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salt/doc/topics/proxyminion/index.rst
Aditya Kulkarni 7c8f236115 Add documentation for proxy minion ssh
2015-10-19 13:30:35 -04:00

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.. _proxy-minion:
=================
Salt Proxy Minion
=================
Proxy minions are a developing Salt feature that enables controlling devices
that, for whatever reason, cannot run a standard salt-minion. Examples include
network gear that has an API but runs a proprietary OS, devices with limited
CPU or memory, or devices that could run a minion, but for security reasons,
will not.
*Proxy minions are not an "out of the box" feature*. Because there are an
infinite number of controllable devices, you will most likely have to write the
interface yourself. Fortunately, this is only as difficult as the actual
interface to the proxied device. Devices that have an existing Python module
(PyUSB for example) would be relatively simple to interface. Code to control a
device that has an HTML REST-based interface should be easy. Code to control
your typical housecat would be excellent source material for a PhD thesis.
Salt proxy-minions provide the 'plumbing' that allows device enumeration
and discovery, control, status, remote execution, and state management.
See the :doc:`Proxy Minion Walkthrough </topics/proxyminion/demo>` for an end-to-end
demonstration of a working proxy minion.
See the :doc:`Proxy Minion SSH Walkthrough </topics/proxyminion/ssh>` for an end-to-end
demonstration of a working SSH proxy minion.
New in 2015.8.2
---------------
*BREAKING CHANGE*: Adding the `proxymodule` variable to __opts__ is deprecated.
The `proxymodule` variable has been moved a new globally-injected variable
called `__proxy__`. A related configuration option called
`add_proxymodule_to_opts` has been added and defaults to `True`. In the next
major release, codenamed Boron, this variable will default to False.
In the meantime, proxies that functioned under 2015.8.0 and .1 should continue
to work under 2015.8.2. You should rework your proxy code to use `__proxy__` as
soon as possible.
The `rest_sample` example proxy minion has been updated to use `__proxy__`.
This change was made because proxymodules are a LazyLoader object, but
LazyLoaders cannot be serialized. `__opts__` gets serialized, and so things
like `saltutil.sync_all` and `state.highstate` would throw exceptions.
Also in this release, proxymodules can be stored on the master in
/srv/salt/_proxy. A new saltutil function called `sync_proxies` will transfer
these to remote proxy minions. Note that you must restart the salt-proxy
daemon to pick up these changes.
In addition, a salt.utils helper function called `is_proxy()` was added to make
it easier to tell when the running minion is a proxy minion.
New in 2015.8
-------------
Starting with the 2015.8 release of Salt, proxy processes are no longer forked off from a controlling minion.
Instead, they have their own script ``salt-proxy`` which takes mostly the same arguments that the
standard Salt minion does with the addition of ``--proxyid``. This is the id that the salt-proxy will
use to identify itself to the master. Proxy configurations are still best kept in Pillar and their format
has not changed.
This change allows for better process control and logging. Proxy processes can now be listed with standard
process management utilities (``ps`` from the command line). Also, a full Salt minion is no longer
required (though it is still strongly recommended) on machines hosting proxies.
Getting Started
---------------
The following diagram may be helpful in understanding the structure of a Salt
installation that includes proxy-minions:
.. image:: /_static/proxy_minions.png
The key thing to remember is the left-most section of the diagram. Salt's
nature is to have a minion connect to a master, then the master may control
the minion. However, for proxy minions, the target device cannot run a minion.
After the proxy minion is started and initiates its connection to the 'dumb'
device, it connects back to the salt-master and for all intents and purposes
looks like just another minion to the Salt master.
To create support for a proxied device one needs to create four things:
1. The `proxy_connection_module`_ (located in salt/proxy).
2. The `grains support code`_ (located in salt/grains).
3. :ref:`Salt modules <all-salt.modules>` specific to the controlled
device.
4. :ref:`Salt states <all-salt.states>` specific to the controlled device.
