community.general/plugins/modules/consul_kv.py

#!/usr/bin/python
# -*- coding: utf-8 -*-
#
# Copyright (c) 2015, Steve Gargan <steve.gargan@gmail.com>
# Copyright (c) 2018 Genome Research Ltd.
# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
# SPDX-License-Identifier: GPL-3.0-or-later

from __future__ import absolute_import, division, print_function
__metaclass__ = type


DOCUMENTATION = r"""
module: consul_kv
short_description: Manipulate entries in the key/value store of a Consul cluster
description:
  - Allows the retrieval, addition, modification and deletion of key/value entries in a Consul cluster using the agent. The
    entire contents of the record, including the indices, flags and session are returned as C(value).
  - If the O(key) represents a prefix then note that when a value is removed, the existing value if any is returned as part
    of the results.
  - See http://www.consul.io/docs/agent/http.html#kv for more details.
requirements:
  - py-consul
  - requests
author:
  - Steve Gargan (@sgargan)
  - Colin Nolan (@colin-nolan)
extends_documentation_fragment:
  - community.general.attributes
attributes:
  check_mode:
    support: full
  diff_mode:
    support: none
options:
  state:
    description:
      - The action to take with the supplied key and value. If the state is V(present) and O(value) is set, the key contents
        is set to the value supplied and C(changed) is set to V(true) only if the value was different to the current contents.
        If the state is V(present) and O(value) is not set, the existing value associated to the key is returned. The state
        V(absent) is used to remove the key/value pair, again C(changed) is set to V(true) only if the key actually existed
        prior to the removal. An attempt can be made to obtain or free the lock associated with a key/value pair with the
        states V(acquire) or V(release) respectively. A valid session must be supplied to make the attempt C(changed) is V(true)
        if the attempt is successful, V(false) otherwise.
    type: str
    choices: [absent, acquire, present, release]
    default: present
  key:
    description:
      - The key at which the value should be stored.
    type: str
    required: true
  value:
    description:
      - The value should be associated with the given key, required if O(state) is V(present).
    type: str
  recurse:
    description:
      - If the key represents a prefix, each entry with the prefix can be retrieved by setting this to V(true).
    type: bool
  retrieve:
    description:
      - If the O(state) is V(present) and O(value) is set, perform a read after setting the value and return this value.
    default: true
    type: bool
  session:
    description:
      - The session that should be used to acquire or release a lock associated with a key/value pair.
    type: str
  token:
    description:
      - The token key identifying an ACL rule set that controls access to the key value pair.
    type: str
  cas:
    description:
      - Used when acquiring a lock with a session. If the O(cas) is V(0), then Consul only puts the key if it does not already
        exist. If the O(cas) value is non-zero, then the key is only set if the index matches the ModifyIndex of that key.
    type: str
  flags:
    description:
      - Opaque positive integer value that can be passed when setting a value.
    type: str
  host:
    description:
      - Host of the Consul agent.
    type: str
    default: localhost
  port:
    description:
      - The port on which the Consul agent is running.
    type: int
    default: 8500
  scheme:
    description:
      - The protocol scheme on which the Consul agent is running.
    type: str
    default: http
  validate_certs:
    description:
      - Whether to verify the tls certificate of the Consul agent.
    type: bool
    default: true
  datacenter:
    description:
      - The name of the datacenter to query. If unspecified, the query defaults to the datacenter of the Consul agent on O(host).
    type: str
    version_added: 10.0.0
"""


EXAMPLES = r"""
# If the key does not exist, the value associated to the "data" property in `retrieved_key` will be `None`
# If the key value is empty string, `retrieved_key["data"]["Value"]` will be `None`
- name: Retrieve a value from the key/value store
  community.general.consul_kv:
    key: somekey
  register: retrieved_key

- name: Add or update the value associated with a key in the key/value store
  community.general.consul_kv:
    key: somekey
    value: somevalue

- name: Remove a key from the store
  community.general.consul_kv:
    key: somekey
    state: absent

- name: Add a node to an arbitrary group using Consul inventory (see consul.ini)
  community.general.consul_kv:
    key: ansible/groups/dc1/somenode
    value: top_secret

