Probably a stupid question: how do I get the value of a

Parameter

. My use case is building a shell command:

data_source_id = Parameter("data_source_id")
# ...
t = shell_task(command=f"some_script {data_source_id}")

Are there plans to have an async executor? When mapping over a list of IO blocking tasks, it'd be nice to spawn them off in an event loop rather than threads or processes.

Hello again, all! I'm probably missing something, but when I'm trying to run simple mapping example through agent, it won't finish. This is the flow definition:

from prefect import Flow, task

@task
def add_ten(x):
    return x + 10

with Flow('simple map') as flow:
    mapped_result = add_ten.map([1, 2])

flow.register()
flow.run_agent()

When running the flow from UI, the task "add_ten (Parent)" is stuck in state "Mapped" (with description "Preparing to submit 2 mapped tasks"). What's wrong?

Hi ! I am very curious and eager to use the new open-source ui. I tried the example on the blog post and now I am wondering how our code base can adapt to use it. My main confusion today is where does a DaskScheduler and their related workers fit on this? We have a kubernetes cluster with one dask scheduler a horizontal pod scaler for the workers, and several cronjobs to trigger jobs. Last time I went deep into prefect, there were no agents (or at least I don’t remember them), so I guess that agents and flow configuration can replace cronjobs on my side, but I don’t see where workers fit in now.

Hi, I am playing with the local UI server. Is there away to specify to the agent the IP of the server to connect to? prefect backend server --help Usage: prefect backend [OPTIONS] API Switch Prefect API backend to either

server

or

cloud

Options: -h, --help Show this message and exit.

The prefect backend does seem to accept IP for a remote server

I have started using the PostgresExecutor task and after reading the source and trying to understand how it works, I'm not clear on transactions and exactly how lots of separate tasks get rolled into them.. (https://github.com/PrefectHQ/prefect/blob/master/src/prefect/tasks/postgres/postgres.py#L174-L203)

Is there an easy way to run part of a flow? I.e. run up to and including task

x

?

hi, I'm considering using prefect both for a short term need and a longer term project

I was attempting to solve some automation problems related to standing up a hypervisor, putting vms on it, and configuring those VMs

I was using ansible for this, but increasingly became frustrated with it (it seemed to be getting in the way rather than helping)

what do people who have used prefect think about using it for automation of these kinds of tasks?

is there anything builtin for making shell execution and ssh execution more convenient, or would I just leverage the best I can find in terms of python libraries for that?

I have a data structure question that I couldn't clearly resolve from your docs

do you have an idiom for running flows within flows?

Hi Prefect Team, we are evaluating a few workflow solutions at my workplace and have a few questions on perfect that I think might get answered on this slack channel. 1. Do you guys have an estimate of the level of effort needed for some current airflow users to migrate to prefect? If you have specific real world examples, it would be great. 2. I have read Prefect is pretty fast and real-time. Do you have some metrics around it for comparison or to look at the numbers? I believe we will have information on what kind of workflows were used to derive these metrics. 3. How do prefect core users handle state management (specifically storing / managing dag state) today? Are there any examples for us to look at? 4. We tried searching for but did not come across any video tutorials of Prefect. My team is fond of video tutorials:) so checking if there are any available on the internet already that I might have not looked at. Please share any links that might address the above questions. Thank you so much!

Has anyone else had issues with VSCode not picking up

prefect

typing information when importing the module?

mypy

is also complaining…

the usage of this community seems like it would fit better with a discourse forum, allowing tagging and searching. so many posts with detailed discussion and i can't really discover relevant posts, discern between novice/expert questions, or search for questions i may also have.

Hello 👋, I register my flow to the cloud and start the agent directly from a python process. The flow is directly build in a docker container by my own. However, at each build and new invocation, a different agent is spinning up in the cloud UI. How can I tell the UI it's the same one which have disconnected and then reconnected?

And another complete different question 🙋 I have set up the LocalDaskExecutor (via the env variable) and my flow is run by the cloud. However, tasks are run one by one. How can I achieve parallelism and run more than one in parallel?

set the channel topic: Welcome to the Prefect community! Please use threads if possible so we can archive helpful conversations to our GitHub knowledge base: https://github.com/PrefectHQ/prefect/issues?q=label%3A%22Prefect+Slack+Community%22+

Have observed a significant difference in overall execution time between running a flow manually and running the same flow via a local agent on the same machine (triggered via prefect cloud). Consistently 20-25 times slower for this particular flow (lots of mapped tasks). Expected behaviour?

Hi guys, quick question - I would like to run a task conditioned by an optional

Parameter

. Which construct should I use?

ifelse

doesn't seem fit for this, since I don't have another task for the false condition. In airflow it was solved using a

DummyOperator

and it always looked somewhat redundant. Is there an idiomatic way with Prefect? UPDATE: nevermind, just read about the SKIP signal 🙂

Hi all, first of all thanks for what looks like a great product so far! I'm trying to use the core server to submit jobs to the docker agent. I can register flows ok and when I run them they are picked up by the agent. But they sit at 'submitted'. Looking at the logs for the docker containers I get this:

requests.exceptions.ConnectionError: HTTPConnectionPool(host='host.docker.internal', port=4200): Max retries exceeded with url: /graphql/alpha (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f7739090a90>: Failed to establish a new connection: [Errno -2] Name or service not known'))

. I'm guessing it means the container can't find the graphql api? I'm running under Ubuntu. I'm ssh tunnelling into a jupyter notebook on an Azure VM and running from there - could that be making a difference? thanks!!

