salt/beacons/avahi_announce.py
# -*- coding: utf-8 -*-
'''
Beacon to announce via avahi (zeroconf)
.. versionadded:: 2016.11.0
Dependencies
============
- python-avahi
- dbus-python
'''
# Import Python libs
from __future__ import absolute_import, unicode_literals
import logging
import time
import salt.utils.stringutils
from salt.ext.six.moves import map
# Import 3rd Party libs
try:
import avahi
HAS_PYAVAHI = True
except ImportError:
HAS_PYAVAHI = False
try:
import dbus
from dbus import DBusException
BUS = dbus.SystemBus()
SERVER = dbus.Interface(BUS.get_object(avahi.DBUS_NAME, avahi.DBUS_PATH_SERVER),
avahi.DBUS_INTERFACE_SERVER)
GROUP = dbus.Interface(BUS.get_object(avahi.DBUS_NAME, SERVER.EntryGroupNew()),
avahi.DBUS_INTERFACE_ENTRY_GROUP)
HAS_DBUS = True
except (ImportError, NameError):
HAS_DBUS = False
except DBusException:
HAS_DBUS = False
log = logging.getLogger(__name__)
__virtualname__ = 'avahi_announce'
LAST_GRAINS = {}
def __virtual__():
if HAS_PYAVAHI:
if HAS_DBUS:
return __virtualname__
return False, 'The {0} beacon cannot be loaded. The ' \
'\'python-dbus\' dependency is missing.'.format(__virtualname__)
return False, 'The {0} beacon cannot be loaded. The ' \
'\'python-avahi\' dependency is missing.'.format(__virtualname__)
def validate(config):
'''
Validate the beacon configuration
'''
_config = {}
list(map(_config.update, config))
if not isinstance(config, list):
return False, ('Configuration for avahi_announce '
'beacon must be a list.')
elif not all(x in _config for x in ('servicetype',
'port',
'txt')):
return False, ('Configuration for avahi_announce beacon '
'must contain servicetype, port and txt items.')
return True, 'Valid beacon configuration.'
def _enforce_txt_record_maxlen(key, value):
'''
Enforces the TXT record maximum length of 255 characters.
TXT record length includes key, value, and '='.
:param str key: Key of the TXT record
:param str value: Value of the TXT record
:rtype: str
:return: The value of the TXT record. It may be truncated if it exceeds
the maximum permitted length. In case of truncation, '...' is
appended to indicate that the entire value is not present.
'''
# Add 1 for '=' seperator between key and value
if len(key) + len(value) + 1 > 255:
# 255 - 3 ('...') - 1 ('=') = 251
return value[:251 - len(key)] + '...'
return value
def beacon(config):
'''
Broadcast values via zeroconf
If the announced values are static, it is advised to set run_once: True
(do not poll) on the beacon configuration.
The following are required configuration settings:
- ``servicetype`` - The service type to announce
- ``port`` - The port of the service to announce
- ``txt`` - The TXT record of the service being announced as a dict. Grains
can be used to define TXT values using one of following two formats:
- ``grains.<grain_name>``
- ``grains.<grain_name>[i]`` where i is an integer representing the
index of the grain to use. If the grain is not a list, the index is
ignored.
The following are optional configuration settings:
- ``servicename`` - Set the name of the service. Will use the hostname from
the minion's ``host`` grain if this value is not set.
- ``reset_on_change`` - If ``True`` and there is a change in TXT records
detected, it will stop announcing the service and then restart announcing
the service. This interruption in service announcement may be desirable
if the client relies on changes in the browse records to update its cache
of TXT records. Defaults to ``False``.
- ``reset_wait`` - The number of seconds to wait after announcement stops
announcing and before it restarts announcing in the case where there is a
change in TXT records detected and ``reset_on_change`` is ``True``.
Defaults to ``0``.
