Hey everyone, so I'm using the dask taskrunner to ...
# ask-community
d
Hey everyone, so I'm using the dask taskrunner to run a temporary cluster on AWS ECS (dask_cloudprovider.aws), I just wanted to ask if anyone knows if the scheduler/everything in dask automatically resorts to using a local cluster if it fails to connect to ECS? I've noticed that the logs show the dask scheduler and workers running on an ip address such as 127.0.0.1 which is the localhost. Yet I don't seem to notice any warning message indicating that it can't connect to AWS
n
the scheduler/everything in dask automatically resorts to using a local cluster if it fails to connect to ECS
I seem to remember that you might have posted this somewhere else. Can you show/link the code that you're using to configure your task runner?
d
I can't share/link the exact code I'm using due to privacy issues (project for a company), but here's the basic gist of what I have... from prefect_dask import DaskTaskRunner from dask_cloudprovider.aws import FargateCluster
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def fargate_cluster(
    n_workers=4,
    scheduler_task_definition_arn: str = {task_definition},
    execution_role_arn: str = {execution_role},
    scheduler_timeout: str = "15 minutes",
    security_groups: list[str] = {security_groups]
):
    return FargateCluster(
        n_workers=n_workers,
        scheduler_task_definition_arn=scheduler_task_definition_arn,
        execution_role_arn=execution_role_arn,
        scheduler_timeout=scheduler_timeout,
        security_groups=security_groups,
    )

@flow(task_runner=DaskTaskRunner(
        cluster_class=fargate_cluster
))
def test_cluster():
  flow...
In terms of providing credentials, I used environment variables (ie. setting $AWS_PROFILE)
n
that doesn't look quite right, it seems you're giving an instance to
cluster_class
instead of a class
the kwargs should go in
cluster_kwargs
I would think
@Marvin can you dig up details on the signature and available kwargs for DaskTaskRunner?
m
thought for 60.1 seconds
n
or am i misunderstanding, you're treating the callable as the "class"
m
In Prefect 3.x, the DaskTaskRunner has been moved to a separate package called
prefect-dask
. Here's what you need to know: 1. First, install the package:
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bash
pip install prefect-dask
2. Then import and use it as:
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python
from prefect_dask import DaskTaskRunner
The DaskTaskRunner accepts several key configuration options: - `cluster_kwargs`: Dictionary of kwargs to pass to the Dask cluster - `adapt_kwargs`: Dictionary of kwargs for cluster adaptation (auto-scaling) - `client_kwargs`: Dictionary of kwargs to pass to the Dask client - `cluster_class`: The class of Dask cluster to use (defaults to LocalCluster if not specified) A typical configuration might look like:
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python
from prefect_dask import DaskTaskRunner

runner = DaskTaskRunner(
    cluster_kwargs={"n_workers": 2},
    adapt_kwargs={"minimum": 1, "maximum": 4}
)

@flow(task_runner=runner)
def my_flow():
    # your flow code here
    pass
Given your interest in container-based deployments, you might want to consider using Dask's
ECSCluster
for AWS ECS integration. This would allow you to dynamically spin up Dask workers in your ECS environment. For more details and the latest documentation, visit: https://prefecthq.github.io/prefect-dask/ Would you like me to dig deeper into any specific aspect of the DaskTaskRunner configuration, particularly around ECS integration?
d
I've also tried the following in the past (per the docs)...
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@flow(task_runner=DaskTaskRunner(
        cluster_class="dask_cloudprovider.aws.FargateCluster",
        cluster_kwargs={kwargs}
))
But I saw the same result, hence why I tried being more specific and passing in the cluster/callable as the class.
I got the idea of passing in the callable as the
cluster_class
from this github issue on the repository, specifically Anna Geller's implementation
Is there a preferred way to provide AWS credentials when calling the dask runner? Like I mentioned before I've been using the $AWS_PROFILE environment variable
@Marvin Yes, please help in integrating ECS with the DaskTaskRunner. Moreover, what would be a good way for me to provide AWS credentials in case that is the issue? Right now I'm using the environment variable $AWS_PROFILE
m
thought for 55.7 seconds
Based on the research, I can provide you with a comprehensive guide for setting up DaskTaskRunner with ECS. Here's how to do it: 1. First, install the required packages:
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bash
pip install prefect-dask "dask-cloudprovider[aws]" dask
2. Here's how to configure the DaskTaskRunner with ECS:
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python
from prefect_dask import DaskTaskRunner
from dask_cloudprovider.aws import FargateCluster

