How can I debug this playbook so that I can properly loop over the hostvars?

[Abe Voelker]

I have an inventory file like this:

[redisservers]
72.14.178.81

[webservers]
198.58.107.247

I'm trying to run this playbook against the redisservers group to allow access to port 6379 for the webservers:

---
- name: Allow port 6379 (Redis) access to Web servers
  ufw: rule=allow interface=eth0 direction=in port=6379 proto=tcp src="{{ hostvars[item]['ansible_eth0']['ipv4']['address'] }}"
  with_items: groups['webservers']

But I'm getting this error:

TASK: [redis | Allow port 6379 (Redis) access to Web servers] ***************** 

fatal: [72.14.178.81] => One or more undefined variables: 'dict object' has no attribute 'ansible_eth0'

FATAL: all hosts have already failed -- aborting

I'm not sure what's going on as all servers definitely have an eth0 interface.  When I run ansible all -m setup -i inventory, the output seems to confirm that there is an ansible_eth0 fact available for all servers: https://gist.github.com/abevoelker/7a3c18f10793a744e6da

I've tried simplifying the playbook to refer to the exact server in question to remove the looping:

---
- name: Allow port 6379 (Redis) access to Web servers
  ufw: rule=allow interface=eth0 direction=in port=6379 proto=tcp src="{{ hostvars[groups['webservers'][0]]['ansible_eth0']['ipv4']['address'] }}"

and also

---
- name: Allow port 6379 (Redis) access to Web servers
  ufw: rule=allow interface=eth0 direction=in port=6379 proto=tcp src="{{ hostvars['198.58.107.247']['ansible_eth0']['ipv4']['address'] }}"

But I'm still getting the same error.

Any hints as to what I'm doing wrong or how I can continue to debug this?  I'm using Ansible 1.7.1.

[Abe Voelker]

So I wrote a template task that populates this jinja template:

{{ hostvars['198.58.107.247'] }}

And this is the output I got:

{'ansible_ssh_user': 'root', 'inventory_hostname_short': '198', 'group_names': ['webservers'], 'inventory_hostname': '198.58.107.247'}

So hostvars['198.58.107.247'] doesn't seem to be filled with all the facts for that host.  Then I realized that the root playbook I'm running (provision.yml) looks like this:

---
- include: redisservers.yml
- include: webservers.yml

And the redisservers.yml playbook it includes looks like this:

---
- hosts: redisservers
  roles:
    - redis

And the full output I'm seeing from running the playbook looks like this (my emphasis):

PLAY [redisservers] *********************************************************** 

GATHERING FACTS *************************************************************** 

ok: [72.14.178.81]

TASK: [redis | Allow port 6379 (Redis) access to Web servers] ***************** 

fatal: [72.14.178.81] => One or more undefined variables: 'dict object' has no attribute 'ansible_eth0'

FATAL: all hosts have already failed -- aborting

So from the output it looks like it has only gathered facts for 72.14.178.81 by the time the redisservers playbook runs.  Therefore I fixed my issue by changing the order of provision.yml, which runs the webservers playbook first and populates the facts for 198.58.107.247 before the redisservers playbook runs:

---
- include: webservers.yml
- include: redisservers.yml

Then I figured out that if I add a hosts: all line to provision.yml, it will gather facts for all hosts before running the included playbooks:

---
- hosts: all
- include: webservers.yml
- include: redisservers.yml

PLAY [all] ******************************************************************** 

GATHERING FACTS *************************************************************** 

ok: [72.14.178.81]

ok: [198.58.107.247]

PLAY [webservers] *************************************************************

... 

So that way I don't have worry about the order of playbook inclusion.  But this still seems kind of hacky... wouldn't it be better if there were a way to access hostvars in a manner that will just populate it for a host if it hasn't been populated yet?  Sort of a lazy evaluation?

[Michael DeHaan]

In Ansible to use facts about a host you must have either:

already gathered facts from that host in that play (just gathering facts would be enough, no tasks needed)

- hosts: webservers:dbservers

  tasks: []

- hosts: webservers  # that need to know facts about dbservers

  tasks:

    - ...

OR

enabled fact caching and previously talked to that host within the cache timeout 

http://docs.ansible.com/playbooks_variables.html#fact-caching

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