"--limit" option when calling playbook in Ansible python api

Question

I am trying run playbook from withing python code however I do not know how to pass --limit option. It's similar to following How to set "--limit" option in Ansible playbook api ,however I think API has changed a bit. I have following inventory:

[rhosts]
host_a
host_b
host_c

Inside ping.yaml hosts is set rhosts but i need to limit it to only run on host_a,host_c

This is my code to run the playbook

from ansible import context
from ansible.cli import CLI
from ansible.module_utils.common.collections import ImmutableDict
from ansible.executor.playbook_executor import PlaybookExecutor
from ansible.parsing.dataloader import DataLoader
from ansible.inventory.manager import InventoryManager
from ansible.vars.manager import VariableManager
from simple_term_menu import TerminalMenu

INVENTORY_FILE = 'hosts'

loader = DataLoader()

context.CLIARGS = ImmutableDict(tags={}, listtags=False, listtasks=False, 
                    listhosts=False, syntax=False, connection='ssh',
                    module_path=None, forks=100, private_key_file=None,
                    ssh_common_args=None, ssh_extra_args=None, sftp_extra_args=None, 
                    scp_extra_args=None, become=True, become_method='sudo', become_user='root', 
                    verbosity=True, check=False, start_at_task=None,)

inventory = InventoryManager(loader=loader, sources=[INVENTORY_FILE])

variable_manager = VariableManager(loader=loader, inventory=inventory, version_info=CLI.version_info(gitinfo=False))

pbex = PlaybookExecutor(playbooks=['ping.yml'], 
                inventory=inventory, variable_manager=variable_manager, 
                loader=loader, passwords={})

results = pbex.run()

I tried to search in Ansible code and only found

def get_host_list(inventory, subset, pattern='all'):

        no_hosts = False
        if len(inventory.list_hosts()) == 0:
            # Empty inventory
            if C.LOCALHOST_WARNING and pattern not in C.LOCALHOST:
                display.warning("provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'")
            no_hosts = True

        inventory.subset(subset)

        hosts = inventory.list_hosts(pattern)
        if not hosts and no_hosts is False:
            raise AnsibleError("Specified hosts and/or --limit does not match any hosts")

        return hosts

I am can't work out what and where to pass it, if that's the right bit of code.

Answer 1

I just gave a try with ansible 2.16.2, and It works on my side with a few tweaks.

This is my code :

from ansible import context
from ansible.cli import CLI
from ansible.module_utils.common.collections import ImmutableDict
from ansible.executor.playbook_executor import PlaybookExecutor
from ansible.parsing.dataloader import DataLoader
from ansible.inventory.manager import InventoryManager
from ansible.vars.manager import VariableManager
from ansible.plugins.loader import init_plugin_loader

INVENTORY_FILE = 'hosts'

loader = DataLoader()

context.CLIARGS = ImmutableDict(tags={}, listtags=False, listtasks=False, 
                    listhosts=False, syntax=False, connection='ssh',
                    module_path=None, forks=100, private_key_file=None,
                    ssh_common_args=None, ssh_extra_args=None, sftp_extra_args=None, 
                    scp_extra_args=None, become=True, become_method='sudo', become_user='root', 
                    verbosity=True, check=False, start_at_task=None, subset='emptygroup',)

init_plugin_loader([])

inventory = InventoryManager(loader=loader, sources=[INVENTORY_FILE])

variable_manager = VariableManager(loader=loader, inventory=inventory, version_info=CLI.version_info(gitinfo=False))

CLI.get_host_list(inventory, context.CLIARGS['subset'])

pbex = PlaybookExecutor(playbooks=['ping.yml'], 
                inventory=inventory, variable_manager=variable_manager, 
                loader=loader, passwords={})

results = pbex.run()

You will notice that :

• A subset keywork is used in context.CLIARGS definition. Its value matches the --limit parameter when directly given to ansible-playbook CLI.
• The get_host_list static method of CLI class is invoked between inventory definition and playbook executor instanciation. You can find it in ansible source code here : https://github.com/ansible/ansible/blob/v2.16.2/lib/ansible/cli/playbook.py#L145. It is a wrapper for calling the subset method of InventoryManager class. Source code here : https://github.com/ansible/ansible/blob/v2.16.2/lib/ansible/cli/__init__.py#L582
• I needed to initialize the plugin loader. This is not related to your issue, but apparently it is now needed to allow the collection finder (which is instanciated during your run) to use context.CLIARGS.

When I run this python code, the subset='emptygroup' does not match any host in my inventory, and ansible only output this :

PLAY [A play] *********************************************************************************************************************************************
skipping: no hosts matched

PLAY RECAP ************************************************************************************************************************************************