Configuration parameters
########################
Proxy minions require no configuration parameters in /etc/salt/master.
Salt's Pillar system is ideally suited for configuring proxy-minions. Proxies
can either be designated via a pillar file in pillar_roots, or through an
external pillar. External pillars afford the opportunity for interfacing with
a configuration management system, database, or other knowledgeable system that
that may already contain all the details of proxy targets. To use static files
in pillar_roots, pattern your files after the following examples, which are
based on the diagram above:
``/srv/pillar/top.sls``
.. code-block:: yaml
base:
dumbdevice1:
- dumbdevice1
dumbdevice2:
- dumbdevice2
dumbdevice3:
- dumbdevice3
dumbdevice4:
- dumbdevice4
dumbdevice5:
- dumbdevice5
dumbdevice6:
- dumbdevice6
dumbdevice7:
- dumbdevice7
``/srv/pillar/dumbdevice1.sls``
.. code-block:: yaml
proxy:
proxytype: networkswitch
host: 172.23.23.5
username: root
passwd: letmein
``/srv/pillar/dumbdevice2.sls``
.. code-block:: yaml
proxy:
proxytype: networkswitch
host: 172.23.23.6
username: root
passwd: letmein
``/srv/pillar/dumbdevice3.sls``
.. code-block:: yaml
proxy:
proxytype: networkswitch
host: 172.23.23.7
username: root
passwd: letmein
``/srv/pillar/dumbdevice4.sls``
.. code-block:: yaml
proxy:
proxytype: i2c_lightshow
i2c_address: 1
``/srv/pillar/dumbdevice5.sls``
.. code-block:: yaml
proxy:
proxytype: i2c_lightshow
i2c_address: 2
``/srv/pillar/dumbdevice6.sls``
.. code-block:: yaml
proxy:
proxytype: 433mhz_wireless
``/srv/pillar/dumbdevice7.sls``
.. code-block:: yaml
proxy:
proxytype: sms_serial
deventry: /dev/tty04
Note the contents of each minioncontroller key may differ widely based on
the type of device that the proxy-minion is managing.
In the above example
- dumbdevices 1, 2, and 3 are network switches that have a management
interface available at a particular IP address.
- dumbdevices 4 and 5 are very low-level devices controlled over an i2c bus.
In this case the devices are physically connected to machine
'minioncontroller2', and are addressable on the i2c bus at their respective
i2c addresses.
- dumbdevice6 is a 433 MHz wireless transmitter, also physically connected to
minioncontroller2
- dumbdevice7 is an SMS gateway connected to machine minioncontroller3 via a
serial port.
Because of the way pillar works, each of the salt-proxy processes that fork off the
proxy minions will only see the keys specific to the proxies it will be
handling.
Also, in general, proxy-minions are lightweight, so the machines that run them
could conceivably control a large number of devices. To run more than one proxy from
a single machine, simply start an additional proxy process with ``--proxyid``
set to the id to which you want the proxy to bind.
It is possible for the proxy services to be spread across
many machines if necessary, or intentionally run on machines that need to
control devices because of some physical interface (e.g. i2c and serial above).
Another reason to divide proxy services might be security. In more secure
environments only certain machines may have a network path to certain devices.
.. _proxy_connection_module:
Proxymodules
############
A proxy module encapsulates all the code necessary to interface with a device.
Proxymodules are located inside the salt.proxy module. At a minimum
a proxymodule object must implement the following functions:
``__virtual__()``: This function performs the same duty that it does for other
types of Salt modules. Logic goes here to determine if the module can be
loaded, checking for the presence of Python modules on which the proxy depends.
Returning ``False`` will prevent the module from loading.
``init(opts)``: Perform any initialization that the device needs. This is
a good place to bring up a persistent connection to a device, or authenticate
to create a persistent authorization token.
``shutdown()``: Code to cleanly shut down or close a connection to
a controlled device goes here. This function must exist, but can contain only
the keyword ``pass`` if there is no shutdown logic required.
