每个数据库名称一次Ansible运行任务 [英] Ansible run task once per database-name

问题描述

我正在使用ansible将多个站点部署到同一台服务器上.每个站点都是hosts库存中单独的主机"，效果很好.

I'm using ansible to deploy several sites to the same server. Each site is a separate 'host' in the ansible hosts inventory, which works really well.

但是，只有两个数据库:生产和测试. 如何确保我的数据库迁移任务每个数据库仅运行一次?

However, there are only two databases: production and testing. How can I make sure my database-migration task only runs once per database?

我已经阅读了group_by，run_once和delegate_to功能，但是我不确定如何将它们组合在一起.

I've read into the group_by, run_once and delegate_to features, but I'm not sure how to combine those.

主机看起来像:

[production]
site1.example.com       ansible_ssh_host=webserver.example.com
site2.example.com       ansible_ssh_host=webserver.example.com

[beta]
beta-site1.example.com  ansible_ssh_host=webserver.example.com
beta-site2.example.com  ansible_ssh_host=webserver.example.com

[all:children]
production
beta

当前的剧本看起来像这样:

The current playbook looks like this:

---
- hosts: all
- tasks:

  # ...

  - name: "postgres:  Create PostgreSQL database"
    sudo: yes
    sudo_user: postgres
    postgresql_db: db="{{ DATABASES.default.NAME }}" state=present template=template0 encoding='UTF-8' lc_collate='en_US.UTF-8' lc_ctype='en_US.UTF-8'
    tags: postgres
    register: createdb
    delegate_to: "{{ DATABASES.default.HOST|default(inventory_hostname) }}"

  # ...

  - name: "django-post:  Create Django database tables (migrate)"
    django_manage: command=migrate app_path={{ src_dir }} settings={{ item.settings }} virtualenv={{ venv_dir }}
    with_items: django_projects
    #run_once: true
    tags:
    - django-post
    - django-db
    - migrate

推荐答案

我发现的最好方法是将任务的执行限制在组的第一台主机上.因此，您需要将组名和数据库添加到group_vars文件中，例如:

The best way I found was to restrict the execution of a task to the first host of a group. Therefore you need to add the groupname and the databases to a group_vars file like:

group_vars/production

group_vars/production

---
dbtype=production
django_projects:
    - name: project_1
      settings: ...
    - name: project_n
      settings: ...

group_vars/beta

group_vars/beta

---
dbtype=beta
django_projects:
    - name: project_1
      settings: ...
    - name: project_n
      settings: ...

主机

hosts

[production]
site1.example.com       ansible_ssh_host=localhost ansible_connection=local
site2.example.com       ansible_ssh_host=localhost ansible_connection=local

[beta]
beta-site1.example.com  ansible_ssh_host=localhost ansible_connection=local
beta-site2.example.com  ansible_ssh_host=localhost ansible_connection=local


[all:children]
production
beta

并将任务执行限制为与该组匹配的第一台主机:

and limit the task execution to the first host that matches that group:

- name: "django-post:  Create Django database tables (migrate)"
  django_manage: command=migrate app_path={{ src_dir }} settings={{ item.settings }} virtualenv={{ venv_dir }}
  with_items: django_projects
  when: groups[dbtype][0] == inventory_hostname 
  tags:
    - django-post
    - django-db
    - migrate

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