linearregression / ansible-lint

Best practices checker for Ansible

Ansible-lint

ansible-lint checks playbooks for practices and behaviour that could potentially be improved

Setup

Using pip:

pip install ansible-lint

From source:

git clone https://github.com/willthames/ansible-lint
export PYTHONPATH=$PYTHONPATH:`pwd`/ansible-lint/lib
export PATH=$PATH:`pwd`/ansible-lint/bin

Usage

Usage: ansible-lint playbook.yml|roledirectory ...

Options:
  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -L                    list all the rules
  -q                    quieter, although not silent output
  -p                    parseable output in the format of pep8
  -r RULESDIR           specify one or more rules directories using one or
                        more -r arguments. Any -r flags override the default
                        rules in ['/path/to/ansible-
                        lint/lib/ansiblelint/rules'], unless -R is also used.
  -R                    Use default rules ['/path/to/ansible-
                        lint/lib/ansiblelint/rules'] in addition to any extra
                        rules directories specified with -r. There is no need
                        to specify this if no -r flags are used
  -t TAGS               only check rules whose id/tags match these values
  -T                    list all the tags
  -x SKIP_LIST          only check rules whose id/tags do not match these
                        values
  --exclude=EXCLUDE_PATHS
                        path to directories or files to skip. This option is
                        repeatable.

False positives

Some rules are a bit of a rule of thumb. Advanced git, yum or apt usage, for example, is typically difficult to achieve through the modules. In this case, you should mark the task so that warnings aren't produced.

There are two mechanisms for this - one works with all tasks, the other works with the command checking modules.

Use the warn parameter with the command or shell module.

Use skip_ansible_lint tag with any task that you want to skip.

I recommend commenting the reasons why you're skipping the check. Unfortunately ansible-lint is unable to check for such comments at this time! (patches welcome)

- name: this would typically fire CommandsInsteadOfArgumentRule
  command: warn=no chmod 644 X

- name: this would typically fire CommandsInsteadOfModuleRule
  command: git pull --rebase
  args:
    warn: False

- name: this would typically fire GitHasVersionRule
  git: src=/path/to/git/repo dest=checkout 
  tags:
  - skip_ansible_lint

Rules

Rules are described using a class file per rule. Default rules are named DeprecatedVariableRule.py, etc.

Each rule definition should have the following:

• ID: A unique identifier
• Short description: Brief description of the rule
• Description: Behaviour the rule is looking for
• Tags: one or more tags that may be used to include or exclude the rule
• At least one of the following methods:
  • match that takes a line and returns None or False if the line doesn't match the test and True or a custom message (this allows one rule to test multiple behaviours - see e.g. the CommandsInsteadOfModulesRule
  • matchblock that takes the details about the file and a block. It returns None or False if the line doesn't match the test and True or a custom message.
  • matchtask operates on a single task or handler. Such a task get standardized to always contain a module key and module_arguments key. Other common task modifiers such as when, with_items etc. are also available as keys if present in the task.

An example rule using match is:

from ansiblelint import AnsibleLintRule

class DeprecatedVariableRule(AnsibleLintRule):

    id = 'ANSIBLE0001'
    shortdesc = 'Deprecated variable declarations'
    description = 'Check for lines that have old style ${var} ' + \
                  'declarations'
    tags = { 'deprecated' }


    def match(self, file, line):
        return '${' in line

An example rule using matchtask is:

import ansiblelint.utils
from ansiblelint import AnsibleLintRule

class TaskHasTag(AnsibleLintRule):
    id = 'ANSIBLE0008'
    shortdesc = 'Tasks must have tag'
    description = 'Tasks must have tag'
    tags = ['productivity']


    def matchtask(self, file, task):
        # If the task include another task or make the playbook fail
        # Don't force to have a tag
        if not set(task.keys()).isdisjoint(['include','fail']):
            return False

        # Task should have tags
        if not task.has_key('tags'):
              return True

        return False

The task argument to matchtask contains a number of keys - the critical one is action. The value of task['action'] contains the module being used, and the arguments passed, both as key-value pairs and a list of other arguments (e.g. the command used with shell)

In ansible-lint 2.0.0, task['action']['args'] was renamed task['action']['module_arguments'] to avoid a clash when a module actually takes args as a parameter key (e.g. ec2_tag) Examples

There are some example playbooks with undesirable features. Running ansible-lint on them works:

$ ansible-lint examples/example.yml
[ANSIBLE0004] Git checkouts must contain explicit version
examples/example.yml:15
Task/Handler: git check

[ANSIBLE0004] Git checkouts must contain explicit version
examples/example.yml:18
Task/Handler: git check 2

[ANSIBLE0004] Git checkouts must contain explicit version
examples/example.yml:30
Task/Handler: using git module

[ANSIBLE0002] Trailing whitespace
examples/example.yml:13
    action: do nothing   

[ANSIBLE0002] Trailing whitespace
examples/example.yml:35
    with_items: 

[ANSIBLE0006] git used in place of git module
examples/example.yml:24
Task/Handler: executing git through command

[ANSIBLE0006] git used in place of git module
examples/example.yml:27
Task/Handler: executing git through command

[ANSIBLE0006] git used in place of git module
examples/example.yml:30
Task/Handler: executing git through command

If playbooks include other playbooks, or tasks, or handlers or roles, these are also handled:

$ bin/ansible-lint examples/include.yml
[ANSIBLE0004] Checkouts must contain explicit version
/Users/will/src/ansible-lint/examples/roles/bobbins/tasks/main.yml:3
action: git a=b c=d

As of version 2.4.0, ansible-lint now works just on roles (this is useful for CI of roles)

Contributing

Please read CONTRIBUTING.md if you wish to contribute.