRun
from datetime import datetime

weekday_schedule = CronSchedule(
    "30 * * * 2-3", start_date=datetime.now()
)

flow_1 = StartFlowRun(
                flow_name="this_is_a_flowname", 
                project_name="this_is_a_projname",
                parameters={ "Task1_Var": "11111", "Task2_Var": "22222" },
                wait=True
                )
with Flow("parent-flow", schedule=weekday_schedule) as flow:
    flow_1
flow.register( project_name = "testing" )

This workflow has been registered in prefect server/cloud. I found the web-UI can edit the schedule, but i cannot find any related package in python which allows me to add/remove/edit the CronSchedule or change to another schedule package "IntervalSchedule". So, how can I do it in python?

Note that I prefer I can set my schedule out of my flow code with the use of python.

[kvnkho]

Hi @mr-tester-william-lo ,

I am not understanding 100% so I'll just try to answer as best I can.

First, I just want to make sure you know that you can combine CronClocks and IntervalClocks to make a more complex schedule. You can do something like:

clock1   = clocks.IntervalClock(...)
clock2   = clocks.CronClock(...)

# the full schedule
schedule = Schedule(clocks=[clock1, clock2])

From my understanding, your Flow has a CronSchedule and you want to change to IntervalSchedule. All you need to do is change your weekday_schedule to the IntervalSchedule and re-register the flow for it to take effect.

schedule = IntervalSchedule(interval=timedelta(minutes=2))

with Flow("parent-flow", schedule=schedule) as flow:
    flow_1
flow.register( project_name = "testing" )

This will replace the schedule for you.

Now on the last bit, you want to set the schedule outside of Flow code. You can do something like this from another file:

from prefect.utilities.storage import extract_flow_from_file

def register_flow(file, project, labels):
    file_path = os.path.abspath(file)
    flow = extract_flow_from_file(file_path=file_path)
    flow.schedule = IntervalSchedule(interval=timedelta(minutes=2))
    flow.register(project_name=project, labels=labels, no_url=True)

I don't recommend this though because setting Executor and Results this way will not work. Those need to be defined in the script where you have the Flow. This will work for schedules though. And then as you mentioned, the UI is also another way to edit schedules of registered flows.

What is your use case that you need the schedule detached from the Flow code?

[kvnkho]

Sorry for the slight delay.

I get what you're saying now. Yes you can use the GraphQL API to set schedules on Flows. There is a set_flow_group_schedule that you can use like this:

from prefect.client.client import Client

client = Client()

query = """
mutation {
  set_flow_group_schedule (input: {
      flow_group_id: "795512b7-c9f7-4231-8d6b-c80dbd87231d", 
      cron_clocks: [{cron: "0 9 * * *", parameter_defaults: "{\\"x\\": 1}"}]}) {
    success
    error
  }
}
"""
client.graphql(query)

Note that cron_clocks takes in multiple clocks here with multiple parameters. This mutation also takes in interval clocks, you can find more details in the Interactive API tab of the UI. To delete existing schedules from Flows is a similar mutation.

mutation {
  delete_flow_group_schedule (input: {flow_group_id: "d3a03515-8876-4564-aa45-382b394110a3"}) {
    success
    error
  }
}

[mr-tester-william-lo]

Thanks, problem solved. Not much information in the documentation.
Below link find more Graphql Query Method
https://github.com/PrefectHQ/prefect/tree/master/docs/orchestration/concepts

[mr-tester-william-lo]

May I know how to add labels to the schedule created by graphql?

i can only find this:

prefect/src/prefect/schedules/clocks.py

Line 255 in d61fa6a

labels: List[str] = None,

, but it is not related to graphql query

[zhen0]

Hi @mr-tester-william-lo - thanks for the question.

Labels aren't currently exposed as an input for the set_flow_group_schedule graphQL mutation. The code you are referencing is for setting a flow in code (where you can add labels as part of a cron_clock).

You can add labels separately using the set_flow_group_labels mutation but that will affect all flow runs, not just the ones created by a certain schedule.

If you'd like to be able to set labels for a schedule through the graphQL API I suggest you open an issue so we can look into it.

Also if you need documentation for what you can do using the graphQL API, take a look at the Interactive API in the web UI. It has a docs section listing the graphQL API schema.

[mr-tester-william-lo]

if

• I have 2 agents, one is agent1 from cluster1 and another one is agent2 from cluster 2,
• They share the same code in prefect workflow but different parameters,
• the prefect workflow label as (label1, label2), agent1 label as (label1) and agent2 label as (label2)

Then, do you mean:

• i have no choice to schedule and run them in the corresponding cluster if I do not hard code the schedule in the workflow?

Note that in above test case, both agents will be triggered by the schedule run.