worker_counts=0 disables Landscape services instead of maximizes resource usage like the charm config says

There doesn't appear to be any check for a zero value when the charm starts up and ingests its config:

# charm.py
def _start_services(self) -> bool:
        """
        Starts all Landscape Server systemd services. Returns True if
        successful, False otherwise.
        """
        self.unit.status = MaintenanceStatus("Starting services")
        is_leader = self.unit.is_leader()
        deployment_mode = self.model.config.get("deployment_mode")
        is_standalone = deployment_mode == "standalone"

        update_default_settings(
            {
                "RUN_ALL": "no",
                "RUN_APISERVER": str(self.model.config["worker_counts"]),
                "RUN_ASYNC_FRONTEND": "yes",
                "RUN_JOBHANDLER": "yes",
                "RUN_APPSERVER": str(self.model.config["worker_counts"]),
                "RUN_MSGSERVER": str(self.model.config["worker_counts"]),
                "RUN_PINGSERVER": str(self.model.config["worker_counts"]),
                "RUN_CRON": "yes" if is_leader else "no",
                "RUN_PACKAGESEARCH": "yes" if is_leader else "no",
                "RUN_PACKAGEUPLOADSERVER": (
                    "yes" if is_leader and is_standalone else "no"
                ),
                "RUN_PPPA_PROXY": "no",
            }
        )

Nor in the method that writes out the defaults file, which just writes k=v for each line:

# settings_files.py
def update_default_settings(updates: dict) -> None:
    """
    Updates the Landscape Server default settings file.

    This file is mainly used to determine which services should be
    running for this installation.
    """
    with open(DEFAULT_SETTINGS, "r") as settings_fp:
        new_lines = []

        for line in settings_fp:
            if "=" in line and line.split("=")[0] in updates:
                key = line.split("=")[0]
                new_line = f'{key}="{updates[key]}"\n'
            else:
                new_line = line

            new_lines.append(new_line)

    with open(DEFAULT_SETTINGS, "w") as settings_file:
        settings_file.write("".join(new_lines))

Documentation should be updated as this functionality doesn't appear to be implemented anywhere. As an interim fix, zero could just be turned into 1 or yes, but actual autoscaling/resource maximization would require a new charm feature.

We ended up changing the value to 1 for now. Thanks for looking into this!