Restarting network interfaces that have changed with ansible

Question

I've got an ansible role that

- name: add virtual interface configs for vlan
  template: src=ifcfg-eth.vlan.j2 dest=/etc/sysconfig/network-scripts/ifcfg-{{ item.device }}
  with_items: "{{ vlan_interfaces }}"
  tags:  firewall_d-public-network-vlans
  notify: restart vlan interfaces

and a handler that handles it

- name: restart vlan interfaces
  command: bash -c "ifdown {{ item.device }} && ifup {{ item.device}}"
  with_items: "{{ vlan_interfaces }}"

But I don't want to start and stop all the interfaces, only the ones that have actually changed.

Is there a way to only push "item.device" to a list I can use in the handler or is there a way to make a handlers to run on each item?

Solution

So, you can't really do something specific on the playbook to handle each call in the with-items tasks. But you do get results that you can register and then do stuff with in the handler.

so add the "register" command to the task

- name: add virtual interface configs for vlan
  template: src=ifcfg-eth.vlan.j2 dest=/etc/sysconfig/network-scripts/ifcfg-{{ item.device }}
  with_items: "{{ vlan_interfaces }}"
  tags:  firewall_d-public-network-vlans
  register: add_virtual_interface_output
  notify: restart vlan interfaces

and loop through it in the handler. Because output looks like this:

    "results": [
        {
            "_ansible_notify": [
                "restart vlan interfaces"
            ],
            "changed": false,
            "gid": 0,
            "group": "root",
            "item": {
                "device": "eth1.405",
                "ipaddr": "172.16.55.5",
                "lladr": "00:50:56:ab:5d:7c",
                "network": "172.16.55.0",
                "prefix": 24
            },
            "mode": "0644",
            "owner": "root",
            "path": "/etc/sysconfig/network-scripts/ifcfg-eth1.405",
            "secontext": "system_u:object_r:net_conf_t:s0",
            "size": 100,
            "state": "file",
            "uid": 0
        },
         ...
        ] 

you can check for the "changed" state in each result, and only restart those:

- name: restart vlan interfaces
# debug : msg="{{ item.changed }}"
  command: bash -c "ifdown {{ item.item.device }} && ifup {{ item.item.device }}"
  when: item.changed == true
  with_items: "{{ add_virtual_interface_output.results }}"