@Marvin I am configuring prefect-server helm to use external postgres. The server stops and the logs contain the error: OSError: Multiple exceptions: [Errno 111] Connect call failed ('::1', 5432, 0, 0), [Errno 111] Connect call failed ('127.0.0.1', 5432)

It appears you are having trouble connecting to an external PostgreSQL database when setting up Prefect Server with Helm. The

OSError

suggests a connectivity problem. Here are a few steps based on the Prefect documentation to check: 1. Database Connection URL: Confirm that your

DATABASE_CONNECTION_URL

environment variable is set correctly with your external database credentials and hostname. See Here

DATABASE_CONNECTION_URL="<postgresql+asyncpg://username:password@hostname:port/database>"

Replace

username

,

password

,

hostname

,

port

, and

database

with your actual details. 2. Hostname and Port: Ensure the hostname of the PostgreSQL is correctly specified and that the port is accessible. If the database is not hosted on

localhost

, you should provide the appropriate hostname/IP address instead. 3. Firewall and Network: Check if there are any firewalls or network configurations that might be preventing the connection to the database. 4. Docker Quick Start: If you are using Docker, here is a quick start command to configure a PostgreSQL database with Docker:

docker run -d --name prefect-postgres -v prefectdb:/var/lib/postgresql/data -p 5432:5432 -e POSTGRES_USER=postgres -e POSTGRES_PASSWORD=yourTopSecretPassword -e POSTGRES_DB=prefect postgres:latest

See Here If you've gone through these steps and are still encountering issues, it may be useful to check any network issues between your Helm-deployed services and the external PostgreSQL instance. Additionally, confirming that the external PostgreSQL service is running and properly configured would be important steps. Remember also to check the logs for any additional error messages that could provide more context.

@Marvin I am using kubernetes. PREFECT_API_DATABASE_CONNECTION_URL: <set to the key 'connection-string' in secret 'prefect-postgres-secret'> Optional: false

You are trying to configure the Prefect Server to use an external PostgreSQL database on Kubernetes by setting the

PREFECT_API_DATABASE_CONNECTION_URL

. In Kubernetes, this is typically done by using Kubernetes secrets to securely pass credentials. The Prefect documentation provides some information regarding deployment to Kubernetes, but specific guidelines for setting up an external Postgres database with Kubernetes secrets may be less detailed. However, you can follow the principles used for configuring other types of secrets in Kubernetes for your database connection. See here for Kubernetes deployment guide Here is a step-by-step guide to help with the configuration, based on Kubernetes practices: 1. Create a Kubernetes Secret with your PostgreSQL connection information. This can be done with the following command:

sh
    kubectl create secret generic prefect-postgres-secret \
      --from-literal=connection-string="<postgresql+asyncpg://username:password@hostname:port/database>"

Replace

username

,

password

,

hostname

,

port

, and

database

with your actual PostgreSQL credentials. 2. Configure your Helm values.yaml file to use the secret for the

PREFECT_API_DATABASE_CONNECTION_URL

. You might configure it like this:

yaml
    env:
      PREFECT_API_DATABASE_CONNECTION_URL:
        valueFrom:
          secretKeyRef:
            name: prefect-postgres-secret
            key: connection-string

3. Deploy/Upgrade your Prefect Server with the updated Helm chart values.yaml that includes the above environment variable settings. Remember to double-check your secret names, key names, and ensure that your PostgreSQL instance accepts connections from your Kubernetes cluster. If you've set everything correctly, the Kubernetes pods should pick up the database connection URL from the secrets you've set and successfully connect to your external PostgreSQL instance.

@Marvin Does this error indicate that prefect is looking for the database on the local ip? OSError: Multiple exceptions: [Errno 111] Connect call failed ('::1', 5432, 0, 0), [Errno 111] Connect call failed ('127.0.0.1', 5432)

The error message you're seeing:

OSError: Multiple exceptions: [Errno 111] Connect call failed ('::1', 5432, 0, 0), [Errno 111] Connect call failed ('127.0.0.1', 5432)

indicates that Prefect tried to connect to a database using the IPv6 localhost address

::1

and the IPv4 localhost address

127.0.0.1

, both on port

5432

, which is the default port for PostgreSQL. This error suggests that Prefect is attempting to establish a connection to a PostgreSQL instance running on the local host machine inside your Kubernetes pod rather than to an external instance. This could happen if the configuration (such as environment variables or Helm values) is incorrect or not being picked up properly, and therefore Prefect falls back to the default localhost address. You need to ensure that your configuration is pointed at the correct external database IP address or DNS name instead of localhost. This usually involves setting the correct environment variable for the connection string using Kubernetes secrets, as I described in the previous message. Make sure that Kubernetes has properly injected the environment variable from the secret into the pods where Prefect is running.