- ``copy_grains`` - If ``True``, Salt will copy the grains passed into the
beacon when it backs them up to check for changes on the next iteration.
Normally, instead of copy, it would use straight value assignment. This
will allow detection of changes to grains where the grains are modified
in-place instead of completely replaced. In-place grains changes are not
currently done in the main Salt code but may be done due to a custom
plug-in. Defaults to ``False``.
Example Config
.. code-block:: yaml
beacons:
avahi_announce:
- run_once: True
- servicetype: _demo._tcp
- port: 1234
- txt:
ProdName: grains.productname
SerialNo: grains.serialnumber
Comments: 'this is a test'
'''
ret = []
changes = {}
txt = {}
global LAST_GRAINS
_config = {}
list(map(_config.update, config))
if 'servicename' in _config:
servicename = _config['servicename']
else:
servicename = __grains__['host']
# Check for hostname change
if LAST_GRAINS and LAST_GRAINS['host'] != servicename:
changes['servicename'] = servicename
if LAST_GRAINS and _config.get('reset_on_change', False):
# Check for IP address change in the case when we reset on change
if LAST_GRAINS.get('ipv4', []) != __grains__.get('ipv4', []):
changes['ipv4'] = __grains__.get('ipv4', [])
if LAST_GRAINS.get('ipv6', []) != __grains__.get('ipv6', []):
changes['ipv6'] = __grains__.get('ipv6', [])
for item in _config['txt']:
changes_key = 'txt.' + salt.utils.stringutils.to_unicode(item)
if _config['txt'][item].startswith('grains.'):
grain = _config['txt'][item][7:]
grain_index = None
square_bracket = grain.find('[')
if square_bracket != -1 and grain[-1] == ']':
grain_index = int(grain[square_bracket+1:-1])
grain = grain[:square_bracket]
grain_value = __grains__.get(grain, '')
if isinstance(grain_value, list):
if grain_index is not None:
grain_value = grain_value[grain_index]
else:
grain_value = ','.join(grain_value)
txt[item] = _enforce_txt_record_maxlen(item, grain_value)
if LAST_GRAINS and (LAST_GRAINS.get(grain, '') != __grains__.get(grain, '')):
changes[changes_key] = txt[item]
else:
txt[item] = _enforce_txt_record_maxlen(item, _config['txt'][item])
if not LAST_GRAINS:
changes[changes_key] = txt[item]
if changes:
if not LAST_GRAINS:
changes['servicename'] = servicename
changes['servicetype'] = _config['servicetype']
changes['port'] = _config['port']
changes['ipv4'] = __grains__.get('ipv4', [])
changes['ipv6'] = __grains__.get('ipv6', [])
GROUP.AddService(avahi.IF_UNSPEC, avahi.PROTO_UNSPEC, dbus.UInt32(0),
servicename, _config['servicetype'], '', '',
dbus.UInt16(_config['port']), avahi.dict_to_txt_array(txt))
GROUP.Commit()
elif _config.get('reset_on_change', False) or 'servicename' in changes:
# A change in 'servicename' requires a reset because we can only
# directly update TXT records
GROUP.Reset()
reset_wait = _config.get('reset_wait', 0)
if reset_wait > 0:
time.sleep(reset_wait)
GROUP.AddService(avahi.IF_UNSPEC, avahi.PROTO_UNSPEC, dbus.UInt32(0),
servicename, _config['servicetype'], '', '',
dbus.UInt16(_config['port']), avahi.dict_to_txt_array(txt))
GROUP.Commit()
else:
GROUP.UpdateServiceTxt(avahi.IF_UNSPEC, avahi.PROTO_UNSPEC, dbus.UInt32(0),
servicename, _config['servicetype'], '',
avahi.dict_to_txt_array(txt))
ret.append({'tag': 'result', 'changes': changes})
if _config.get('copy_grains', False):
LAST_GRAINS = __grains__.copy()
else:
LAST_GRAINS = __grains__
return ret