ansible-playbook 之 lookup 插件的使用

ansible-playbook 之 lookup 插件的使用

官方资料：链接

一、Using lookup plugins

Lookup plugins can be used anywhere you can use templating in Ansible: in a play, in variables file, or in a Jinja2 template for the template module.

下面为 lookup.yml 的内容

---
- hosts: localhost
  gather_facts: true
  vars:
    host_name: 55.qiweioa.cn
    file_contents: "{{lookup('file', 'file.txt')}}"
  tasks:
  - name: the contents of file.txt
    debug:
      msg: "{{file_contents}}"

[root@VM_129_89_centos playbook]# tree -L 1
.
|-- file.txt
|-- hosts
|-- lookup.yml
`-- playbook.yml

上面为目录结构，运行后可获得 file.txt 里的内容。

Lookups are an integral part of loops. Wherever you see with_, the part after the underscore is the name of a lookup. This is also the reason most lookups output lists and take lists as input; for example, with_items uses the items lookup:

tasks:
  - name: count to 3
    debug: msg={{item}}
    with_items: [1, 2, 3]

You can combine lookups with Filters, Tests and even each other to do some complex data generation and manipulation. For example:

tasks:
  - name: valid but useless and over complicated chained lookups and filters
    debug: msg="find the answer here:\n{{ lookup('url', 'https://google.com/search/?q=' + item|urlencode)|join(' ') }}"
    with_nested:
      - "{{lookup('consul_kv', 'bcs/' + lookup('file', '/the/question') + ', host=localhost, port=2000')|shuffle}}"
      - "{{lookup('sequence', 'end=42 start=2 step=2')|map('log', 4)|list)}}"
      - ['a', 'c', 'd', 'c']

二、Invoking lookup plugins with query

New in version 2.5.

In Ansible 2.5, a new jinja2 function called query was added for invoking lookup plugins. The difference between lookup and query is largely that query will always return a list. The default behavior of lookup is to return a string of comma separated values. lookup can be explicitly configured to return a list using wantlist=True.

This was done primarily to provide an easier and more consistent interface for interacting with the new loop keyword, while maintaining backwards compatibility with other uses of lookup.

The following examples are equivalent:

lookup('dict', dict_variable, wantlist=True)

query('dict', dict_variable)

As demonstrated above the behavior of wantlist=True is implicit when using query.

Additionally, q was introduced as a shortform of query:

q('dict', dict_variable)

三、Plugin list

You can use ansible-doc -t lookup -l to see the list of available plugins. Use ansible-doc -t lookup <plugin name> to see specific documents and examples.