获得第一个“N"Ansible 中 Jinja2 模板中列表的元素 [英] Get first "N" elements of a list in Jinja2 template in Ansible
问题描述
我的大多数位置都有 4 个以上的 DNS 源,但有一些位置较少.每个位置都有自己的 dns4_ips
列表变量,如下所示:
Most of my locations have 4+ DNS sources, but a few have less. Each location gets their own dns4_ips
list variable like this:
dns4_ips:
- dns_A
- dns_B
- dns_C
- dns_C
我的 resolv.conf 模板如下所示:
My resolv.conf template looks like this:
domain example.com
search example.com dom2.example.com dom3.example.com
{% for nameserver in (dns4_ips|shuffle(seed=inventory_hostname)) %}
nameserver {{nameserver}}
{% endfor %}
Jinja for
循环效果很好,但在我有很多名称服务器的情况下,我宁愿只列出 shuffle()
返回的前 3 个.
The Jinja for
loop works great, but in the cases where I have numerous nameservers I'd rather only list the first 3 that the shuffle()
returns.
我想到了这个:
nameserver {{ (dns4_ips|shuffle(seed=inventory_hostname))[0] }}
nameserver {{ (dns4_ips|shuffle(seed=inventory_hostname))[1] }}
nameserver {{ (dns4_ips|shuffle(seed=inventory_hostname))[2] }}
...但在某些情况下,我只有一个或两个可用的 DNS 服务器,因此它们会产生不正确的行或错误,对吗?
...but there are some cases where I only have one or two DNS servers available so those would produce either an incorrect line or an error, correct?
是否有一种干净的方法可以使用 for 循环来处理这个问题,或者我是否需要将三个名称服务器行包装在 {% if (dns4_ips|shuffle(seed=inventory_hostname))[1] is defined %}
?
Is there a clean way to handle this with the for loop, or do I need to wrap the three nameserver lines in {% if (dns4_ips|shuffle(seed=inventory_hostname))[1] is defined %}
?
推荐答案
简单:
domain example.com
search example.com dom2.example.com dom3.example.com
{% for nameserver in (dns4_ips|shuffle(seed=inventory_hostname))[:3] %}
nameserver {{nameserver}}
{% endfor %}
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