What to do when a package is needed to perform an operation preparation?

[sfermigier]

I have a deploy script that fails on a pristine server, because I have some Postgres-related operations that can't be prepared until the postgres package is installed:

# file: debug.py
from pyinfra import config
from pyinfra.operations import apt, postgresql

config.SUDO = True

apt.update(cache_time=3600)
apt.packages(packages=["postgresql"], update=True)
postgresql.role("testdb", password="testdb", _sudo_user="postgres")
postgresql.database("testdb", owner="testdb", _sudo_user="postgres")

Run with:

pyinfra @vagrant debug.py

Result:

--> Loading config...

--> Loading inventory...
    Getting Vagrant config...

--> Connecting to hosts...
    [@vagrant/default] Connected

--> Preparing Operations...
    Loading: debug.py
    [@vagrant/default] sudo: unknown user postgres
    [@vagrant/default] sudo: error initializing audit plugin sudoers_audit
    [@vagrant/default] Error: could not load fact: postgresql.PostgresqlRoles psql_host=None, psql_password=None, psql_port=None, psql_user=None
--> pyinfra error: No hosts remaining!

I believe this to be a common use case. Is there a workaround?

[sfermigier]

I found a workaround, which basically amounts to:

def deploy():
    """Deploy the app."""
    users = host.get_fact(Users)

    if "postgres" in users:
        prep_server_stage1()
        prep_server_stage2()
        prepare_app()
        install_app()
        restart_app()
    else:
        prep_server_stage1()

where prep_server_stage1() installs the postgres package (among other things) and prep_server_stage2() configures Postgres as wanted.

But there are a couple of drawbacks:

1. The script must be run twice (initially).
2. It's specific and needs to be adapted on a case-by-case basis.