Ansible 中的幂等性和随机变量 [英] Idempotence and Random Variables in Ansible
问题描述
有没有办法保证使用随机生成变量的剧本的幂等性?
Is there a way to guarantee idempotence for playbooks that use randomly generated variables?
例如,我想设置我的 crontabs 以在不同时间触发多台服务器上的电子邮件,所以我使用 ansible 的 set_fact 模块创建随机整数:
For example, I want to setup my crontabs to trigger emails on multiple servers at different times, so I create random integers using ansible's set_fact module:
tasks:
- set_fact:
first_run_30="{{ 30 | random }}"
run_once: yes
然后使用 ansible 将这些生成的变量应用到我的 crontab 中,如下所示:
Then apply those generated variables to my crontab using ansible like so:
- name: Setup cron30job
cron: name=cron30job minute={{first_run_30}},{{first_run_30 | int + 30}} job='/bin/bash /cron30job.sh' state=present user=root
environment:
MAILTO: 'me@somelist.com'
MAILFROM: 'me@somehost.com'
这很有效,但是,我相信使用这种策略会破坏 ansible 的幂等原则,因为每次播放时您都会看到变化:
This works very well, however, ansible's indempotence principle is, I believe, broken using this strategy because each time a play is made you see a change:
TASK: [Setup cron30job] *****************************************
changed: [127.0.0.1]
此外,在三个独立运行期间,每次都在 root 下检查 crontab:
Further, in the crontab checking under root each time during three separate runs:
[ansible]# cat /var/spool/cron/root
#Ansible: cron30job
5,35 * * * * /bin/bash /sw/test/cron30job.sh
#Ansible: cron30job
9,39 * * * * /bin/bash /sw/test/cron30job.sh
#Ansible: cron30job
6,36 * * * * /bin/bash /sw/test/cron30job.sh
如果有解决方法,或者在我的方案中可能无法实现无幂等,我想知道.
If there is a workaround, or maybe indempotence just will not be possible in my scenario, I would like to know.
推荐答案
您可以获得与节点相关的信息,例如主机名的哈希值或 IP 地址的最后一个字节,而不是随机值.
Instead of a random value, you could get something related to the node, like an hash of the hostname or the last byte of the ip address.
这是一个例子:
- name: Get a pseudo-random minute
shell: expr $((16#`echo "{{inventory_hostname}}" | md5sum | cut -c 1-4`)) % 30
register: minute
changed_when: false
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