``ping()``: While not required, it is highly recommended that this function also
be defined in the proxymodule. The code for ``ping`` should contact the
controlled device and make sure it is really available.
Pre 2015.8 the proxymodule also must have an ``id()`` function. 2015.8 and following don't use
this function because the proxy's id is required on the command line.
``id(opts)``: Returns a unique, unchanging id for the controlled device. This is
the "name" of the device, and is used by the salt-master for targeting and key
authentication.
Here is an example proxymodule used to interface to a *very* simple REST
server. Code for the server is in the `salt-contrib GitHub repository <https://github.com/saltstack/salt-contrib/proxyminion_rest_example>`_
This proxymodule enables "service" enumeration, starting, stopping, restarting,
and status; "package" installation, and a ping.
.. code-block:: python
# -*- coding: utf-8 -*-
'''
This is a simple proxy-minion designed to connect to and communicate with
the bottle-based web service contained in
https://github.com/saltstack/salt-contrib/proxyminion_rest_example
'''
from __future__ import absolute_import
# Import python libs
import logging
import salt.utils.http
HAS_REST_EXAMPLE = True
# This must be present or the Salt loader won't load this module
__proxyenabled__ = ['rest_sample']
# Variables are scoped to this module so we can have persistent data
# across calls to fns in here.
GRAINS_CACHE = {}
DETAILS = {}
# Want logging!
log = logging.getLogger(__file__)
# This does nothing, it's here just as an example and to provide a log
# entry when the module is loaded.
def __virtual__():
'''
Only return if all the modules are available
'''
log.debug('rest_sample proxy __virtual__() called...')
return True
# Every proxy module needs an 'init', though you can
# just put a 'pass' here if it doesn't need to do anything.
def init(opts):
log.debug('rest_sample proxy init() called...')
# Save the REST URL
DETAILS['url'] = opts['proxy']['url']
# Make sure the REST URL ends with a '/'
if not DETAILS['url'].endswith('/'):
DETAILS['url'] += '/'
def id(opts):
'''
Return a unique ID for this proxy minion. This ID MUST NOT CHANGE.
If it changes while the proxy is running the salt-master will get
really confused and may stop talking to this minion
'''
r = salt.utils.http.query(opts['proxy']['url']+'id', decode_type='json', decode=True)
return r['dict']['id'].encode('ascii', 'ignore')
def grains():
'''
Get the grains from the proxied device
'''
if not GRAINS_CACHE:
r = salt.utils.http.query(DETAILS['url']+'info', decode_type='json', decode=True)
GRAINS_CACHE = r['dict']
return GRAINS_CACHE
def grains_refresh():
'''
Refresh the grains from the proxied device
'''
GRAINS_CACHE = {}
return grains()
def service_start(name):
'''
Start a "service" on the REST server
'''
r = salt.utils.http.query(DETAILS['url']+'service/start/'+name, decode_type='json', decode=True)
return r['dict']
def service_stop(name):
'''
Stop a "service" on the REST server
'''
r = salt.utils.http.query(DETAILS['url']+'service/stop/'+name, decode_type='json', decode=True)
return r['dict']
def service_restart(name):
'''
Restart a "service" on the REST server
'''
r = salt.utils.http.query(DETAILS['url']+'service/restart/'+name, decode_type='json', decode=True)
return r['dict']
def service_list():
'''
List "services" on the REST server
'''
r = salt.utils.http.query(DETAILS['url']+'service/list', decode_type='json', decode=True)
return r['dict']
def service_status(name):
'''
Check if a service is running on the REST server
'''
r = salt.utils.http.query(DETAILS['url']+'service/status/'+name, decode_type='json', decode=True)
return r['dict']
def package_list():
'''
List "packages" installed on the REST server
'''
r = salt.utils.http.query(DETAILS['url']+'package/list', decode_type='json', decode=True)
return r['dict']
def package_install(name, **kwargs):
'''
Install a "package" on the REST server
'''
cmd = DETAILS['url']+'package/install/'+name
if 'version' in kwargs:
cmd += '/'+kwargs['version']
else:
cmd += '/1.0'
r = salt.utils.http.query(cmd, decode_type='json', decode=True)
def package_remove(name):
'''
Remove a "package" on the REST server
'''
r = salt.utils.http.query(DETAILS['url']+'package/remove/'+name, decode_type='json', decode=True)
return r['dict']
def package_status(name):
'''
Check the installation status of a package on the REST server
'''
r = salt.utils.http.query(DETAILS['url']+'package/status/'+name, decode_type='json', decode=True)
return r['dict']
def ping():
'''
Is the REST server up?
