Exploiting Jinja2 in Ansible - http://blog.keshi.org/hogememo/2015/12/07/exploiting-ansible-jinja2

basicexp-log.txt

$ ansible-playbook -i localhost, basicexp-playbook.yml

PLAY [localhost] ************************************************************** 

TASK: [OK: ['a', 'b', 'c']] *************************************************** 
ok: [localhost] => {
    "msg": [
        "a", 
        "b", 
        "c"
    ]
}

TASK: [OK: 'a,b,c'] *********************************************************** 
ok: [localhost] => {
    "msg": "a,b,c"
}

TASK: [OK: ['a', 'b']] ******************************************************** 
ok: [localhost] => {
    "msg": [
        "a", 
        "b"
    ]
}

TASK: [OK: a,b,c] ************************************************************* 
ok: [localhost] => {
    "msg": "a,b,c"
}

TASK: [NG: Sequence assignment] *********************************************** 
skipping: [localhost]

TASK: [NG: Built-in functions like len(), map()] ****************************** 
skipping: [localhost]

TASK: [NG: Expression only in {% %} statement] ******************************** 
skipping: [localhost]

TASK: [NG: Expression-statement expansion] ************************************ 
skipping: [localhost]

TASK: [OK: ['a', 'b', 'c', 1]] ************************************************ 
ok: [localhost] => {
    "msg": [
        "a", 
        "b", 
        "c", 
        1
    ]
}

TASK: [OK: ['a', 'b', 'c', 1, 2, 3]] ****************************************** 
ok: [localhost] => {
    "msg": [
        "a", 
        "b", 
        "c", 
        1, 
        2, 
        3
    ]
}

TASK: [OK: ['a', 'b', 'c', 1]] ************************************************ 
ok: [localhost] => {
    "msg": [
        1
    ]
}

PLAY RECAP ******************************************************************** 
localhost                  : ok=7    changed=0    unreachable=0    failed=0   

basicexp-playbook.yml

---
- hosts: localhost
  gather_facts: no
  vars:
    strabc: a,b,c
    listabc: [a, b, c]
  tasks:
    - name: "OK: ['a', 'b', 'c']"
      debug:
        msg: |
          {{ strabc.split(',') }}
    - name: "OK: 'a,b,c'"
      debug:
        msg: |
          {{ ','.join(listabc) }}
    - name: "OK: ['a', 'b']"
      debug:
        msg: |
          {{ listabc[0:2] }}
    - name: "OK: a,b,c"
      debug:
        msg: |
          {% set o = strabc %}
          {{ o }}
    - name: "NG: Sequence assignment"
      debug:
        msg: |
          {% set listabc[0] = 1 %}
          {{ listabc }}
      when: false
    - name: "NG: Built-in functions like len(), map()"
      debug:
        msg: |
          {{ len(listabc) }}
      when: false
    - name: "NG: Expression only in {% %} statement"
      debug:
        msg: |
          {% listabc.append(1) %}
          {{ listabc }}
      when: false
    - name: "NG: Expression-statement expansion"
      debug:
        msg: |
          {% do listabc.append(1) %}
          {{ listabc }}
      when: false
    - name: "OK: ['a', 'b', 'c', 1]"
      debug:
        msg: |
          {% if listabc.append(1) %}{% endif %}
          {{ listabc }}
    - name: "OK: ['a', 'b', 'c', 1, 2, 3]"
      debug:
        msg: |
          {% set dummy = listabc.extend([1, 2, 3]) %}
          {{ listabc }}
    - name: "OK: ['a', 'b', 'c', 1]"
      debug:
        msg: |
          {% set o = [1] %}
          {% for i in listabc %}
          {%   set o = o + [ i + ':123' ] %}
          {% endfor %}
          {{ o }}

dictfilter-log.txt

$ ansible-playbook -i localhost, dictfilter-playbook.yml

PLAY [localhost] ************************************************************** 

TASK: [debug ] **************************************************************** 
ok: [localhost] => {
    "var": {
        "dict_filtered": {
            "baz": [
                "D", 
                "E"
            ], 
            "foo": [
                "A", 
                "B", 
                "C"
            ]
        }
    }
}

PLAY RECAP ******************************************************************** 
localhost                  : ok=1    changed=0    unreachable=0    failed=0   

dictfilter-playbook.yml

---
- hosts: localhost
  gather_facts: no
  vars:
    dict: { foo: [A, B, C], bar: [], baz: [D, E] }
    dict_filtered: |
      {% set o = {} %}
      {% for k, v in dict.iteritems() %}
      {%   if v %}
      {%     set _ = o.update({k: v}) %}
      {%   endif %}
      {% endfor %}
      {{ o }}
  tasks:
    - debug:
        var: dict_filtered

distpubkey-hosts.txt

server1
server2
server3
server4

distpubkey-playbook.yml

---
- hosts: all
  become: yes
  become_user: sshuser
  vars:
    all_user_keys: |
      {% set o = [] %}
      {% for i in play_hosts %}
      {%   set _ = o.append(hostvars[i].pubkey) %}
      {% endfor %}
      {{ o }}
    all_host_keys: |
      {% set o = [] %}
      {% for i in play_hosts %}
      {%   set v = hostvars[i] %}
      {%   set h = ','.join([i,v.ansible_fqdn]+v.ansible_all_ipv4_addresses) %}
      {%   set k = ' '.join([h, 'ssh-rsa', v.ansible_ssh_host_key_rsa_public]) %}
      {%   set _ = o.append({'name': i, 'key': k}) %}
      {% endfor %}
      {{ o }}
  tasks:
    - shell: ssh-keygen -q -f ~/.ssh/id_rsa -N ''
      args:
        creates: ~/.ssh/id_rsa
    - shell: cat ~/.ssh/id_rsa.pub
      register: reg
    - set_fact:
        pubkey: "{{reg.stdout}}"
    - authorized_key:
        user: "{{ansible_user_id}}"
        key: "{{item}}"
      with_items: all_user_keys
    - known_hosts:
        name: "{{item.name}}"
        key: "{{item.key}}"
      with_items: all_host_keys

listexp-log.txt

$ ansible-playbook -i localhost, listexp-playbook.yml

PLAY [localhost] ************************************************************** 

TASK: [OK: ['a:A', 'b:B', 'c:C']] ********************************************* 
ok: [localhost] => {
    "msg": [
        "a:A", 
        "b:B", 
        "c:C"
    ]
}

