Salt Proxy Minion¶

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

base:
  dumbdevice1:
    - dumbdevice1
  dumbdevice2:
    - dumbdevice2
  dumbdevice3:
    - dumbdevice3
  dumbdevice4:
    - dumbdevice4
  dumbdevice5:
    - dumbdevice5
  dumbdevice6:
    - dumbdevice6
  dumbdevice7:
    - dumbdevice7

/srv/pillar/dumbdevice1.sls

proxy:
  proxytype: networkswitch
  host: 172.23.23.5
  username: root
  passwd: letmein

/srv/pillar/dumbdevice2.sls

proxy:
  proxytype: networkswitch
  host: 172.23.23.6
  username: root
  passwd: letmein

/srv/pillar/dumbdevice3.sls

proxy:
  proxytype: networkswitch
  host: 172.23.23.7
  username: root
  passwd: letmein

/srv/pillar/dumbdevice4.sls

proxy:
  proxytype: i2c_lightshow
  i2c_address: 1

/srv/pillar/dumbdevice5.sls

proxy:
  proxytype: i2c_lightshow
  i2c_address: 2

/srv/pillar/dumbdevice6.sls

proxy:
  proxytype: 433mhz_wireless

/srv/pillar/dumbdevice7.sls

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.

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

This proxymodule enables "service" enumeration, starting, stopping, restarting, and status; "package" installation, and a ping.

# -*- 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 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:

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.