Road-to-DevOps/Pepiniere/Ansible/Formation/6.structures-de-controle.md

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![Logo Ansible](images/logo-ansible.svg)
# Structures de contrôle


## _Facts_

* Variables délivrées par le système distant :

    - Adresses IP

    - Système d'exploitation

    - ...


## Facts - module setup

* Liste des informations disponibles : module _setup_

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```none
$ ansible my-host -i ./hosts -m setup
my-host | SUCCESS => {
    "ansible_facts": {
        "ansible_all_ipv4_addresses": [
            "10.6.214.74"
        ],
        "ansible_all_ipv6_addresses": [
            "fe80::250:56ff:fe9d:1aaa"
        ],
        "ansible_architecture": "x86_64",
        ...
```


### Facts pour la gestion multi-os

* `ansible_pkg_mgr` : Le gestionnaire de paquets

* `ansible_os_family` : La famille d'OS

* `ansible_distribution` : Information détaillées sur la distribution


### Gestionnaire de paquets
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```none
$ ansible my-host -i ./hosts -m setup | grep ansible_pkg_mgr
        "ansible_pkg_mgr": "yum",
```


### Famille d'OS
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```none
$ ansible my-host -i ./hosts -m setup | grep ansible_family
        "ansible_os_family": "RedHat",
```


### Distribution
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```none
$ ansible my-host -i ./hosts -m setup | grep ansible_distribution
        "ansible_distribution": "CentOS",
        "ansible_distribution_file_parsed": true,
        "ansible_distribution_file_path": "/etc/redhat-release",
        "ansible_distribution_file_variety": "RedHat",
        "ansible_distribution_major_version": "7",
        "ansible_distribution_release": "Core",
        "ansible_distribution_version": "7.5.1804",
```


### Exemple d'aiguillage multi-OS

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Arborescence du rôle
```none
my-role
├── README.md
├── tasks
│   ├── CentOS.yaml -> RedHat.yaml
│   ├── Debian.yaml
│   ├── main.yaml
│   ├── RedHat.yaml
│   └── Ubuntu.yaml -> Debian.yaml
└── vars
    ├── CentOS-6.yaml
    ├── CentOS-7.yaml
    ├── Debian-8.yaml
    ├── Debian-9.yaml
    ├── RedHat-6.yaml
    ├── RedHat-7.yaml
    └── Ubuntu-16.yaml
```


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`my-role/tasks/main.yaml`
```yaml
- name: Add the OS specific variables
  include_vars: '{{ ansible_distribution }}-{{ ansible_distribution_major_version }}.yaml'

- include_tasks: '{{ansible_distribution}}.yaml'
```


## Utilisation des _conditionals_

* Action déclenchée de manière conditionnelle  
(en fonction du résultat d’une variable).

* Utilisation de _when_.

<small>https://docs.ansible.com/ansible/playbooks_conditionals.html</small>


### Exemple
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```yaml
- hosts: web
  tasks:
    - name: Install Apache for CentOS system
      yum:
        name: httpd
        state: present
        update_cache: yes
      when:
        - ansible_os_family == "RedHat"   # sera joué sur RedHat et Centos
    - name: Install Apache for Ubuntu system
      apt:
        name: apache2
        state: present
        update_cache: yes
      when:
        - ansible_os_family == "Debian"   # sera joué sur Debian et Ubuntu
```
Chaque tâche cible une famille  
de système d'exploitation précise.


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```none
$ ansible-playbook playbook.yaml -i ./hosts

PLAY [web] *******************************************************************

TASK [setup] *****************************************************************
ok: [centos-vm]
ok: [ubuntu-vm]

TASK [Install Apache for CentOS system] **************************************
ok: [centos-vm]
skipping: [ubuntu-vm]

TASK [Install Apache for Ubuntu system] **************************************
skipping: [centos-vm]
ok: [ubuntu-vm]

PLAY RECAP *******************************************************************
centos-vm   : ok=2   changed=0   unreachable=0   failed=0
ubuntu-vm   : ok=2   changed=0   unreachable=0   failed=0
```

Les tâches sont exécutées ou non en fonction  
de la famille du système d'exploitation.


## Utilisation des _loops_

* Boucles pour la réalisation d'actions répétitives.

* Permet de faire plusieurs actions dans une seule tâche.

* Création d'utilisateurs, installation de paquets, ...

