Ansible loop over list and collect output in a list - ansible

Question

I just don't understand how you are supposed to loop over a list and collect the results in a list in ansible:
- name: Collect all containers
command: docker ps --all --no-trunc --format {% raw %}"{{json .}}"{% endraw %}
register: docker_raw_containers
- debug:
msg: "{{ docker_raw_containers.stdout_lines }}"
- name: Convert variables
set_fact:
docker_raw_container_item: "{{ item | to_json }}"
loop: "{{ docker_raw_containers.stdout_lines }}"
- name: Convert to list
set_fact:
docker_parsed_containers: " {{ docker_raw_container_item | map(attribute='ID') | list }} "
- debug:
msg: "{{ docker_parsed_containers }}"
This code should result in a list of containers IDs and CreatedAt attributes. But it just results in a list of AnsibleUndefined objects. Where is my fault?

Answer 1

Converting a json string to an ansible variable requires the from_json filter. You used to_json which does exactly the opposite.
You can create a list all at once my mapping the from_json filter to each result line. The following playbook should meet your requirements with minimum ansible tasks.
---
- name: Parse docker ps output formated as json
hosts: all
gather_facts: false
tasks:
- name: Collect all containers
command: docker ps --all --no-trunc --format {% raw %}"{{json .}}"{% endraw %}
register: docker_raw_containers
# This is an info only command so it never changes the target
changed_when: false
- name: Convert variable
set_fact:
docker_parsed_containers: "{{ docker_raw_containers.stdout_lines | map('from_json') | list }}"
- debug:
msg: "{{ docker_parsed_containers }}"
Which gives the following result on my machine (launched some test containers for the occasion...):
$ ansible --version
ansible 2.9.2
config file = None
configured module search path = ['/home/user/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
ansible python module location = /usr/local/lib/python3.6/dist-packages/ansible
executable location = /usr/local/bin/ansible
python version = 3.6.9 (default, Nov 7 2019, 10:44:02) [GCC 8.3.0]
$ ansible-playbook test.yml
PLAY [Parse docker ps output formated as json] **************************************************************************************************************************************************************************************************************************
TASK [Collect all containers] *******************************************************************************************************************************************************************************************************************************************
ok: [localhost]
TASK [Convert variable] *************************************************************************************************************************************************************************************************************************************************
ok: [localhost]
TASK [debug] ************************************************************************************************************************************************************************************************************************************************************
ok: [localhost] => {
"msg": [
{
"Command": "\"bash -c 'while true; do sleep 20000; done'\"",
"CreatedAt": "2019-12-09 10:05:18 +0100 CET",
"ID": "9e6ea71499df19f5c1e33e069c533f43b3ec18c957b31bcca571b0a194b23027",
"Image": "python:3.8",
"Labels": "",
"LocalVolumes": "0",
"Mounts": "",
"Names": "demo2",
"Networks": "bridge",
"Ports": "",
"RunningFor": "39 minutes ago",
"Size": "0B",
"Status": "Up 39 minutes"
},
{
"Command": "\"bash -c 'while true; do sleep 20000; done'\"",
"CreatedAt": "2019-12-09 10:05:17 +0100 CET",
"ID": "038f1e4b1f4dd627f6ccea2ddce858e1055474c6a092f32c773e842e938dec68",
"Image": "python:3.8",
"Labels": "",
"LocalVolumes": "0",
"Mounts": "",
"Names": "demo1",
"Networks": "bridge",
"Ports": "",
"RunningFor": "39 minutes ago",
"Size": "0B",
"Status": "Up 39 minutes"
},
{
"Command": "\"/bin/sh -c 'virtualenv venv'\"",
"CreatedAt": "2019-12-04 18:26:14 +0100 CET",
"ID": "88427258f30226ee9ba8af420978ffb2d4046206a7b6b7dc3ee3f5494236e12b",
"Image": "sha256:8a3e76ff0da0dd43a305461f3a6bf6abd320770fb6c3c2c365b5ea1a0062de0b",
"Labels": "",
"LocalVolumes": "0",
"Mounts": "",
"Names": "cocky_brattain",
"Networks": "bridge",
"Ports": "",
"RunningFor": "4 days ago",
"Size": "0B",
"Status": "Exited (127) 4 days ago"
}
]
}
PLAY RECAP **************************************************************************************************************************************************************************************************************************************************************
localhost : ok=3 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0