- name: Register a key/value pair with an associated session
  community.general.consul_kv:
    key: stg/node/server_birthday
    value: 20160509
    session: "{{ sessionid }}"
    state: acquire
"""

from ansible.module_utils.common.text.converters import to_text

try:
    import consul
    from requests.exceptions import ConnectionError
    python_consul_installed = True
except ImportError:
    python_consul_installed = False

from ansible.module_utils.basic import AnsibleModule

# Note: although the py-consul implementation implies that using a key with a value of `None` with `put` has a special
# meaning (https://github.com/criteo/py-consul/blob/master/consul/api/kv.py), if not set in the subsequently API call,
# the value just defaults to an empty string (https://www.consul.io/api/kv.html#create-update-key)
NOT_SET = None


def _has_value_changed(consul_client, key, target_value):
    """
    Uses the given Consul client to determine if the value associated to the given key is different to the given target
    value.
    :param consul_client: Consul connected client
    :param key: key in Consul
    :param target_value: value to be associated to the key
    :return: tuple where the first element is the value of the "X-Consul-Index" header and the second is `True` if the
    value has changed (i.e. the stored value is not the target value)
    """
    index, existing = consul_client.kv.get(key)
    if not existing:
        return index, True
    try:
        changed = to_text(existing['Value'], errors='surrogate_or_strict') != target_value
        return index, changed
    except UnicodeError:
        # Existing value was not decodable but all values we set are valid utf-8
        return index, True


def execute(module):
    state = module.params.get('state')

    if state == 'acquire' or state == 'release':
        lock(module, state)
    elif state == 'present':
        if module.params.get('value') is NOT_SET:
            get_value(module)
        else:
            set_value(module)
    elif state == 'absent':
        remove_value(module)
    else:
        module.exit_json(msg="Unsupported state: %s" % (state, ))


def lock(module, state):

    consul_api = get_consul_api(module)

    session = module.params.get('session')
    key = module.params.get('key')
    value = module.params.get('value')

    if not session:
        module.fail(
            msg='%s of lock for %s requested but no session supplied' %
            (state, key))

    index, changed = _has_value_changed(consul_api, key, value)

    if changed and not module.check_mode:
        if state == 'acquire':
            changed = consul_api.kv.put(key, value,
                                        cas=module.params.get('cas'),
                                        acquire=session,
                                        flags=module.params.get('flags'))
        else:
            changed = consul_api.kv.put(key, value,
                                        cas=module.params.get('cas'),
                                        release=session,
                                        flags=module.params.get('flags'))

    module.exit_json(changed=changed,
                     index=index,
                     key=key)


def get_value(module):
    consul_api = get_consul_api(module)
    key = module.params.get('key')

    index, existing_value = consul_api.kv.get(key, recurse=module.params.get('recurse'))

    module.exit_json(changed=False, index=index, data=existing_value)


def set_value(module):
    consul_api = get_consul_api(module)

    key = module.params.get('key')
    value = module.params.get('value')

    if value is NOT_SET:
        raise AssertionError('Cannot set value of "%s" to `NOT_SET`' % key)

    index, changed = _has_value_changed(consul_api, key, value)

    if changed and not module.check_mode:
        changed = consul_api.kv.put(key, value,
                                    cas=module.params.get('cas'),
                                    flags=module.params.get('flags'))

    stored = None
    if module.params.get('retrieve'):
        index, stored = consul_api.kv.get(key)

    module.exit_json(changed=changed,
                     index=index,
                     key=key,
                     data=stored)


def remove_value(module):
    ''' remove the value associated with the given key. if the recurse parameter
     is set then any key prefixed with the given key will be removed. '''
    consul_api = get_consul_api(module)

    key = module.params.get('key')

    index, existing = consul_api.kv.get(
        key, recurse=module.params.get('recurse'))

    changed = existing is not None
    if changed and not module.check_mode:
        consul_api.kv.delete(key, module.params.get('recurse'))

    module.exit_json(changed=changed,
                     index=index,
                     key=key,
                     data=existing)


def get_consul_api(module):
    return consul.Consul(host=module.params.get('host'),
                         port=module.params.get('port'),
                         scheme=module.params.get('scheme'),
                         verify=module.params.get('validate_certs'),
                         token=module.params.get('token'),
                         dc=module.params.get('datacenter'))


def test_dependencies(module):
    if not python_consul_installed:
        module.fail_json(msg="python-consul required for this module. "
                             "see https://python-consul.readthedocs.io/en/latest/#installation")


def main():

    module = AnsibleModule(
        argument_spec=dict(
            cas=dict(type='str'),
            datacenter=dict(type='str'),
            flags=dict(type='str'),
            key=dict(type='str', required=True, no_log=False),
            host=dict(type='str', default='localhost'),
            scheme=dict(type='str', default='http'),
            validate_certs=dict(type='bool', default=True),
            port=dict(type='int', default=8500),
            recurse=dict(type='bool'),
            retrieve=dict(type='bool', default=True),
            state=dict(type='str', default='present', choices=['absent', 'acquire', 'present', 'release']),
            token=dict(type='str', no_log=True),
            value=dict(type='str', default=NOT_SET),
            session=dict(type='str'),
        ),
        supports_check_mode=True
    )

    test_dependencies(module)

    try:
        execute(module)
    except ConnectionError as e:
        module.fail_json(msg='Could not connect to consul agent at %s:%s, error was %s' % (
            module.params.get('host'), module.params.get('port'), e))
    except Exception as e:
        module.fail_json(msg=str(e))


if __name__ == '__main__':
    main()