Ansible - How to extract specific keys from a List of Dictionary by iterating through another List [edit] - ansible

Question

I have a list of server names and a List of dicts for all clusters in an environment. The List of dictionaries contains the relevant servers in that cluster. e.g.
"full_cluster_dict": [
{
"key": "cluster_a",
"value": [
"ca_server1",
"ca_server2",
"ca_server3",
"ca_server4",
"ca_server5",
"ca_server6",
"ca_server7",
"ca_server8"
]
},
{
"key": "cluster_b",
"value": [
"cb_server1",
"cb_server2",
"cb_server3"
]
},
{
"key": "cluster_c",
"value": [
"cc_server1",
"cc_server2",
"cc_server3",
"cc_server4"
]
}
and
"server_list": [
"ca_server1",
"cb_server2",
"ca_server6"
]
I would like to create a smaller list of dicts showing only clusters that contain servers from server_list . e.g.
"needed_cluster_dict": [
{
"key: "cluster_a",
"value": [
"ca_server1",
"ca_server2",
"ca_server3",
"ca_server4",
"ca_server5",
"ca_server6",
"ca_server7",
"ca_server8"
]
},
{
"key": "cluster_b",
"value" : [
"cb_server1",
"cb_server2",
"cb_server3"
]
}
]
I tried the following
- name: extract only relevant clusters based on the list of servers
ansible.builtin.set_fact:
needed_cluster_dict: "{{ needed_cluster_dict|d({}) | combine({item: cluster_filter}) }}"
with_items: "{{ server_list }}"
vars:
cluster_filter: "{{ sds_dict|dict2items|json_query(_query) }}"
_query: '[?value.contains(#, `{{ item }}`)].value'`
but this only returns a dictionary where the server names above are the keys and each key contains a list of servers e.g.
needed_cluster_list: {
"ca_server1: [
"ca_server1",
"ca_server2",
"ca_server3",
"ca_server4"
],
"ca_server2: [
"ca_server1",
"ca_server2",
"ca_server3",
"ca_server4"
],
...
...
}
Apologies for the edit from my original question but after asking, i discovered it's easier to loop through a list of Dictionaries than it is to loop through a Dictionary.

Answer 1

Given the list full_cluster_list (erroneously marked as dictionary full_cluster_dict in the question)
full_cluster_list:
- key: cluster_a
value:
- ca_server1
- ca_server2
- ca_server3
- ca_server4
- ca_server5
- ca_server6
- ca_server7
- ca_server8
- key: cluster_b
value:
- cb_server1
- cb_server2
- cb_server3
- key: cluster_c
value:
- cc_server1
- cc_server2
- cc_server3
- cc_server4
Convert the list to a dictionary
full_cluster_dict: "{{ full_cluster_list|items2dict }}"
gives the dictionary used in the answer below
full_cluster_dict:
cluster_a:
- ca_server1
- ca_server2
- ca_server3
- ca_server4
- ca_server5
- ca_server6
- ca_server7
- ca_server8
cluster_b:
- cb_server1
- cb_server2
- cb_server3
cluster_c:
- cc_server1
- cc_server2
- cc_server3
- cc_server4
Q: "Extract specific keys from a list of dictionaries."
A: Create a list of needed clusters. Test the intersection of the lists
needed_cluster_str: |
[{% for k,v in full_cluster_dict.items() %}
{% if v|intersect(server_list)|length > 0 %}
{{ k }},
{% endif %}
{% endfor %}]
needed_cluster: "{{ needed_cluster_str|from_yaml }}"
gives
needed_cluster:
- cluster_a
- cluster_b
Extract the needed lists
needed_cluster_lists: "{{ needed_cluster|map('extract', full_cluster_dict)|list }}"
gives
needed_cluster_lists:
- - ca_server1
- ca_server2
- ca_server3
- ca_server4
- ca_server5
- ca_server6
- ca_server7
- ca_server8
- - cb_server1
- cb_server2
- cb_server3
Create the dictionary
needed_cluster_dict: "{{ dict(needed_cluster|zip(needed_cluster_lists)) }}"
gives
needed_cluster_dict:
cluster_a:
- ca_server1
- ca_server2
- ca_server3
- ca_server4
- ca_server5
- ca_server6
- ca_server7
- ca_server8
cluster_b:
- cb_server1
- cb_server2
- cb_server3
Example of a complete playbook for testing
- hosts: localhost
vars:
server_list: [ca_server1, cb_server2, ca_server6]
full_cluster_dict:
cluster_a:
- ca_server1
- ca_server2
- ca_server3
- ca_server4
- ca_server5
- ca_server6
- ca_server7
- ca_server8
cluster_b:
- cb_server1
- cb_server2
- cb_server3
cluster_c:
- cc_server1
- cc_server2
- cc_server3
- cc_server4
needed_cluster_str: |
[{% for k,v in full_cluster_dict.items() %}
{% if v|intersect(server_list)|length > 0 %}
{{ k }},
{% endif %}
{% endfor %}]
needed_cluster: "{{ needed_cluster_str|from_yaml }}"
needed_cluster_lists: "{{ needed_cluster|map('extract', full_cluster_dict)|list }}"
needed_cluster_dict: "{{ dict(needed_cluster|zip(needed_cluster_lists)) }}"
tasks:
- debug:
var: needed_cluster
- debug:
var: needed_cluster_lists
- debug:
var: needed_cluster_dict