error

TASK: [magento | Copy Magento local.xml config] *******************************
fatal: [ansibleweb1] => {'msg': "One or more undefined variables: 'dict object' has no attribute 'ansible_eth0'", 'failed': True}
fatal: [ansibleweb1] => {'msg': "One or more undefined variables: 'dict object' has no attribute 'ansible_eth0'", 'failed': True}

group_vars_all

#interface
iface: eth0

#db_ip
mag_db_ip: "{{ hostvars['ansibledb1']['ansible_' + iface].ipv4.address }}"

#app server's IP
mag_app_ip: "{{ hostvars['ansibleweb1']['ansible_' + iface].ipv4.address }}"

local.xml.j2

<connection>
                    <host><![CDATA[{{ mag_db_ip }}]]></host>
                    <username><![CDATA[{{ mag_db_user }}]]></username>
                    <password><![CDATA[{{ mag_db_password }}]]></password>
                    <dbname><![CDATA[{{ mag_db_name }}]]></dbname>
                    <initStatements><![CDATA[SET NAMES utf8]]></initStatements>
                    <model><![CDATA[mysql4]]></model>
                    <type><![CDATA[pdo_mysql]]></type>
                    <pdoType><![CDATA[]]></pdoType>
                    <active>1</active>
                </connection>

magento.yml

---
- name: Download Magento Downloader 
  get_url: url=http://www.magentocommerce.com/downloads/assets/{{ mag_version }}/magento-{{ mag_version }}.tar.gz dest=/srv/magento-{{ mag_version }}.tar.gz

- name: Extract Archive
  command: chdir=/srv/ /bin/tar xvf magento-{{ mag_version }}.tar.gz creates=/srv/magento

- name: Change ownership of Magento installation
  file: path=/srv/magento/ owner=www-data group=www-data state=directory recurse=yes

- name: Copy Magento local.xml config
  template: src=local.xml.j2 dest=/srv/magento/app/etc/local.xml owner=www-data group=www-data

mysql.yml

---
- name: Install required packages for apt_repository
  apt: name={{ item }} state=present
  with_items:
  - python-apt
  - python-pycurl

- name: Add MySQL 5.6 PPA
  apt_repository: repo='ppa:ondrej/mysql-5.6' state=present

- name: Install Mysql package
  apt: name={{ item }} state=present
  with_items:
   - mysql-server-5.6
   - python-mysqldb

- name: Create Mysql configuration file
  template: src=my.cnf.j2 dest=/etc/mysql/my.cnf
  notify: 
  - restart mysql

- name: Start Mysql Service
  service: name=mysql state=started enabled=true

- name: Create Magento database
  mysql_db: name={{ mag_db_name }} state=present

- name: Create Magento database user
  mysql_user: name={{ mag_db_user }} password={{ mag_db_password }} priv={{ mag_db_name }}.*:ALL host={{ mag_app_ip }} state=present