@Marvin how can I trigger a deployment run from a PostgreSQL database?

To trigger a deployment run from a PostgreSQL database using Prefect 3.x, you can utilize deployment triggers. Prefect provides a mechanism to configure event-driven deployments through deployment triggers, which can be linked to specific deployments to run them based on certain events. Here's a concise way to set this up: 1. Define Triggers in `prefect.yaml`: You can specify triggers for your deployment in a

prefect.yaml

file. These triggers can be based on custom events that you might define, such as a database update or insert. 2. Use Python for Triggers: If you prefer using Python, you can import trigger types like

DeploymentEventTrigger

from

prefect.events

. This allows you to create more complex and customized triggers programmatically. 3. Database Integration: To integrate with PostgreSQL, you might need a separate mechanism to listen for changes in your database, such as using a database trigger or a change data capture tool. This mechanism should then emit an event that Prefect can recognize to trigger the deployment. For more detailed information, you can refer to the Prefect documentation on automations and triggers. If you need further guidance on setting up the database event listener, feel free to ask!

@Marvin can you write the

prefect.yaml

associated?

To create a

prefect.yaml

file with deployment triggers, you'll need to define the triggers that will respond to events. Here's a basic example of how you might set it up:

yaml
version: 1

deployments:
  - name: my_deployment
    flow: my_flow.py
    parameters:
      param1: value1
    triggers:
      - type: DeploymentEventTrigger
        event: database.record_inserted
        resource: my_database_resource

### Explanation: - version: Specifies the version of the configuration. - deployments: A list of deployments you want to configure. - name: The name of the deployment. - flow: The path to your flow script. - parameters: Any parameters you need to pass to the flow. - triggers: A list of triggers for the deployment. - type: The type of trigger, such as

DeploymentEventTrigger

. - event: The event that triggers the deployment. In this example, it's a custom event like

database.record_inserted

. - resource: The resource associated with the event. You might define this based on your database setup. This is a basic example, and you'll need to adapt it to fit your specific use case, particularly how you define and emit events from your PostgreSQL database.

@Marvin how can I create the custom event

database.record_inserted

?

To create a custom event like

database.record_inserted

in Prefect, you can use the

emit_event

function provided by the Prefect Python SDK. Here's how you can set it up: ### Step-by-Step Guide: 1. Emit Custom Events from Python Code: You can call the

emit_event

function within your Python code to send a custom event to the Prefect API. This can be done inside or outside of a task or flow. 2. Function Usage: The

emit_event

function requires two main arguments: - `event`: The name of the event you want to emit, e.g.,

database.record_inserted

. - `resource`: A dictionary specifying the resource ID, e.g.,

{"prefect.resource.id": "my_database_resource"}

. 3. Optional Payload: If you need to include additional data in the event, you can specify a dictionary of values for the

payload

parameter. ### Example Code:

python
from prefect import task
from prefect.events import emit_event

@task
def insert_record_to_database():
    # Code to insert record into PostgreSQL
    # ...

    # Emit a custom event
    emit_event(
        event="database.record_inserted",
        resource={"prefect.resource.id": "my_database_resource"},
        payload={"record_id": "12345", "status": "inserted"}
    )

# This task can be part of a larger flow

### Additional Resources: - You can read more about emitting custom events in the Prefect documentation on events. This setup will allow you to trigger Prefect deployments based on database insertions by emitting events when such actions occur.

@Marvin The INSERT in database is made from another system than my Prefect Python code. How can I track this insert and create the custom event?

To track an INSERT operation in a PostgreSQL database made by an external system and trigger a custom event in Prefect, you can follow these steps: 1. Database Trigger: - Set up a PostgreSQL trigger on the table where the INSERT operation occurs. This trigger can call a function whenever a new row is inserted. 2. Notify External System: - Use the PostgreSQL

NOTIFY

command within the trigger function to send a notification to an external listener. 3. Listener Script: - Write a Python script that listens for these notifications. This script can use the

psycopg2

library to connect to the database and listen for notifications. - When a notification is received, the script can then use the

emit_event

function from Prefect to create a custom event. ### Example Setup: PostgreSQL Trigger and Function:

sql
CREATE OR REPLACE FUNCTION notify_insert()
RETURNS TRIGGER AS $$
BEGIN
  PERFORM pg_notify('record_inserted', NEW.id::text);
  RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER record_insert_trigger
AFTER INSERT ON your_table
FOR EACH ROW EXECUTE FUNCTION notify_insert();

Python Listener Script:

python
import psycopg2
import select
from prefect.events import emit_event

def listen_for_inserts():
    conn = psycopg2.connect("dbname=your_db user=your_user password=your_password")
    conn.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT)
    cur = conn.cursor()
    cur.execute("LISTEN record_inserted;")

    print("Waiting for notifications on channel 'record_inserted'")
    while True:
        if select.select([conn], [], [], 5) == ([], [], []):
            continue
        else:
            conn.poll()
            while conn.notifies:
                notify = conn.notifies.pop(0)
                print("Got NOTIFY:", notify.pid, notify.channel, notify.payload)

                # Emit a custom event to Prefect
                emit_event(
                    event="database.record_inserted",
                    resource={"prefect.resource.id": "my_database_resource"},
                    payload={"record_id": notify.payload}
                )

if __name__ == "__main__":
    listen_for_inserts()

### Explanation: - Database Trigger and Function: This setup listens for any new row inserted into

your_table

and sends a notification with the inserted row's ID. - Python Listener Script: This script listens for notifications on the

record_inserted

channel and emits a custom event to Prefect when a notification is received. This approach allows you to integrate external database actions with Prefect's event system efficiently.