为什么ansible评估剧本中未使用的变量？

Question

I am using ansible 2.3.1.1 with jenkins. I have encountered the following issue - my playbook which uses variables from aws dynamic inventory becomes extremely slow. The most interesting case that if I copy this playbook outside my jenkins workspace and run in any other directory the execution speed is OK. In order to test it I remove all variable files from workspace directory /group_vars/all - after that the execution speed for this playbook inside workspace become OK too. So, as I understand ansible calculate all variables from group_vars/all even if they are not used in current playbook. So could someone explain why ansible does so and how it could be tuned?

the playbook is the following

============

- hosts: "xxxx"

tasks:

 - name: print something
  debug:
    var: hostvars["{{item}}"]['ec2_vpc_id']
  with_items: "{{groups['some_tag']}}"

============

Answer 1

This is how thinks work in current version. Avoid hostvars .

You can track progress on this issues 23349 and 17528 .