Data manipulation in Ansible: json_query

The second big change in Ansible is an introduction of json_query filter in templates. It is big, because it allows to perform complicated queries without invoking slow Ansible loops. Whole data processing happens almost instantly, without cluttering output.

Data manipulation in Ansible: string transformation

It’s horrible. Kids, never do this!

I have a list (let’s say ‘data’), which contains stings. I need to add prefix and suffix to each string without involving Ansible loops (for example…

loop_control: label (Ansible)

If you iterate over huge dictionary Ansible’s output is real mess. In my case each iteration produced about 3k output, and it pushed full jenkins output way over 2Mb for my project.

Fighting with limitation of ‘|default()’ filter in jinja2 (ansible)

A very common and upsetting error:

^ here\n\nexception type: <class ‘ansible.errors.AnsibleUndefinedVariable’>\nexception: ‘dict object’ has no attribute ...

vars and with_items in a single task

Check your Ansible intuition

Quiz:

---
- hosts: all
  gather_facts: no
  tasks:
  - debug: var=baz
    with_items: '{{test}}'
    vars:
     test: '{{foo + bar}}'
     foo: [5, 6]
     baz…

Buggy timezone module in Ansible

If you ever saw this:

fatal: [server]: FAILED! => {"changed": false, "msg": "Error message:\nstill not desired state, though changes have made\nOther message(s):\nAdded 1 line and deleted 1 line(s) on /etc/timezone"}

Fallback value in Ansible

Jinja2 gave us ‘default’ filter. It works like this: ‘{{foo|default(“foo subsitute”)}}’. It works fine, but sometimes you need to check not against ‘defined/undefined’, but for ‘None’ value. Mostly it happens when you fill vars, but you have no answer for some variable at that time…

A way to transform data in Ansible

Ability to transform data for a single task is often neglected. I don’t know about everyone else, but I neglected it for long, and now catching up.

Let’s assume that we have some bulky structure, for example, users in a setup. We have…

IP math: how to fit external IP address into localhost binding

I’ve got a problem: There are unknown number of backends to listen on a localhost. Each backend will be proxy_pass’ed by nginx for separate external IP. Link between external ip and backend is rigid. The problem is to find…

Cron, anacron and the best unix we have

Computer interfaces of our ancestors bring me to the knee. Today I learned one more “amazing” of it. It called ‘cron.daily’. (hourly and so on).

Expectations: you put your scripts there and they will be executed as root every daily…