Running tasks on dynamically collected EC2 instances - amazon-ec2

Question

I'm trying to write a role with tasks that filters out several EC2 instances, adds them to the inventory and then stops a PHP service on them.
This is how far I've gotten, the add_host idea I'm copying from here: http://docs.catalystcloud.io/tutorials/ansible-create-x-servers-using-in-memory-inventory.html
My service task does not appear to be running on the target instances but instead on the host specified in the playbook which runs this role.
---
- name: Collect ec2 data
connection: local
ec2_remote_facts:
region: "us-east-1"
filters:
"tag:Name": MY_TAG
register: ec2_info
- name: "Add the ec2 hosts to a group"
add_host:
name: "{{ item.id }}"
groups: foobar
ansible_user: root
with_items: "{{ ec2_info.instances }}"
- name: Stop the service
hosts: foobar
become: yes
gather_facts: false
service: name=yii-queue#1 state=stopped enabled=yes
UPDATE: when I try baptistemm's suggestion, I get this:
PLAY [MAIN_HOST_NAME] ***************************
TASK [ec2-manage : Collect ec2 data]
*******************************************
ok: [MAIN_HOST_NAME]
TASK [ec2-manage : Add the hosts to a new group]
*******************************************************
PLAY RECAP **********************************************************
MAIN_HOST_NAME : ok=1 changed=0 unreachable=0 failed=0
UPDATE #2 - yes, the ec2_remote_tags filter does return instances (using the real tag value not the fake one I put in this post). Also, I have seen ec2_instance_facts but I ran into some issues with that (boto3 required although I have a workaround there, still I'm trying to fix the current issue first).

Answer 1

If you want to play tasks on a group of targets you need to define a new play after you created the in-memory list of targets with add_host (as mentionned in your link). So to do that you need like this:
… # omit the code before
- name: "Add the ec2 hosts to a group"
add_host:
name: "{{ item.id }}"
groups: foobar
ansible_user: root
with_items: "{{ ec2_info.instances }}"
- hosts: foobar
gather_facts: false
become: yes
tasks:
- name: Stop the service
hosts: foobar
service: name=yii-queue#1 state=stopped enabled=yes