@Marvin I have a process work pool, and I want to copy an environment variable into each worker. How do I do that/

✅ thought for 692.3 seconds

the same value?

Yeah - it's just a prototype at the moment

you can set in the

env

on the one work pool, all workers will use that base job template

To clarify: The parent process that runs prefect worker start --pool <whatever> knows the value, but I don't know it in advance to put in the prefect.yaml file.

you don't need to put it in the

prefect.yaml

, you can put it in here and mutate it via UI or SDK at any time

Can I reference a secret there?

if you trust your wherever the work pool record is stored (prefect cloud, your server). if you don't want to trust it then you can give it to the worker process (because it happens to be a process worker) but in general you could always put the name of a secret you load at runtime in

env

instead of the plaintext value

Great question. In Prefect 3.x, there are two related but different targets for environment variables. Which one do you want? 1) Ensure each worker process has an environment variable - Start the worker with the variable set in its shell environment:

export MY_VAR="foo"
  prefect worker start -p my-process-pool

or

MY_VAR="foo" prefect worker start -p my-process-pool

- If you use a service manager (e.g., systemd), set it there so every worker inherits it:

[Service]
  Environment=MY_VAR=foo
  ExecStart=/usr/local/bin/prefect worker start -p my-process-pool

2) Ensure every flow run launched by the process workers gets the variable - Define it in the pool/deployment job variables so the worker passes it into each subprocess: - In prefect.yaml:

deployments:
      - name: my-deployment
        entrypoint: flows/my_flow.py:flow
        work_pool:
          name: my-process-pool
          job_variables:
            env:
              MY_VAR: "{{ $MY_VAR }}"

This “copies” the worker’s environment variable

MY_VAR

into the flow run environment. The

{{ $ENV_VAR }}

syntax references environment variables at runtime. See prefect.yaml guide and customize job variables. - Or set it at the work pool level by editing the base job template to include a default env: 1) Get the default template:

prefect work-pool get-default-base-job-template --type process --file base-job-template.json

2) Edit

base-job-template.json

to add:

{
  "job_configuration": {
    "env": {
      "MY_VAR": "{{ $MY_VAR }}"
    }
  }
}

3) Update the pool:

prefect work-pool update "my-process-pool" --base-job-template base-job-template.json

Docs: prefect work-pool CLI Notes - Using

{{ $MY_VAR }}

lets you “copy” the worker host’s environment variable into the flow run’s environment at runtime. - If you just need a constant value for all runs, you can set

env.MY_VAR: "foo"

instead of templating. Quick check: Do you want the variable set on the worker processes themselves, on every flow run they execute, or both? I can tailor the exact steps based on your setup (local shell, systemd, containers, etc.).