'''
r = salt.utils.http.query(DETAILS['url']+'ping', decode_type='json', decode=True)
try:
return r['dict'].get('ret', False)
except Exception:
return False
def shutdown(opts):
'''
For this proxy shutdown is a no-op
'''
log.debug('rest_sample proxy shutdown() called...')
pass
.. _grains support code:
Grains are data about minions. Most proxied devices will have a paltry amount
of data as compared to a typical Linux server. By default, a proxy minion will
have several grains taken from the host. Salt core code requires values for ``kernel``,
``os``, and ``os_family``--all of these are forced to be ``proxy`` for proxy-minions.
To add others to your proxy minion for
a particular device, create a file in salt/grains named [proxytype].py and place
inside it the different functions that need to be run to collect the data you
are interested in. Here's an example:
.. code: python::
# -*- coding: utf-8 -*-
'''
Generate baseline proxy minion grains
'''
__proxyenabled__ = ['rest_sample']
__virtualname__ = 'rest_sample'
def __virtual__():
if 'proxy' not in __opts__:
return False
else:
return __virtualname__
def kernel():
return {'kernel':'proxy'}
def os():
return {'os':'proxy'}
def location():
return {'location': 'In this darn virtual machine. Let me out!'}
def os_family():
return {'os_family': 'proxy'}
def os_data():
return {'os_data': 'funkyHttp release 1.0.a.4.g'}
The __proxyenabled__ directive
------------------------------
Salt execution modules, by, and large, cannot "automatically" work
with proxied devices. Execution modules like ``pkg`` or ``sqlite3`` have no
meaning on a network switch or a housecat. For an execution module to be
available to a proxy-minion, the ``__proxyenabled__`` variable must be defined
in the module as an array containing the names of all the proxytypes that this
module can support. The array can contain the special value ``*`` to indicate
that the module supports all proxies.
If no ``__proxyenabled__`` variable is defined, then by default, the
execution module is unavailable to any proxy.
Here is an excerpt from a module that was modified to support proxy-minions:
.. code-block:: python
__proxyenabled__ = ['*']
[...]
def ping():
if not salt.utils.is_proxy():
return True
else:
ping_cmd = __opts__['proxy']['proxytype'] + '.ping'
if __opts__.get('add_proxymodule_to_opts', False):
return __opts__['proxymodule'][ping_cmd]()
else:
return __proxy__[ping_cmd]()
And then in salt.proxy.rest_sample.py we find
.. code-block:: python
def ping():
'''
Is the REST server up?
'''
r = salt.utils.http.query(DETAILS['url']+'ping', decode_type='json', decode=True)
try:
return r['dict'].get('ret', False)
except Exception:
return False
.. toctree::
:maxdepth: 2
:glob:
demo
SSH Proxymodules
----------------
See above for a general introduction to writing proxy modules.
All of the guidelines that apply to REST are the same for SSH.
This sections specifically talks about the SSH proxy module and
explains the working of the example proxy module ``ssh_sample``.
Here is a simple example proxymodule used to interface to a device over SSH.
Code for the SSH shell is in the `salt-contrib GitHub repository <https://github.com/saltstack/salt-contrib/proxyminion_ssh_example>`_
This proxymodule enables "package" installation.
