如果某些文件发生更改，我如何运行ansible命令

Question

我正在使用ansible部署我的django App

使用

- name: Upgrade the virtualenv.
  pip: requirements={{project_root}}/www/requirements.txt virtualenv={{project_root}}/www/virtualenv

但我只想在上次运行后requirements.txt发生变化的情况下运行它

Answer 1

我们需要确定是否有任何需求文件已更改。具体步骤如下：

1. 触摸临时要求文件。(如果它们不存在，新的空白file)
2. Calculate的md5将不同先前需求的md5散列和当前需求文件(刚从GIT中拉下的那些)的md5散列)
3. 在步骤中迭代这些md5命令的结果，比较pip散列，注册tmp的输出如果#4中的任何结果发生更改，我们将pip packages
4. Copy当前需求文件安装到临时位置。

这是我的行动手册，{{virtualenv.requirements}}是需求文件的列表，例如：['/work/project/requirements.txt', '/work/project/requirements-prod.txt']

- name: Assures temp requirements directory exists
  file: path="/tmp{{ virtualenv.path }}" state=directory
  sudo: yes
  when: install_pip_packages

- name: Assures temp requirements files exists
  file: path="/tmp{{ item }}" state=touch
  sudo: yes
  with_items: virtualenv.requirements_files
  when: install_pip_packages

- name: Calculate md5 of temp requirements
  stat: path="/tmp{{ item }}"
  with_items: virtualenv.requirements_files
  register: temp_requirements_stat
  when: install_pip_packages

- name: Calculate md5 of current requirements
  stat: path="{{ item }}"
  with_items: virtualenv.requirements_files
  register: current_requirements_stat
  when: install_pip_packages

- name: Check requirement files for changes
  command: test {{ temp_requirements_stat.results[item.0].stat.md5 }} = {{ current_requirements_stat.results[item.0].stat.md5 }}
  changed_when: "requirements_check.rc != 0"
  failed_when: requirements_check.stderr
  with_indexed_items: virtualenv.requirements_files
  register: requirements_check
  when: install_pip_packages

- name: Install packages required by the Django app inside virtualenv
  pip: virtualenv={{ virtualenv.path }} extra_args='-U' requirements="{{ virtualenv.requirements_files | join(' -r ') }}"
  when: install_pip_packages and requirements_check.changed

- name: Copy requirements to /tmp
  command: cp "{{ item }}" "/tmp{{ item }}"
  sudo: yes
  with_items: virtualenv.requirements_files
  when: install_pip_packages

Answer 2

这里有两个选项：

notify

• 将你的模板置于Ansible控制之下，使用‘requirements.txt’或'template‘模块，然后用'notify:’调用'pip‘模块，方法更复杂：

- retrieve md5 sum of requirements.txt on each Ansible run and compare it with saved md5 somewhere on the server ('stat' module could be used)
- retrieve pre-saved md5 sum of requirements.txt
- if current md5 is not equal to presaved, then invoke pip task ('when:' statement)
- save new md5 somewhere on the server for next Ansible run

​

Answer 3

我在git仓库中使用了这个相当简短的变通方法。

  - name: get requirements changes since last pull
    shell: "cd {{ project_root }}; git log --name-status --oneline origin/master
           {{ git_result.before }}..{{ git_result.after }} | grep requirements.txt"
    register: pip_check
    failed_when: false

  - name: update pip requirements
    pip: requirements={{ project_root }}/requirements.txt
         virtualenv=~/.virtualenvs/www/
    when: pip_check.stdout_lines

它不是通用的，也不是跨平台的配方，但在许多情况下都能很好地工作。