@Marvin USing kubectl describe pod. The environment variable for PREFECT_API_DATABASE_CONNECTION_URL is pointing at the secret created? Why would it default to local host? Environment: HOME: /home/prefect PREFECT_API_URL: http://localhost:4200/api PREFECT_DEBUG_MODE: false PREFECT_LOGGING_SERVER_LEVEL: WARNING PREFECT_SERVER_API_HOST: 0.0.0.0 PREFECT_SERVER_API_PORT: 4200 PREFECT_UI_ENABLED: true PREFECT_UI_STATIC_DIRECTORY: /ui_build PREFECT_API_DATABASE_CONNECTION_URL: <set to the key 'connection-string' in secret 'prefect-postgres-secret'> Optional: false

The text

<set to the key 'connection-string' in secret 'prefect-postgres-secret'>

in the output of

kubectl describe pod

is not the actual environment variable value; it's a placeholder indicating that the

PREFECT_API_DATABASE_CONNECTION_URL

should be set from a key within the Kubernetes secret

prefect-postgres-secret

. This placeholder indicates that you're likely looking at a template or a descriptor rather than the resolved configuration. Based on this, there are a few possibilities as to why Prefect is defaulting to localhost for the database: 1. The secret is not properly configured: The secret

prefect-postgres-secret

must exist in the same namespace where your Prefect components are running and must contain the correct connection-string data. 2. The secret key reference is incorrect: Ensure that the environment variable in your deployment configuration correctly references the existing key in the secret. 3. The environment variable is not being substituted properly: This could be due to a mistake in the Helm chart values or a misconfiguration in the Kubernetes deployment manifest. 4. Prefect components are not picking up the environment variable: This could happen if the pods were not properly restarted after the secret or configuration update. You should verify the following: - Ensure the secret exists and has the correct

connection-string

key with the right database URL:

sh
    kubectl get secret prefect-postgres-secret -o yaml

- Double-check the syntax in your Helm chart or Kubernetes deployment manifest to ensure that the environment variable is properly set to use the secret's value. - If necessary, restart the Prefect components so they pick up the latest configuration. - If everything seems to be correct, but you're still seeing issues, it might be worth checking if the configuration is being overridden somewhere else, such as in a config file within the container or by an entrypoint script.

@Marvin What should the connection string look like? should the connection string include the port?

Yes, the connection string should include the port number along with other details required to connect to the PostgreSQL database. A typical PostgreSQL connection string in Prefect would look something like this:

<postgresql+asyncpg://username:password@host:port/database_name>

Let's break down the components: - postgresql+asyncpg: This indicates the database driver;

postgresql

is the database, and

asyncpg

is the async driver for PostgreSQL used by Prefect. - username: The username for your PostgreSQL database. - password: The password for the PostgreSQL user. - host: The hostname or IP address where your PostgreSQL server is running. If it's an external database, this should be the publicly accessible endpoint or IP address. - port: The port number on which your PostgreSQL server is listening. The default port for PostgreSQL is

5432

. - database_name: The name of the actual database you are connecting to. For instance, if you have a PostgreSQL user

admin

, with password

secret

, running on a host with IP address

10.0.0.1

, listening to the default port

5432

, and the database name is

prefect_db

, your connection string would look like this:

<postgresql+asyncpg://admin:secret@10.0.0.1:5432/prefect_db>

This string should be stored as the value in your Kubernetes secret under a key named something like

connection-string

, which your Kubernetes deployment manifest or Helm values file would then reference. Remember to keep your actual connection string secure and not expose sensitive credentials.

@Marvin I had a '\' after the '@' in the connection string...

Ah, that's likely the source of your troubles. The backslash

\

is used as an escape character in many contexts, including strings in configuration files. Having an unintended backslash in your connection string could cause the database connection parameters to be parsed incorrectly, leading to connection errors like the one you are experiencing. Your connection string should not have a backslash before the

@

symbol. It should follow the standard URI format for PostgreSQL connections as previously described:

<postgresql+asyncpg://username:password@hostname:port/database_name>

With no extra backslashes. Make sure to update your Kubernetes secret or configuration to remove the extraneous backslash and any other typos or syntax errors, and then ensure that your Prefect Server components have been restarted to pick up the new, corrected configuration. After making the correction, verify that the

PREFECT_API_DATABASE_CONNECTION_URL

environment variable in your Prefect Server pods reflects the correct connection string without any unintended characters. If the connection string is now set correctly, Prefect should attempt to connect to the specified external PostgreSQL database instead of defaulting to localhost.