Does anyone know if the local Prefect server is supposed to work with

DockerAgent

? I'm trying the example flow from the tutorial:

from prefect import Flow
from prefect import task
from prefect.run_configs import DockerRun


@task
def add(x, y=1):
    return x + y


with Flow("My first flow!", run_config=DockerRun()) as flow:
    first_result = add(1, y=2)
    second_result = add(x=first_result, y=100)

flow.register(project_name="test-project")

I submit the flow using the "Quick Run" button in the UI and start a Docker agent:

prefect agent docker start --show-flow-logs --log-level DEBUG

But the run forever stays in the pending state and I only ever see

Querying for flow runs / No flow runs found

in the agent logs. I've tried

DockerRun()

as above and also using a custom image containing only this:

FROM python:3.8-buster
RUN pip install prefect

The UI shows it can reach my agent, though. Any ideas?

Hi @Devin McCabe! What are your Flow labels?

Haven't applied labels anywhere yet

The flow can get a label from where it was registered from (and local agent gets the label by default as well). I think they might have matched that way by default.

Hmm, It seems a label was automatically applied when I registered the flow:

python pipeline/test.py
Flow URL: <http://localhost:8080/default/flow/ca78b43a-4077-462e-9634-e4248cc7def8>
 └── ID: 97fec098-4383-4a70-acd5-2133a1706e3b
 └── Project: test-project
 └── Labels: ['CA-dpm-hu']

That's my computer name. Where did that label come from?

That is applied by default on the Flow when you register and on the local agent when it starts.

None

must match with

None

to pick up the Flow.

Ah, I see. Thanks. I would think that

run prefect agent local start

and

run prefect agent docker start

would behave identically (aside from in the obvious way). The simplest possible LocalAgent+Flow example works only because the same magic label gets applied at both ends. Changing that recipe in a small way without reproducing that functionality breaks things. Kind of confusing.

I understand yeah. And

None

is a label in itself also. This is something we’re thinking about.. You can use the

--no-hostname-label

option for the local agent when spinning it up.