Hi, I have os.path.join(path, folder) in my task, and I can run flow with it from python script but not on prefect UI. The error message is: Unexpected error: TypeError('expected str, bytes or os.PathLike object, not NoneType',). Anyone has any thoughts? Thanks in advance.

Hey! Welcome to the Prefect Slack channel. Could you share the flow script?

with Flow(“fv_grid_flow”) as flow:     path = Parameter(“inputs”, required=True)     read_file(path)

Oh I see. In this case, are you passing the value when you trigger from the UI since there is no default value here?

so you are saying UI won't read json but instead i need to type the parameters on UI?

No no. I’m saying that if you have

test = Parameter("test", required=True)

if you go to the UI, you have to supply a value to

test

because there is no default value set. But if you do:

test = Parameter("test", default=1)

then you don’t need to supply in the UI because it can use the default. So it looks like the error is saying that the parameter is

None

? This is what making me wonder if there is a value supplied Also, can I see the definition of

read_file

? Is that a task?

yes, it's a task. so i can supply a default value on UI, but it will still read parameters from json file?

If you supply the path to that Parameter, yes this should work because the

read_file

task will read in the json file

you are right about this, it solved the problem. thanks a lot!

Of course!

hi another error also only on UI, [WinError 2] The system cannot find the file specified, any thoughts?

Are you using Local agent?

yes

So the agent starts the Flow as a Python process in the same working directory. Maybe you need to specify the right working directory so that it can load the things it needs? There is an example of configuring that here .

yes, i am running in the same machine

Ok I think you just need to start the agent in the right location or use the

LocalRun

to specify the working directory

With set_temporary_config(get_server_config(server, port)):    LocalAgent(import_paths=python_path).start()

Wait, no. The labels are correct in that they are the way to specify which machine to start on. But the

working_dir

should be defined on the Flow side. In you flow,

from prefect.run_configs import LocalRun

tasks....

with Flow(...) as flow:
    tasks....

flow.run_config = LocalRun(working_dir="/path/to/working-directory")

and then register this. When the agent picks up this Flow, it will run the Flow in that working directory. I think this should help you locate the files on the machine.

i did what you suggested about run_config, i think the run stuck somewhere, i see the status "scheduled", but not "submitted"

Oh I see if it’s scheduled but not submitted. That is a labelling issue most of the time. What are the labels for your flow and agent?

hostname=socket.gethostname() labels=[hostname] flow.environment = LocalEnvironment(executor=executor, labels=labels)

Environments are deprecated and they were replaced the RunConfigs so you shouldn’t use LocalEnvironment. You want RunConfiguration instead, specifically the LocalRun to pair with Local Agent. The agent would need the flow label with the machine name to be able to pick up the flow. If you start the agent with the CLI command:

prefect agent local start

The agent will have the hostname by default also. You can also remove the label from the Flow but for LocalAgent, it would be good to have labels on both Flow and agent

i see, let me take a look

can you show be the flow code?

with Flow(...) as flow:
    ....

sure, bear with me for a sec, my code is in another remote machine, i have to type them in this chat, the v is 0.13.19

no worries

With Flow(“fv_grid_flow”) as flow:   Inputs = Parameter(“inputs”, required = True)   batchName, xmlPath, config_file, grid_config = _prepare_requests(inputs)   mapped_results = _grid_client.map(batchName, xmlPath, unmapped(config_file), unmapped(grid_config))

can i see the __grid__client definition?

it's a long piece of code, but essentially, it's calling an in-house function of gridclientscenario analysis

Is your code calling the query? What are you trying to do with the query?

that's prefect calling the query

Can you try not mapping but passing all 4

batch_name

,

xml_path

,

xml_config_file

,

grid_config

?

yeah, i tried with this, mapped_results = _grid_client(batchName[0], xmlPath[0], config_file, grid_config), and it worked

@E Li can you share what Prefect version do you use in the environment from which you registered this flow, and which Prefect version runs on this agent? This may be a version mismatch according to this: https://github.com/PrefectHQ/prefect/issues/4640

the are all 0.13.19, i actually had to downgrade my prefect to match what's running on the agent

Are you using local agent?

yes

Thanks for confirming that. But this error really looks the same as in the Github issue 🤔 and there it was the version mismatch. Could you perhaps test this flow with a local agent based on the latest version 0.15.7, and use also 0.15.7 during registration and check if the error happens again? You could create a new agent in your terminal using:

prefect agent local start

yep, let me do that

Are you on server or Cloud?

in the meanwhile, attached log for additional info

ohh it looks like it’s your server version that needs to be upgraded i think

ok, how should i do that upgrade?

You can find the instructions here .

yeah, i don't think i can register with 0.15.7 to a server with lower version

you can’t but i think when you were on 0.13.19, I think your server was an even lower version

right

Yeah using the graphql api. Let me look

it works, thank you