Writing Deploys¶

The definitive guide to writing pyinfra deploys.

What is a pyinfra deploy?: A deploy represents a collection of inventory (hosts to target), data (configuration, templates, files) and operations (changes/state to apply to the inventory). Deploys are written in standard Python, and other packages can be used as needed.

Layout¶

*.py - top-level operations
inventories/*.py - groups of hosts and individual host data
group_data/*.py - arbitrary data for host groups
templates/*.j2 - jinja2 template files
files/* - normal/non-template files
tasks/*.py - operations to perform a specific task
config.py - optional configuration and hooks

Inventory¶

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

# inventories/production.py

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

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

In addition to the groups defined in the inventory, all the hosts are added to two more groups: “all” and the name of the inventory file, in this case “production”. Both can be overriden by defining them in the inventory.

Data¶

Data allows you to separate deploy variables from the deploy script. With data per host and per group, you can easily build deploys that satisfy multiple environments. The data example deploy shows this in action.

Host Data¶

Arbitrary data can be assigned in the inventory and used at deploy-time. You just pass a tuple (hostname, data) instead of just the hostname:

# inventories/production.py

app_servers = [
    'app-1.net',
    ('app-2.net', {'some_key': True})
]

Group Data¶

Group data files can be used to attach data to groups of host. They are placed in group_data/<group_name>.py. This means group_data/all.py can be used to attach data to all hosts.

Data files are just Python, any core types will be included:

# group_data/production.py

app_user = 'myuser'
app_dir = '/opt/myapp'

Authenticating with Data¶

Instead of passing --key, --user, etc to the CLI, or running a SSH agent, you can define these details within host and group data. The attributes available:

ssh_port = 22
ssh_user = 'ubuntu'
ssh_key = '~/.ssh/some_key'
ssh_key_password = 'password for key'
# ssh_password = 'Using password authorization is bad. Preferred option is ssh_key.'

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.

Operations¶

Now that you’ve got an inventory of hosts and know how to authenticate with them, you can start writing operations. Operations are used to describe changes to make to the systems in the inventory. Operations are namespaced and imported from pyinfra.operations.

For example, this deploy will ensure that user “pyinfra” exists with home directory /home/pyinfra, and that the /var/log/pyinfra.log file exists and is owned by that user.

# deploy.py

# Import pyinfra modules, each containing operations to use
from pyinfra.operations import server, files

server.user(
    name='Create pyinfra user',
    user='pyinfra',
    home='/home/pyinfra',
)

files.file(
    name='Create pyinfra log file',
    path='/var/log/pyinfra.log',
    user='pyinfra',
    group='pyinfra',
    permissions='644',
    sudo=True,
)

# Execute with: pyinfra my-server.net deploy.py

Uses the server module and files module. You can see all available operations in the operations index.

Note

Pass a set object as the first argument to name the operation (as above), which will appear during a deploy. By default the operation module, name and arguments are shown.

Global Arguments¶

In addition to each operations having its own arguments, there are a number of keyword arguments available for all operations:

Privilege & user escalation:

sudo: Execute/apply any changes with sudo.
sudo_user: Execute/apply any changes with sudo as a non-root user.
use_sudo_login: Execute sudo with a login shell.
use_sudo_password: Whether to use a password with sudo (will ask).
preserve_sudo_env: Preserve the shell environment when using sudo.
su_user: Execute/apply any changes with su.
use_su_login: Execute su with a login shell.

Operation control:

name: Name of the operation
shell_executable: The shell to use. Defaults to sh (Unix) or cmd (Windows).
env: Dictionary of environment variables to set.
ignore_errors: Ignore errors when executing the operation.
success_exit_codes=[0]: List of exit codes to consider a success
timeout: Timeout for each command executed during the operation.
get_pty: Whether to get a pseudoTTY when executing any commands.
stdin: String or buffer to send to the stdin of any commands

Operation execution:

parallel: Run this operation in batches of hosts.
run_once: Only execute this operation once, on the first host to see it.
serial: Run this operation host by host, rather than in parallel.

Callbacks:

on_success: Callback function to execute on success.
on_error: Callback function to execute on error.

Using Data¶

Adding data to inventories was described above - you can access it within a deploy on host.data:

from pyinfra import host
from pyinfra.operations import server

# Ensure the state of a user based on host/group data
server.user(
    name='Setup the app user',
    user=host.data.app_user,
    home=host.data.app_dir,
)

Operation Meta¶

Operation meta can be used during a deploy to change the desired operations:

from pyinfra.operations import server

# Run an operation, collecting its meta output
create_user = server.user(
    name='Create user myuser',
    user='myuser',
}

# If we added a user above, do something extra
if create_user.changed:
    server.shell( # add user to sudo, etc...

Facts¶

Facts allow you to use information about the target host to change the operations you use. A good example is switching between apt & yum depending on the Linux distribution. Like data, facts are accessed using host.fact:

from pyinfra import host
from pyinfra.operations import yum

if host.fact.linux_name == 'CentOS':
    yum.packages(
        name='Install nano via yum',
        packages=['nano'],
        sudo=True
    )

Some facts also take a single argument like the directory or file facts. The facts index lists the available facts and their arguments.

Includes¶

Including files can be used to break out operations into multiple files, often referred to as tasks. Files can be included using local.include.

from pyinfra import local

# Include & call all the operations in tasks/install_something.py
local.include('tasks/install_something.py')

See more in examples: groups & roles.

Config¶

There are a number of configuration options for how deploys are managed. These can be defined at the top of a deploy file, or in a config.py alongside the deploy file. See the full list of options & defaults.

# config.py or top of deploy.py

# SSH connect timeout
CONNECT_TIMEOUT = 1

# Fail the entire deploy after 10% of hosts fail
FAIL_PERCENT = 10

Note

When added to config.py (vs the deploy file), these options will take effect for any CLI usage (ie pyinfra host exec -- 'tail -f /var/log/syslog').