General
- YAML files - All yaml files should use 2 space indents and end with
.yml
- Variables - Use jinja variable syntax over deprecated variable syntax.
{{ var }}
not$var
- Use spaces around jinja variable names.
{{ var }}
not{{var}}
- Variables that are environment specific and that need to be overridden should be in ALL CAPS.
- Variables that are internal to the role should be lowercase.
- Prefix all variables defined in a role with the name of the role. Example:
EDXAPP_FOO
- Keep roles self contained - Roles should avoid including tasks from other roles when possible
- Plays should do nothing more than include a list of roles except where pre_tasks and post_tasks are required (to manage a load balancer for example)
- Plays/Playbooks that apply to the general community should be copied to configuration/playbooks
- Plays/Playbooks that apply only to a specific organization (edx-east, edx-west) should be copied to a sub-directory under configuration/playbooks
- Handlers - Do not use handlers. If you need to restart an app when specific tasks run, just add a task to do so at the end of the playbook. If necessary, it can be skipped with tags (see Role Life-cycle)
- Separators - Use underscores (e.g.
my_role
) not dashes (my-role
). - Paths - When defining paths, do not include trailing slashes (e.g.
my_path: /foo
notmy_path: /foo/
. When concatenating paths, follow the same convention (e.g.{{ my_path }}/bar
not{{ my_path }}bar
) - Tag tasks using the tags described in Role Life-cycle
Conditionals and Return Status
- Always use
when:
for conditionals - To check if a variable is definedwhen: my_var is defined
orwhen: my_var is not defined
To verify return status (see conditionals)
- command: /bin/false register: my_result ignore_errors: True - debug: msg="task failed" when: my_result|failed
Formatting
Use yaml-style blocks.
Good:- file: dest: "{{ test }}" src: "./foo.txt" mode: 0770 state: present user: "root" group: "wheel"
Bad:
- file: > dest={{ test }} src=./foo.txt mode=0770 state=present user=root group=wheel
Break long lines using yaml line continuation.
Reference: http://docs.ansible.com/playbooks_intro.html- shell: > python a very long command --with=very --long-options=foo --and-even=more_options --like-these
Roles
Role Variables
- "common" role - Contains tasks that apply to all roles that are edX specific.
- "common_vars" role - Contains vars that apply to all roles that are edX specific.
- Roles variables - Variables specific to a role should be defined in /vars/main.yml. All variables should be prefixed with the role name.
- Role defaults - Default variables should configure a role to install edx in such away that all services can run on a single server
- Variables that are environment specific and that need to be overridden should be in all caps.
Every role should have a standard set of role directories, example that includes a python and ruby virtualenv:
edxapp_data_dir: "{{ COMMON_DATA_DIR }}/edxapp" edxapp_app_dir: "{{ COMMON_APP_DIR }}/edxapp" edxapp_log_dir: "{{ COMMON_LOG_DIR }}/edxapp" edxapp_venvs_dir: "{{ edxapp_app_dir }}/venvs" edxapp_venv_dir: "{{ edxapp_venvs_dir }}/edxapp" edxapp_venv_bin: "{{ edxapp_venv_dir }}/bin" edxapp_rbenv_dir: "{{ edxapp_app_dir }}" edxapp_rbenv_root: "{{ edxapp_rbenv_dir }}/.rbenv" edxapp_rbenv_shims: "{{ edxapp_rbenv_root }}/shims" edxapp_rbenv_bin: "{{ edxapp_rbenv_root }}/bin" edxapp_gem_root: "{{ edxapp_rbenv_dir }}/.gem" edxapp_gem_bin: "{{ edxapp_gem_root }}/bin"
Role Naming Conventions
- Role names - Terse, one word if possible, use underscores if necessary.
- Role task names - Terse, descriptive, spaces are OK and should be prefixed with the role name.
Secure vs. Insecure data
As a general policy we want to protect the following data:
- Usernames
- Public keys (keys are OK to be public, but can be used to figure out usernames)
- Hostnames
- Passwords, API keys
Directory structure for the secure repository:
ansible
├── files
├── keys
└── vars
The default secure_dir
is set in group_vars/all
and can be overridden by adding another file in group_vars that corresponds to a deploy group name.
For templates or files that are secure use first_available_file
, example:
- name: xserver | install read-only ssh key for the content repo that is required for grading copy: src: "{{ item }}" dest: /etc/git-identity force: yes owner: ubuntu group: adm mode: "0640" first_available_file: - "{{ secure_dir }}/files/git-identity" - "git-identity-example"