.. code-block:: python
# -*- coding: utf-8 -*-
'''
This is a simple proxy-minion designed to connect to and communicate with
a server that exposes functionality via SSH.
This can be used as an option when the device does not provide
an api over HTTP and doesn't have the python stack to run a minion.
'''
from __future__ import absolute_import
# Import python libs
import json
import logging
# Import Salt's libs
from salt.utils.vt_helper import SSHConnection
from salt.utils.vt import TerminalException
# This must be present or the Salt loader won't load this module
__proxyenabled__ = ['ssh_sample']
DETAILS = {}
# Want logging!
log = logging.getLogger(__file__)
# This does nothing, it's here just as an example and to provide a log
# entry when the module is loaded.
def __virtual__():
'''
Only return if all the modules are available
'''
log.info('ssh_sample proxy __virtual__() called...')
return True
def init(opts):
'''
Required.
Can be used to initialize the server connection.
'''
try:
DETAILS['server'] = SSHConnection(host=__opts__['proxy']['host'],
username=__opts__['proxy']['username'],
password=__opts__['proxy']['password'])
# connected to the SSH server
out, err = DETAILS['server'].sendline('help')
except TerminalException as e:
log.error(e)
return False
def shutdown(opts):
'''
Disconnect
'''
DETAILS['server'].close_connection()
def parse(out):
'''
Extract json from out.
Parameter
out: Type string. The data returned by the
ssh command.
'''
jsonret = []
in_json = False
for ln_ in out.split('\n'):
if '{' in ln_:
in_json = True
if in_json:
jsonret.append(ln_)
if '}' in ln_:
in_json = False
return json.loads('\n'.join(jsonret))
def package_list():
'''
List "packages" by executing a command via ssh
This function is called in response to the salt command
..code-block::bash
salt target_minion pkg.list_pkgs
'''
# Send the command to execute
out, err = DETAILS['server'].sendline('pkg_list')
# "scrape" the output and return the right fields as a dict
return parse(out)
def package_install(name, **kwargs):
'''
Install a "package" on the REST server
'''
cmd = 'pkg_install ' + name
if 'version' in kwargs:
cmd += '/'+kwargs['version']
else:
cmd += '/1.0'
# Send the command to execute
out, err = DETAILS['server'].sendline(cmd)
# "scrape" the output and return the right fields as a dict
return parse(out)
def package_remove(name):
'''
Remove a "package" on the REST server
'''
cmd = 'pkg_remove ' + name
# Send the command to execute
out, err = DETAILS['server'].sendline(cmd)
# "scrape" the output and return the right fields as a dict
return parse(out)
Connection Setup
################
The ``init()`` method is responsible for connection setup. It uses the ``host``, ``username`` and ``password`` config variables defined in the pillar data. The ``prompt`` kwarg can be passed to ``SSHConnection`` if your SSH server's prompt differs from the example's prompt ``(Cmd)``. Instantiating the ``SSHConnection`` class establishes an SSH connection to the ssh server (using Salt VT).
Command execution
#################
The ``package_*`` methods use the SSH connection (established in ``init()``) to send commands out to the SSH server. The ``sendline()`` method of ``SSHConnection`` class can be used to send commands out to the server. In the above example we send commands like ``pkg_list`` or ``pkg_install``. You can send any SSH command via this utility.
Output parsing
##############
Output returned by ``sendline()`` is a tuple of strings representing the stdout and the stderr respectively. In the toy example shown we simply scrape the output and convert it to a python dictionary, as shown in the ``parse`` method. You can tailor this method to match your parsing logic.
Connection teardown
###################
The ``shutdown`` method is responsible for calling the ``close_connection()`` method of ``SSHConnection`` class. This ends the SSH connection to the server.
For more information please refer to class `SSHConnection`_.
.. toctree::
:maxdepth: 2
:glob:
ssh
.. _SSHConnection: https://github.com/saltstack/salt/blob/b8271c7512da7e048019ee26422be9e7d6b795ab/salt/utils/vt_helper.py#L28
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