best way to modify json in ansible - json

Question

I have a variable (via set_fact) containing a json string:
{
"PolicyVersion": {
"CreateDate": "2017-08-07T02:48:05Z",
"Document": {
"Statement": [
{
"Action": "sts:AssumeRole",
"Effect": "Allow",
"Resource": [
"arn:aws:iam::123456789123:role/Root_Update_svcacct",
"arn:aws:iam::123456789123:role/Root_Delete_svcacct",
"arn:aws:iam::123456789123:role/Root_Create_svcacct",
"arn:aws:iam::123456789123:role/Root_Full_svcacct",
"arn:aws:iam::987654321987:role/Member1_Create_svcacct",
"arn:aws:iam::987654321987:role/Member1_Update_svcacct",
"arn:aws:iam::987654321987:role/Member1_Delete_svcacct",
"arn:aws:iam::987654321987:role/Member1_Full_svcacct"
]
}
],
"Version": "2012-10-17"
},
"IsDefaultVersion": true,
"VersionId": "v2"
}
}
What is the best way to insert more elements in the "Resource" array?
"arn:aws:iam::001122334455:role/Member1_Create_svcacct",
"arn:aws:iam::001122334455:role/Member1_Update_svcacct",
"arn:aws:iam::001122334455:role/Member1_Delete_svcacct",
"arn:aws:iam::001122334455:role/Member1_Full_svcacct"
I am exploring dumping the variable to a file and inserting the block I want with external shell tools, which does not seem to be elegant.

Answer 1

I don't know about the best way, but one option is to write a simple library module to handle the mechanics of the update for you. You could use the jsonpointer module as a way of locating the data you wish to modify, and then return the modified object to ansible. A starting point might look like:
#!/usr/bin/python
from ansible.module_utils.basic import AnsibleModule
import json
try:
import jsonpointer
except ImportError:
jsonpointer = None
def main():
module = AnsibleModule(
argument_spec=dict(
data=dict(required=True, type='dict'),
pointer=dict(required=True),
action=dict(required=True,
choices=['append', 'extend', 'update']),
update=dict(type='dict'),
extend=dict(type='list'),
append=dict(),
),
supports_check_mode=True,
)
if jsonpointer is None:
module.fail_json(msg='jsonpointer module is not available')
action = module.params['action']
data = module.params['data']
pointer = module.params['pointer']
if isinstance(data, str):
data = json.loads(str)
try:
res = jsonpointer.resolve_pointer(data, pointer)
except jsonpointer.JsonPointerException as err:
module.fail_json(msg=str(err))
if action == 'append':
res.append(module.params['append'])
if action == 'extend':
res.extend(module.params['extend'])
elif action == 'update':
res.update(module.params['update'])
module.exit_json(changed=True,
result=data)
if __name__ == '__main__':
main()
If you drop this into, e.g., library/json_modify.py, you can use it in a playbook like this:
- hosts: localhost
gather_facts: false
vars:
myvar: {
"PolicyVersion": {
"CreateDate": "2017-08-07T02:48:05Z",
"Document": {
"Statement": [
{
"Action": "sts:AssumeRole",
"Effect": "Allow",
"Resource": [
"arn:aws:iam::123456789123:role/Root_Update_svcacct",
"arn:aws:iam::123456789123:role/Root_Delete_svcacct",
"arn:aws:iam::123456789123:role/Root_Create_svcacct",
"arn:aws:iam::123456789123:role/Root_Full_svcacct",
"arn:aws:iam::987654321987:role/Member1_Create_svcacct",
"arn:aws:iam::987654321987:role/Member1_Update_svcacct",
"arn:aws:iam::987654321987:role/Member1_Delete_svcacct",
"arn:aws:iam::987654321987:role/Member1_Full_svcacct"
]
}
],
"Version": "2012-10-17"
},
"IsDefaultVersion": true,
"VersionId": "v2"
}
}
tasks:
- json_modify:
data: "{{ myvar }}"
pointer: "/PolicyVersion/Document/Statement/0/Resource"
action: extend
extend:
- "arn:aws:iam::001122334455:role/Member1_Create_svcacct"
- "arn:aws:iam::001122334455:role/Member1_Update_svcacct"
- "arn:aws:iam::001122334455:role/Member1_Delete_svcacct"
- "arn:aws:iam::001122334455:role/Member1_Full_svcacct"
register: result
- debug:
var: result.result
The result of running this playbook and the proposed module is:
TASK [debug] *******************************************************************
ok: [localhost] => {
"result.result": {
"PolicyVersion": {
"CreateDate": "2017-08-07T02:48:05Z",
"Document": {
"Statement": [
{
"Action": "sts:AssumeRole",
"Effect": "Allow",
"Resource": [
"arn:aws:iam::123456789123:role/Root_Update_svcacct",
"arn:aws:iam::123456789123:role/Root_Delete_svcacct",
"arn:aws:iam::123456789123:role/Root_Create_svcacct",
"arn:aws:iam::123456789123:role/Root_Full_svcacct",
"arn:aws:iam::987654321987:role/Member1_Create_svcacct",
"arn:aws:iam::987654321987:role/Member1_Update_svcacct",
"arn:aws:iam::987654321987:role/Member1_Delete_svcacct",
"arn:aws:iam::987654321987:role/Member1_Full_svcacct",
"arn:aws:iam::001122334455:role/Member1_Create_svcacct",
"arn:aws:iam::001122334455:role/Member1_Update_svcacct",
"arn:aws:iam::001122334455:role/Member1_Delete_svcacct",
"arn:aws:iam::001122334455:role/Member1_Full_svcacct"
]
}
],
"Version": "2012-10-17"
},
"IsDefaultVersion": true,
"VersionId": "v2"
}
}
}