runner = DaskTaskRunner(
    cluster_class=FargateCluster,
    cluster_kwargs={
        "image": "daskdev/dask:latest",  # You can customize this
        "n_workers": 2,
        "fargate_use_private_ip": False,  # Set to True if using private subnets
        "aws_region": "your-region",      # e.g., "us-east-1"
        "environment": {
            "AWS_PROFILE": "${AWS_PROFILE}",  # This will use your environment variable
        }
    },
    adapt_kwargs={
        "minimum": 1,
        "maximum": 10
    }
)

@flow(task_runner=runner)
def your_flow():
    # your flow code here
    pass
3. For AWS credentials, since you're using AWS_PROFILE, there are several approaches you can take: a. Environment Variables (Your current approach):
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python
   # The environment section in cluster_kwargs above will handle this
   # Make sure AWS_PROFILE is set in your environment
b. Alternatively, you can use explicit credentials:
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python
   cluster_kwargs={
       # ... other kwargs ...
       "environment": {
           "AWS_ACCESS_KEY_ID": "your-access-key",
           "AWS_SECRET_ACCESS_KEY": "your-secret-key",
           "AWS_SESSION_TOKEN": "your-session-token",  # if using temporary credentials
       }
   }
4. Important considerations: - Ensure your IAM role/user has the necessary permissions for ECS operations. The minimum required permissions include: -
ecs:CreateCluster
-
ecs:RegisterTaskDefinition
-
ecs:RunTask
-
ecs:DescribeTasks
-
ecs:ListTasks
-
iam:GetRole
-
iam:PassRole
-
ec2:DescribeSubnets
-
ec2:DescribeVpcs
-
ec2:DescribeSecurityGroups
- If you're running in a VPC, make sure to configure: - Proper subnet access - Security group rules - NAT Gateway or VPC Endpoints for private subnets 5. Container Image Considerations: - The default
daskdev/dask:latest
image should work for basic operations - For custom dependencies, you might need to build your own image based on the Dask image - Ensure your image has all the required Python packages installed If you run into any issues with task deserialization (which can happen), you might need to ensure that: 1. All dependencies are consistently installed across your local environment and the Dask workers 2. The Python versions match between your local environment and the workers 3. Any custom objects you're passing to tasks are properly serializable Would you like me to elaborate on any of these aspects, particularly around the container image configuration or IAM roles setup?
n
hmm i don't have a ton of experience with the 3rd party dask cluster implementations unfortunately but what I suspect is happening here is that the "returning a callable as the class" is probably fine but reaching that cluster is still failing for some reason (credentials, permissions or the like) and then its falling back to the local cluster as you mention maybe we can add some more helpful logging in that case, will take a look at that
d
I see, I'll go through my IAM permissions/credentials and whatnot to try and see if that changes anything. Thanks anyways! Do you know anyone else on the Prefect team that might have more experience with dask or the task runners implementation in general? Or is this something I should put up on the github repo?
n
yea a discussion would be good here i think. we implemented the cluster class / kwargs (passthrough) approach to allow all cluster options supported by the upstream, so users probably have more context than the team on how to use a given third party in this case
d
Understood. I did notice that in another script I'm able to successfully connect to AWS ECS using the
dask_cloudprovider.aws
library directly. Am I correct in understanding that by "allow[ing] all cluster options supported by the upstream", this means that whatever parameters that are accepted/needed by the
dask_cloudprovider.aws
function that I'm using (FargateCluster in this case) can be passed in the
cluster_kwargs
field in the Prefect dask task runner?
n
yes
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