Hey guys. Big fan of the product, it’s really cut down on our manual ETL work load. 1 issue: setting the time out in a

ShellTask

doesn’t seem to work for me. I have an S3 sync that occasionally hang (working to figure that out), and as a temporary solution I was hoping to use a timeout + retry. This has solved the issue in the past. I’ve set the timeout to 600 (600 seconds, 10 minutes), and yet I’m getting a task that runs for 6 hours+ when the shell task hangs. On Cloud (Scheduler tier), I can see that my retry and retry delay parameters are set, but I’m not sure if there’s a way to check whether a timeout has been configured on a task. It’s a fairly simple task (top level, only 1 dependency, unmapped), and everything works just fine if I manually restart the task on the Cloud UI (I even see the retry count increment). I’m wondering if there are any additional inputs I needed to configure other than timeout + retry in order to get the timeout to work, or if this is an issue other people have seen before?. Thanks!

Hey there, first time here. Firstly, fantastic product you have built, seems to have massive potential, coming from someone who used to work with Airflow. The documentation has been super helpful and I would like to see more video demos in the future. My question is, what would you recommend would be the best way to run Agents in a production environment, say EC2, when using Prefect's Cloud feature? I mean: • should the Agent run continuously in the background of an EC2 instance? • should the Agent be embedded in the Python Flow script and run as a container • should we have several Agents running and associated to flows based on

labels

Basically, some best practices around Agents in a production setting. Thanks

Hello friends, I started looking into generating some performance benchmarks with prefect+dask, and I was wondering if anyone here has done that before and could provide some pointers. Right now, I only have my laptop but am willing to figure out how to set up a proper dask cluster to do this.

Hi, I am just installing Prefect on my Windows 10 PC and have received the following error. I have tried many things to solve my issue and no luck so far. Would like to get some help on this.... I was running the install

pip install prefect

Building wheels for collected packages: pendulum
  Building wheel for pendulum (PEP 517) ... error
  ERROR: Command errored out with exit status 1:
   command: 'c:\users\zhang\appdata\local\programs\python\python38\python.exe' 'c:\users\zhang\appdata\local\programs\python\python38\lib\site-packages\pip\_vendor\pep517\_in_process.py' build_wheel 'C:\Users\zhang\AppData\Local\Temp\tmpjjs207ax'
       cwd: C:\Users\zhang\AppData\Local\Temp\pip-install-2pd94jc4\pendulum
  Complete output (24 lines):
  Traceback (most recent call last):
    File "setup.py", line 2, in <module>
      from setuptools import setup
  ModuleNotFoundError: No module named 'setuptools'
  Traceback (most recent call last):
    File "c:\users\zhang\appdata\local\programs\python\python38\lib\site-packages\pip\_vendor\pep517\_in_process.py", line 257, in <module>
      main()
    File "c:\users\zhang\appdata\local\programs\python\python38\lib\site-packages\pip\_vendor\pep517\_in_process.py", line 240, in main
      json_out['return_val'] = hook(**hook_input['kwargs'])
    File "c:\users\zhang\appdata\local\programs\python\python38\lib\site-packages\pip\_vendor\pep517\_in_process.py", line 181, in build_wheel
      return _build_backend().build_wheel(wheel_directory, config_settings,
    File "C:\Users\zhang\AppData\Local\Temp\pip-build-env-e3fac8fx\overlay\Lib\site-packages\poetry\core\masonry\api.py", line 57, in build_wheel
      return unicode(WheelBuilder.make_in(poetry, Path(wheel_directory)))
    File "C:\Users\zhang\AppData\Local\Temp\pip-build-env-e3fac8fx\overlay\Lib\site-packages\poetry\core\masonry\builders\wheel.py", line 56, in make_in
      wb.build()
    File "C:\Users\zhang\AppData\Local\Temp\pip-build-env-e3fac8fx\overlay\Lib\site-packages\poetry\core\masonry\builders\wheel.py", line 82, in build
      self._build(zip_file)
    File "C:\Users\zhang\AppData\Local\Temp\pip-build-env-e3fac8fx\overlay\Lib\site-packages\poetry\core\masonry\builders\wheel.py", line 102, in _build
      self._run_build_command(setup)
    File "C:\Users\zhang\AppData\Local\Temp\pip-build-env-e3fac8fx\overlay\Lib\site-packages\poetry\core\masonry\builders\wheel.py", line 130, in _run_build_command
      subprocess.check_call(
    File "c:\users\zhang\appdata\local\programs\python\python38\lib\subprocess.py", line 364, in check_call
      raise CalledProcessError(retcode, cmd)
  subprocess.CalledProcessError: Command '['c:\\users\\zhang\\appdata\\local\\programs\\python\\python38\\python.exe', 'setup.py', 'build', '-b', 'build']' returned non-zero exit status 1.
  ----------------------------------------
  ERROR: Failed building wheel for pendulum
Failed to build pendulum
ERROR: Could not build wheels for pendulum which use PEP 517 and cannot be installed directly

Hi! Does anyone have any tips on running Docker tasks in a Flow running on a Docker agent? Mounting the hosts’ Docker socket does not seem to be a good practice…

looking to use prefect with dask-ml on the default DaskExecutor.. how might I get the sklearn bits to use dask as the joblib backend as referenced here: https://ml.dask.org/joblib.html ?