Creating State data with Pyobjects

A high level Pythonic API

Evan Borgstrom

#SaltConf15

Site Reliability, LinkedIn

Pyobjects?

• It’s an alternative renderer for your state data

• High level “Pythonic” API

• Part of SaltStack since 2014.7.0

Context

• Long time user & contributor

• Ended up with a very large state tree and

became frustrated with YAML + Jinja

• Began initial brainstorming late 2013

• Finally inspired to start on Pyobjects at SaltConf

2014

Motivation

• 6500+ lines over

hundreds of states

(plus pillars)

• YAML no longer felt

like markup due to all

of the Jinja syntax

Not markup anymore

+

#!py

Basics

Batteries available

• Fully fledged Python environment

• Import whatever you need to compile your data

• Here be dragons:

– Blocking operations

– Monkey patching (gevent, etc)

No boilerplate

• Built-in run() function takes care of collecting and

returning data.

• No need to import import anything from

Pyobjects, everything is included

• Should be as natural as writing YAML

State objects

• One per State available on the minion

• CapWords version of the name

– file -> File

– postgres_user -> PostgresUser

– ssh_known_hosts -> SshKnownHosts

• Exposes each state function as a function

– File.managed, Pkg.installed, etc…

Using State objects

Including

• include() function takes a variable number of

arguments

• One per state to include

• Can include any state, not just pyobjects

Extending

• The extend() function is used in place of the ID

being passed to the state.

• Works exactly the same as the extend

declaration in YAML

Importing

• State trees will eventually become complex

enough that you’ll want to create reusability

• Pyobjects provides an augmentation to the import

statement to allow salt:// URIs

Context Managers / Requisites

Convenience Objects

Maps

Maps 101

Targeting using grains

• Preferred way of building configuration

• Allows for dynamically changing values without

conditionals

• Matches against the inner class name

• The grain defaults to os_family

– Add __grain__ to the class to change it

Merging with Pillar data

• Often times you’ll want to change configuration

under some special conditions

• Pillars provide the perfect platform for this

• Specify the pillar name in the merge attribute in

the main class

Best Practices

Pyobjects compliments YAML

• Pyobjects only makes sense when you need to

introduce logic into your state generation

• YAML should still be used when do you need

programmatic functions

Move logic out of templates

Pillars + Maps

• Maps provide default values for all of your

baseline settings

• Pillars allow customization using Salt’s targeting

system

• Keeps all of the configuration with the code

Future improvements

Lazy loading of modules

• The loader is lazy (pull #20274)

• Pyobjects triggers loading of all state modules

• Execution time on busy minions can be

decreased

Reactor files

• Reactor files are prime candidates to benefit from

the separation of logic & presentation

• Need to support the Local, Runner & Wheel

prefixes in a Pythonic way

Map support for complex Grains

• Currently Grains are limited to matching against

the syntax supported by Python class names

• Will be adding support through another “dunder”

attribute that allows for complex grain matching

– All numbers

– Patterns

FIN.

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