* Utilisation de ~~with-x~~ _loop_

<small>https://docs.ansible.com/ansible/playbooks_loops.html</small>


### with-x
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Paramètre | Type | Example d'utilisation
- | - | -
`with_items` | Array | To create a group of users, directories, or to install a list of packages
`with_nested` | Nested loops | To create a list of MySQL users and grant them access to a group of databases
`with_dict` | Hashes | To parse a dictionary of key-value pairs and create virtual hosts
`with_fileglobs` |Files with pattern match | To parse a path and copy only those files that match a certain pattern
`with_together` | S ets | To join two arrays as a set and to loop over it
`with_subelements` | Hash sub element | To walk over the list of SSH keys and distribute them to a user
`with_sequence` | Integer sequence | To loop a sequence of numbers
`with_random_choice` | Random choice | To pick up items from the array in a random order
`with_indexed_items` | Array with index | Array with an index and is useful when an index for items is required


### Exemple avec with_items

```yaml
- hosts: my-host
  tasks:
    - name: Add some users
      user:
        name: "{{ item }}"
        state: present
      with_items:
        - bob
        - alice
        - joe
```

Attention ! à partir d'Ansible 2.5 _with-x_ n'est plus la méthode recommandé pour effectué des boucles.


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```none
$ ansible-playbook playbook.yaml -i ./hosts

PLAY [my-host] ***************************************************************

TASK [setup] *****************************************************************
ok: [my-host]

TASK [Add some users] ********************************************************
changed: [my-host] => (item=bob)
changed: [my-host] => (item=alice)
changed: [my-host] => (item=joe)

PLAY RECAP *******************************************************************
my-host   : ok=2   changed=1   unreachable=0   failed=0
```

La boucle a bien itéré sur les 3 utilisateurs.


### Migration vers loop

* A partir d'Ansible 2.5 _with-x_ n'est plus la méthode recommandée pour effectuer des boucles.

* La documentation sur les boucles propose une section pour aider à la migration de _with-x_ vers _loop_.

<small>https://docs.ansible.com/ansible/latest/user_guide/playbooks_loops.html</small>


### Exemple avec loop
```yaml
- hosts: my-host
  tasks:
    - name: Add some users
      user:
        name: "{{ item }}"
        state: present
      loop:
        - bob
        - alice
        - joe
```

On remplace simplement `with_items` par `loop`.


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```none
$ ansible-playbook -i inventories/formation/hosts playbook.yaml

PLAY [my-host] ***************************************************************

TASK [Gathering Facts] *******************************************************
ok: [my-host]

TASK [Add some users] ********************************************************
changed: [my-host] => (item=bob)
changed: [my-host] => (item=alice)
changed: [my-host] => (item=joe)

PLAY RECAP *******************************************************************
my-host    : ok=2    changed=1    unreachable=0    failed=0   
```

Le résultat final est strictement identique.


```yaml
- hosts: my-host
  tasks:
    - name: Add some users
      user:
        name: "{{ item.name }}"
        state: present
        groups: "{{ item.groups }}"
      loop:
        - { name: 'bob', groups: 'wheel' }
        - { name: 'alice', groups: 'root' }
        - { name: 'joe', groups: 'root' }
```

En plus des _strings_ , il est possible d'utiliser des _hashes_.


### Itérer sur l'inventaire
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```yaml
- hosts: centos7
  tasks:
    - name: Iterate on hosts in the group all in the inventory
      debug:
        msg: "{{ item }}"
      loop: "{{ groups['all'] }}"   # on itère sur les machines du groupe all
```
```none
$ ansible-playbook -i ./hosts playbook.yaml

PLAY [centos7] *****************************************************************

TASK [Iterate on hosts in the group all in the inventory] **********************
ok: [ansible-1] => (item=ansible-3) => {
    "msg": "ansible-3"
}
ok: [ansible-1] => (item=ansible-1) => {
    "msg": "ansible-1"
}
ok: [ansible-1] => (item=ansible-2) => {
    "msg": "ansible-2"
}
ok: [ansible-2] => (item=ansible-3) => {
    "msg": "ansible-3"
}
ok: [ansible-2] => (item=ansible-1) => {
    "msg": "ansible-1"
}
ok: [ansible-2] => (item=ansible-2) => {
    "msg": "ansible-2"
}
```

Chaque machine du Play (_centos7_) itère sur le groupe _all_.


### Itérer sur le Play
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```yaml
- hosts: centos7
  tasks:
    - name: Iterate on all the hosts in the current play
      debug:
        msg: "{{ item }}"
      loop: "{{ ansible_play_batch }}"   # variable qui contient les machines du Play
```
```none
$ ansible-playbook -i inventories/formation/hosts playbook.yaml

PLAY [centos7] *****************************************************************

TASK [Iterate on all the hosts in the current play] ****************************
ok: [ansible-1] => (item=ansible-1) => {
    "msg": "ansible-1"
}
ok: [ansible-1] => (item=ansible-2) => {
    "msg": "ansible-2"
}
ok: [ansible-2] => (item=ansible-1) => {
    "msg": "ansible-1"
}
ok: [ansible-2] => (item=ansible-2) => {
    "msg": "ansible-2"
}
```

Chaque machine du Play (_centos7_) itère  
sur les machines du Play (_centos7_).


## Travaux pratiques
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![Travaux pratiques](images/tp.gif)

<small>[TP Ansible : structures de contrôle](travaux-pratiques/tp-ansible-structures-de-controle.html)</small>