Jinja2

Handling nasty expressions in Ansible with grace

There are inevitable moments when you need to do loop calculations in Ansible. You have a group, and you need to extract some variable from all hosts in that group (except those who don’t have this variable), and use it for iteration, or for…

Creating list in loop in Ansible

Today I found a new way to create list for set_fact within loop.

Old approach

- set_fact:
    foo: '{{ (foo|d([])).combine([{"id": hostvars[item]["ID"]}]) }}'
  loop: '{{ groups.mygroup }}'

Mapping strings into numbers in Ansible

How to make a stable mapping of a string into a numeric hash within given range, by using only Ansible and Jinja2.

How to filter a dictionary in Ansible

Let’s say you want to remove from your dictionary (object) all elements with value of empty string.

Input:

foo:
  key1: used
  key2: ""
  key3: another_used

Working with dates and times in Ansible

Ansible has some rudimentary support for dates and times, but gosh…

I got a simple task: compare string like this ’10 Apr 19 12:52 UTC’ with mtime for a given file to see if file is older than a given date.

WTF bool filter in Ansible

It’s not what you think

Jinja2 filters:

• foo|list converts foo to list
• foo|string converts foo to string
• foo|int converts foo to int

How enquote list elements

and join them by comma

How to enquote list elements

It’s a challenge for jinja-ninja. You have a list, and you want to rewrite it in a single line, each element in quotes, joined by coma. You need to handle well all…

An unexpected trap with variable_start_string/variable_end_string

There are two features of Ansible:

1. Lazy evaluation of jinja2. If you set your variable foo to ‘{{some_var}}’, it’s not set to the value of some_var, instead it become a literal…

when ‘when’ starts with a string

It’s a small post about trivial thing, but someone need to write it down.

Let’s say we have a playbook:

- foo: args=args
  when: 'foo' in bar