Inventory & Data

A pyinfra inventory provides hosts, groups and data. Host are the targets pyinfra will execute commands or state changes on (think a SSH daemon on a server, a Docker container or the local machine). Hosts can be attached to groups, and data can then be assigned to both the groups of hosts and individual hosts.

By default pyinfra assumes hosts are SSH servers and the name of the host is used as the SSH hostname. Prefixing the name of the host with @<connector-name> is used to activate alternative connectors. See: Connectors Index.

Inventory Files

Inventory files contain groups of hosts. Groups are defined as a list. For example, this inventory creates two groups, app_servers and db_servers:

app_servers = [
    "app-1.net",
    "app-2.net"
]

db_servers = [
    "db-1.net",
    "db-2.net",
    "db-3.net",
]

If you save this file as inventory.py, you can then use it in when executing pyinfra:

pyinfra inventory.py OPERATIONS...

Note

In addition to the groups defined in the inventory, all the hosts are added to a group with the name of the inventory file (eg production.py becomes production).

Limiting inventory at runtime

It is possible to limit the inventory at execution time using the --limit argument. This makes pyinfra only execute operations against targets matching the limit. Multiple limits can be provided and a limit may refer to a group or glob-style match against host names. A few examples:

# Only execute against @local
pyinfra inventory.py deploy.py --limit @local

# Only execute against hosts in the `app_servers` grouo
pyinfra inventory.py deploy.py --limit app_servers

# Only execute against hosts with names matching db*
pyinfra inventory.py deploy.py --limit "db*"

# Combine multiple limits
pyinfra inventory.py deploy.py --limit app_servers --limit db-1.net

Host Data

Data can be assigned to individual hosts in the inventory by using a tuple (hostname, data_dict):

app_servers = [
    ("app-1.net", {"install_postgres": False}),
    ("db-1.net", {"install_postgres": True}),
]

This can then be used in operations files:

from pyinfra import host

if host.data.get("install_postgres"'):
    apt.packages(
        packages=["postgresql-server"],
    )

Group Data Files

Group data can be stored in separate files under the group_data directory (there’s also a --group-data $DIR flag). Files will be loaded that match group_data/<group_name>.py, and all hosts in any matching group will receive variables defined in the file as data:

app_user = "myuser"
app_dir = "/opt/pyinfra"

These can then be used in operations:

from pyinfra import host

git.repo(
    src="git@github.com:Fizzadar/pyinfra.git",
    dest=host.data.app_dir,
    user=host.data.app_user,
)

Note

The group_data directory is relative to the current working directory. This can be changed at runtime via the --chdir flag.

Data Hierarchy

The same keys can be defined for host and group data - this means we can set a default in all.py and override it on a group or host basis. When accessing data, the first match in the following is returned:

  • “Override” data passed in via CLI args
  • Host data as defined in the inventory file
  • Normal group data
  • “all” group data

Note

pyinfra contains a debug-inventory command which can be used to explore the data output per-host for a given inventory/deploy, ie pyinfra inventory.py debug-inventory.

Connecting with Data

Data can be used to configure connectors, for example setting SSH connection details can be done like so:

ssh_user = "ubuntu"
ssh_key = "~/.ssh/some_key"
ssh_key_password = "password for key"

The Connectors Index contains full details of which data keys are available in each connector.

Global Arguments with Data

Data can also provide default values for Global Arguments, for example:

_sudo = True
_sudo_user = "pyinfra"

External Sources for Data

Because pyinfra is configured in Python, you can pull in data from pretty much anywhere just using other Python packages.