Ansible - iterate over a list of dictionaries - ansible

Question

I built the following list but I don't succeed to iterate over it.
Should I use with_items? with_elements? or something else?
My goal is to iterate over all the hosts in the inventory, get their name and their IP, and finally print it.
- set_fact:
list_of_hosts: |
{% set myList = [] %}
{% for host in groups['all'] %}
{% set ignored = myList.extend([{'server_name': host, 'server_ip': hostvars[host].ansible_eth0.ipv4.address }]) %}
{% endfor %}
{{ myList }}
- debug: msg="{{ item.server_name }}"
with_items: "{{ list_of_hosts }}"
Here is my list when I debug it:
TASK [common : debug] ************************************************************************************************
ok: [my1stServer] => {
"msg": " [{'server_ip': u'192.168.0.1', 'server_name': u'my1stServer'}, {'server_ip': u'192.168.0.2', 'server_name': u'my2ndServer'}]\n"
}
And here is the error but it is not really relevant :
fatal: [my1stServer]: FAILED! => {"failed": true, "msg": "the field 'args' has an invalid value, which appears to include a variable that is undefined. The error was: 'ansible.vars.unsafe_proxy.AnsibleUnsafeText object' has no attribute 'server_name'\n\nThe error appears to have been in 'hosts.yml': line 19, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- debug: msg=\"{{ item.server_name }}\"\n ^ here\nWe could be wrong, but this one looks like it might be an issue with\nmissing quotes. Always quote template expression brackets when they\nstart a value. For instance:\n\n with_items:\n - {{ foo }}\n\nShould be written as:\n\n with_items:\n - \"{{ foo }}\"\n"}

Answer 1

Please forgive me for bluntness, but the proposed implementation makes it an effort to understand what the idea actually is. which is simple: to print some variables anyway present in hostvars[host] for a list of hosts picked by various criteria.
If we keep implementation close to that idea, implementation is simpler.
So what I'd do to create a list of hosts picked by group membership, or possibly 'hand picked' is to actually do what I just wrote :).
Consider this task list:
# this task creates an empty list
- name: create my_cool_list
set_fact:
my_cool_list: []
# this task adds to the list all hosts in groups we're iterating over
- name: update my cool list with whole groups
set_fact: '{{my_cool_list + groups[curr_grp]}}'
with_items:
- grp1
- grp2
loop_control:
loop_var: curr_grp
# this task adds to the list all hosts we're iterating over
- name: update my cool list with specific hosts
set_fact: '{{my_cool_list + [curr_node]}}'
with_items:
- node001
- node101
loop_control:
loop_var: curr_node
# now we can iterate over the list, accessing specific fields on each host
- name: go over my cool list and print ansible_init_mgr
debug:
msg: 'hostvars["{{curr_host}}"].ansible_init_mgr: {{hostvars[curr_host].ansible_init_mgr}}'
with_items: '{{my_cool_list|default([], true)|list}}'
Furthermore, you can add safety when: by validating the key you're accessing is defined..
And, to print a selection of variables about each host, you should use jinja filter map('extract',...):
- name: print some vars from each host
debug:
msg: {'server_name': '{{hostvars[curr_node]|selectattr("ansible_hostname")}}', 'ip_address': '{{hostvars[curr_node]|selectattr("ansible_eth0.ipv4.address")}}'}
with_items: '{{my_cool_list|default([], true)|list}}'
loop_control:
loop_var: curr_node
IF you want to increase readability though, you better write a filter plugin, which would do the above stuff, and hide iteration ugliness in readable way, so you can have:
Either (For generic approach, i.e. without renaming attributes)
- name: print some vars from each host
debug:
msg: '{{my_cool_list|multi_select_in_dict(["ansible_hostname", "ansible_eth0.ipv4.address")}}'
Or specific approach (so that you are using specific hard coded remapping of attributes...)
- name: print some vars from each host
debug:
msg: '{{my_cool_list|my_cool_filter}}'