TASK: [OK: ['a:1', 'c:3']] **************************************************** 
ok: [localhost] => {
    "msg": [
        "a:1", 
        "c:3"
    ]
}

TASK: [OK: 6] ***************************************************************** 
ok: [localhost] => {
    "msg": "6"
}

TASK: [NG: 0] ***************************************************************** 
ok: [localhost] => {
    "msg": "0"
}

PLAY RECAP ******************************************************************** 
localhost                  : ok=4    changed=0    unreachable=0    failed=0   

listexp-playbook.yml

---
- hosts: localhost
  gather_facts: no
  vars:
    listabc: [a, b, c]
    dictabc: { a: 1, b: 2, c: 3 }
    list123: [1, 2, 3]
  tasks:
    - name: "OK: ['a:A', 'b:B', 'c:C']"
      debug:
        msg: |
          {% set o = [] %}
          {% for i in listabc %}
          {%   set _ = o.append(i + ':' + i | upper) %}
          {% endfor %}
          {{ o }}
    - name: "OK: ['a:1', 'c:3']"
      debug:
        msg: |
          {% set o = [] %}
          {% for k, v in dictabc | dictsort %}
          {%   if v is odd %}
          {%     set _ = o.append(k + ':' + v | string) %}
          {%   endif %}
          {% endfor %}
          {{ o }}
    - name: "OK: 6"
      debug:
        msg: |
          {% set o = [0] %}
          {% for i in list123 %}
          {%   set _ = o.append(o.pop() + i) %}
          {% endfor %}
          {{ o[0] }}
    - name: "NG: 0"
      debug:
        msg: |
          {% set o = 0 %}
          {% for i in list123 %}
          {%   set o = o + i %}
          {% endfor %}
          {{ o }}

listjoin-hosts.txt

master1         ansible_ssh_host=10.0.45.11
master2         ansible_ssh_host=10.0.45.12
master3         ansible_ssh_host=10.0.45.13
slave1          ansible_ssh_host=10.0.45.51
slave2          ansible_ssh_host=10.0.45.52
slave3          ansible_ssh_host=10.0.45.53

[master_servers]
master1
master2
master3

listjoin-log.txt

$ ansible-playbook -i listjoin-hosts.txt listjoin-playbook.yml

PLAY [localhost] ************************************************************** 

TASK: [debug ] **************************************************************** 
ok: [localhost] => {
    "var": {
        "zkurl": "zk://10.0.45.11:2181,10.0.45.12:2181,10.0.45.13:2181/mesos"
    }
}

PLAY RECAP ******************************************************************** 
localhost                  : ok=1    changed=0    unreachable=0    failed=0   

listjoin-playbook.yml

---
- hosts: localhost
  gather_facts: no
  vars:
    zkurl: |
      {% set o = [] %}
      {% for i in groups.master_servers %}
      {%   set _ = o.append(hostvars[i].ansible_ssh_host+':2181') %}
      {% endfor %}
      zk://{{ o | join(',') }}/mesos
  tasks:
    - debug:
        var: zkurl

run.sh

#!/bin/bash

run() {
        echo "$ $*"
        "$@"
}

run ansible-playbook -i localhost, basicexp-playbook.yml > basicexp-log.txt
run ansible-playbook -i localhost, listexp-playbook.yml > listexp-log.txt
run ansible-playbook -i listjoin-hosts.txt listjoin-playbook.yml > listjoin-log.txt
run ansible-playbook -i localhost, dictfilter-playbook.yml > dictfilter-log.txt
run ansible-playbook -i setjoin-hosts.txt setjoin-playbook.yml > setjoin-log.txt
#run ansible-playbook -i distpubkey-hosts.txt distpubkey-playbook.yml > distpubkey-log.txt

setjoin-hosts.txt

[tag_Name_Zookeeper_1]
a
b
[tag_Name_Zookeeper_2]
a
c
[tag_Name_Zookeeper_3]
b
d
[others]
localhost

setjoin-log.txt

$ ansible-playbook -i setjoin-hosts.txt setjoin-playbook.yml

PLAY [localhost] ************************************************************** 

TASK: [debug ] **************************************************************** 
ok: [localhost] => {
    "var": {
        "Node": "a:2181,b:2181,c:2181,d:2181"
    }
}

PLAY RECAP ******************************************************************** 
localhost                  : ok=1    changed=0    unreachable=0    failed=0   

setjoin-playbook.yml

---
- hosts: localhost
  gather_facts: no
  vars:
    Node: |
      {% set o = {} %}
      {% for g, h in groups.iteritems() %}
      {%   if g.startswith('tag_Name_Zookeeper') %}
      {%     for i in h %}
      {%       set _ = o.update({i+':2181': 1}) %}
      {%     endfor %}
      {%   endif %}
      {% endfor %}
      {{ o.keys() | sort | join(',') }}
  tasks:
    - debug:
        var: Node