@Marvin my workflow need to use a private key (written in an

.env

file) to be able to download data from external source. My deployment returns

httpcore.ConnectError: All connection attempts failed

What should I do now?

Your issue with

httpcore.ConnectError: All connection attempts failed

could be related to several factors, including misconfigured environment variables, network issues, or incorrect usage of private keys within your Prefect deployment. Here are some steps and resources to help you troubleshoot and resolve the problem: 1. Environment Variables: Ensure that your environment variables, including any private keys required for accessing external data sources, are correctly set in your deployment environment. You can use Prefect's templating syntax in your

prefect.yaml

file to include these variables. See more about using environment variables in Prefect deployments. 2. Network Configuration: If your deployment needs to communicate through a proxy or has specific network requirements, ensure that the necessary proxy settings are configured. Prefect's documentation provides guidance on using proxies with Prefect Cloud. 3. API Configuration: Verify that your Prefect API configuration is correct. If you're using Prefect Cloud, ensure that you are authenticated and that the API URL is correctly set. You can follow the steps to connect to Prefect Cloud. 4. Debugging: Check the logs for more details on the error, as it might provide additional context on why the connection attempts are failing. There are known issues related to connection errors not being logged explicitly, as seen in this GitHub issue. If the error persists after these checks, consider exploring Prefect's community forums or GitHub issues for similar problems and potential fixes.

@Marvin Why the prefect server is running on port

4200

but the flow (started by docker compose) is started on other temp-server

8237

The behavior you're observing, where the Prefect server runs on port

4200

but the flow is executed on a different temporary server port (e.g.,

8237

), is typical in Prefect when using Docker Compose. Here's why this happens: 1. Server Port Configuration: The Prefect server is configured to run on a specific port, such as

4200

, as defined in your

docker-compose.yml

file. This port is used for the Prefect UI and API interactions. The server listens on this port to manage flow runs, task states, and other metadata. 2. Flow Execution Port: When a flow is started, it might run on a different port because Prefect dynamically allocates ports for executing flows. This is often handled by the Prefect worker or agent, which may use available ports to run tasks and communicate with the server. The dynamic port allocation helps manage multiple concurrent flows and tasks without port conflicts. 3. Docker Compose Setup: Your

docker-compose.yml

likely specifies the server and worker services with their respective configurations. The server is explicitly set to port

4200

, while the worker or flow execution does not have a fixed port, allowing it to use any free port available. 4. Issue Context: There are known issues and discussions about how Prefect manages ports and flow executions, such as the behavior of flows hanging if a worker crashes. You can find more context in this GitHub issue. For more detailed configuration, ensure your

docker-compose.yml

is set up correctly, with the server's port exposed and the worker connected to the server's API. You can refer to Prefect's server documentation for additional guidance.

@Marvin I have this error when deploying my flow inside

docker-compose

. What is it wrong?

server-1   | Server stopped!
server-1   | Traceback (most recent call last):
server-1   |   File "/usr/local/lib/python3.9/site-packages/prefect/cli/_utilities.py", line 44, in wrapper
server-1   |     return fn(*args, **kwargs)
server-1   |   File "/usr/local/lib/python3.9/site-packages/prefect/cli/server.py", line 299, in start
server-1   |     _run_in_foreground(server_settings, host, port, keep_alive_timeout, no_services)
server-1   |   File "/usr/local/lib/python3.9/site-packages/prefect/cli/server.py", line 361, in _run_in_foreground
server-1   |     app=create_app(final=True, webserver_only=no_services),
server-1   |   File "/usr/local/lib/python3.9/site-packages/prefect/server/api/server.py", line 649, in create_app
server-1   |     ui_app = create_ui_app(ephemeral)
server-1   |   File "/usr/local/lib/python3.9/site-packages/prefect/server/api/server.py", line 451, in create_ui_app
server-1   |     create_ui_static_subpath()
server-1   |   File "/usr/local/lib/python3.9/site-packages/prefect/server/api/server.py", line 426, in create_ui_static_subpath
server-1   |     os.makedirs(static_dir)
server-1   |   File "/usr/local/lib/python3.9/os.py", line 225, in makedirs
server-1   |     mkdir(name, mode)
server-1   | PermissionError: [Errno 13] Permission denied: '/usr/local/lib/python3.9/site-packages/prefect/server/ui_build'
server-1   | An exception occurred.