Answer 2

Actually Ansible is natively able to read JSON files.
see this question:
add-a-new-key-value-to-a-json-file-using-ansible

Answer 3

This is a little bit old. I know but I felt it could be useful to many people so I'll post here my solution as "the best way to modify a json" that I could personally find.
First of all the JSON. In my use-case I had a bunch of aws snapshots that were encrypted with the wrong kms key and I had to recreate the AMI with the correct key.
So I had to :
get data of the old snapshots ( like size device_name etc.)
create the new snaps with the different key
re-register a new ami with the correct block_device_mapping
Here's the code
- name: get ami
amazon.aws.ec2_ami_info:
image_ids: ami-<id>
region: "{{ region }}"
register: ami
- name: save snapshot ids and device_name and volume_size
set_fact:
snapshot_ids: "{{ ami | json_query('images[].block_device_mappings[].ebs.snapshot_id') }}"
device_name: "{{ ami | json_query('images[].block_device_mappings[].device_name') }}"
volume_size: "{{ ami | json_query('images[].block_device_mappings[].ebs.volume_size') }}"
basically each of the above is a list of each of the 3 things (device_name, snap_id, volume_size) that I need (but it could be extended)
then:
- name: get kms arn
aws_kms_info:
filters:
alias: "{{ kms_keys.alias }}"
region: "{{ region }}"
register: aws_kms_facts_out
- debug:
var: aws_kms_facts_out
- set_fact:
kms_arn: "{{ aws_kms_facts_out['keys'][0].key_arn }}"
- name: copy snap with new encryption key
community.aws.ec2_snapshot_copy:
source_region: "{{ region }}"
region: "{{ region }}"
source_snapshot_id: "{{ item }}"
encrypted: yes
kms_key_id: "{{ kms_arn }}"
loop: "{{ snapshot_ids }}"
register: new_snapshots
and then here's the catch
- set_fact:
new_snapshot_ids: "{{ new_snapshots| json_query('snapshots[].snapshot_id') }}"
- name: creating the block_device_mappings structure (still a list of objects)
ansible.builtin.debug:
msg: '{
"device_name": "{{ item.2 }}",
"delete_on_termination": "true",
"snapshot_id": "{{ item.0 }}",
"volume_size": {{ item.1 }},
"volume_type": "gp2"
}'
loop: "{{ new_snapshot_ids|zip_longest(volume_size,device_name)|list }}"
register: block_device_mappings
- set_fact:
bdm: "{{ block_device_mappings | json_query('results[].msg') }}"
finally
- name: create new ami from newly created snapshots
amazon.aws.ec2_ami:
region: "{{ region }}"
name: "{{ instance.name }}-{{ ansible_date_time.date }}"
state: present
architecture: x86_64
virtualization_type: hvm
root_device_name: /dev/sda1
device_mapping: "{{ bdm }}"
This is how you can do it without requiring any additional trick.
Of course this is declined to my particular use case but you can adapt it to any circumstance, that do not require a complete disassemble and reassemble of the Json itself