The Prefect documentation about deplyments are super vague. This post explains how to add deployments.

Table of content

• Where are deployment codes located in the docs
• What is a deployment
• Define and run prefect deployments
• A minimal example
• The prefect server

Where are deployment codes located in the docs

Deployments are not located inside the Deployment section, but rather in the flows section.

What is a Deployment

Typically, deployments, whererver you define them, populate a class like this which you don’t need to write:

class Deployment:
    """
    Structure of the schema defining a deployment
    """

    # required defining data
    name: str 
    flow_id: UUID
    entrypoint: str
    path: str = None

    # workflow scheduling and parametrization
    parameters: Optional[Dict[str, Any]] = None
    parameter_openapi_schema: Optional[Dict[str, Any]] = None
    schedules: list[Schedule] = None
    paused: bool = False
    trigger: Trigger = None

    # metadata for bookkeeping
    version: str = None
    description: str = None
    tags: list = None

    # worker-specific fields
    work_pool_name: str = None
    work_queue_name: str = None
    infra_overrides: Optional[Dict[str, Any]] = None
    pull_steps: Optional[Dict[str, Any]] = None

Deployments are essentially defining metadata

Define and run prefect deployments

Deployments can be created like this. where hello_world is a flow

hello_world.serve(name="my-first-deployment",
                      tags=["onboarding"],
                      parameters={"goodbye": True},# flow params
                      interval=60)

You can run the deployment like this

from prefect.deployments import run_deployment
run_deployment(name="hello_world/my-first-deployment")

Or, you can run on the commandline

prefect deployment run 'hello_world/my-first-deployment'

A minimal example

from prefect import flow
from prefect import task

@task
def laugh():
    pass

@task
def run():
    pass

@task
def swim():
    pass

@task
def walk():
    pass

@flow
def first_subflow():
    laugh()
    run()

@flow
def second_subflow():
    laugh()
    run()

@flow
def pipeline():
    # do stuffs
    first_subflow()
    second_subflow()




if __name__ == "__main__":
    pipeline.serve(name="ml-pipeline")

Then on the shell we run

prefect deployment run 'pipeline/ml-pipeline'

It will produce something like this

Creating flow run for deployment 'pipeline/canon-pipeline'...
Created flow run 'beautiful-nyala'.
└── UUID: 45ef0da2-ff32-472e-a9b8-8fecdeb95b10
└── Parameters: {}
└── Job Variables: {}
└── Scheduled start time: 2024-07-03 19:20:02 +04 (now)
└── URL: http://path-to-server:4200/flow-runs/flow-run/45ef0da2-ff32-472e-a9b8-8fecdeb95b10

The prefect server

If you go to the prefect server you can see:

You can click on the toggle to activate then press the run button or select interval, which can also be defined when serving