The error you're encountering,

PermissionError: [Errno 13] Permission denied

, is typically related to file or directory permissions. In your case, it seems to be occurring when the Prefect server is trying to create a directory at

/usr/local/lib/python3.9/site-packages/prefect/server/ui_build

. Here are some steps to resolve this issue: 1. Directory Permissions: Ensure that the user running the Docker container has the necessary permissions to create directories and write to the specified path. You might need to adjust the permissions of the parent directory or run the container with a user that has the appropriate permissions. 2. Docker Volume: If you're using Docker volumes, ensure they are correctly mounted and accessible. You can specify the volume in your

docker-compose.yml

to ensure the server can write to the necessary directories. 3. Environment Variables: Check if there are any environment variables that can redirect or configure the UI build path to a location with appropriate permissions. 4. Custom Dockerfile: If necessary, you can create a custom Dockerfile to adjust permissions or set up the environment as needed before starting the server. 5. Workaround: As suggested in similar issues, you might temporarily set an alternative directory path using environment variables or Docker configurations to bypass the permission issue. If the issue persists, you might want to explore Prefect's community forums or GitHub issues for similar problems and potential solutions.

@Marvin what does this error mean

asyncio.exceptions.CancelledError: Cancelled by cancel scope 7faaba86ec10

The error

asyncio.exceptions.CancelledError: Cancelled by cancel scope

indicates that an asyncio task was cancelled. In the context of Prefect, this usually happens when a flow run or task is intentionally cancelled, either through the Prefect UI, CLI, or programmatically. Here are some key points about cancellation in Prefect: 1. Scope of Cancellation: Prefect uses a concept of "cancel scope" to ensure that the correct infrastructure or task is cancelled. This involves unique identifiers for processes, Docker containers, or Kubernetes jobs to avoid cancelling the wrong task. 2. Cancellation Process: If a flow run or task is cancelled, Prefect attempts to stop the associated infrastructure. If the infrastructure does not support cancellation or cannot be found, the flow run is marked as cancelled, but the cancellation might not be enforced. 3. CLI and UI: You can cancel a flow run using the Prefect CLI with the command

prefect flow-run cancel

and the flow run ID. Alternatively, you can cancel it through the Prefect UI. 4. Issues with Cancellation: Some common issues include mismatched identifier scopes, missing infrastructure, or unexpected errors during cancellation. In such cases, another worker might attempt the cancellation. For more details, you can refer to the Prefect cancellation documentation.

@Marvin what about this

readwrite  |   File "/usr/local/lib/python3.11/site-packages/httpx/_transports/default.py", line 118, in map_httpcore_exceptions
readwrite  |     raise mapped_exc(message) from exc
readwrite  | httpx.ConnectError: All connection attempts failed

The error

httpx.ConnectError: All connection attempts failed

typically indicates that the HTTPX library, which Prefect uses for making HTTP requests, cannot establish a connection to the specified server or endpoint. Here are some potential reasons and solutions: 1. Network Configuration: Ensure that your network allows outbound connections to the required URLs. If you're using Prefect Cloud, you should whitelist URLs such as

app.prefect.cloud

,

api.prefect.cloud

, and other related endpoints. 2. Proxy Settings: If your environment requires a proxy for outbound connections, ensure that the

HTTPS_PROXY

and

SSL_CERT_FILE

environment variables are set correctly. HTTPX respects these proxy settings, which can be crucial in environments with strict network policies. 3. API Configuration: Verify that the

PREFECT_API_URL

is correctly configured. This should be set to the appropriate endpoint, such as

<https://api.prefect.cloud>

for Prefect Cloud users. 4. Environment Variables: Use the

prefect config view

CLI command to check that your environment variables are correctly set for accessing Prefect Cloud or your Prefect server. For more detailed troubleshooting steps, you can refer to the Prefect Cloud troubleshooting guide.

@Marvin which environment setting must be done to run

docker compose

using

prefect

flows?

To run Prefect flows using Docker Compose, you'll need to configure several environment settings and ensure your

docker-compose.yml

file is correctly set up. Here's a concise guide: 1. Environment Variables: - PREFECT_API_URL: Set this to the URL of your Prefect server or Prefect Cloud API. For local development, it might be

<http://localhost:4200/api>

. - PREFECT_API_KEY: If you're using Prefect Cloud, set this to your Prefect Cloud API key for authentication. 2. Docker Compose Configuration: - Ensure your

docker-compose.yml

file defines the Prefect service correctly. Here's a basic example:

yaml
     services:
       prefect:
         image: prefecthq/prefect:3.0.0rc2-python3.12
         environment:
           PREFECT_HOME: /data
         command: prefect server start --host 0.0.0.0
         ports:
           - "4200:4200"
         volumes:
           - prefect-data:/data
           - .:/app

     volumes:
       prefect-data: {}

3. .env File: - Create a

.env

file to store your environment variables. This file should be in the same directory as your

docker-compose.yml

.

bash
     PREFECT_API_URL=<http://localhost:4200/api>
     PREFECT_API_KEY=pnu_1234567890abcdefghijklmnopqrstuvwxyz

4. Commands: - Start the services with

docker compose up -d

. - Stream logs using

docker compose logs -f

. - Stop the services with

docker compose down

. These configurations ensure that your Prefect server and flows are correctly set up and accessible via Docker Compose. For more detailed guidance, you can refer to Prefect's documentation.