Overview

This repository contains the Juju layer that represents a working example of a proxy charm.

What is a proxy charm?

A proxy charm is a limited type of charm that does not interact with software running on the same host, such as controlling and configuring a remote device (a static VM image, a router/switch, etc.). It cannot take advantage of some of Juju's key features, such as scaling, relations, and leadership.

Proxy charms are primarily a stop-gap, intended to prototype quickly, with the end goal being to develop it into a full-featured charm, which installs and executes code on the same machine as the charm is running.

Usage

# Clone this repository
git clone https://osm.etsi.org/gerrit/osm/juju-charms
cd juju-charms

# Setup environment variables
source juju-env.sh

cd layers/pingpong
charm build

# Examine the built charm
cd ../../builds/pingpong
ls
actions       config.yaml  icon.svg    metadata.yaml     tests
actions.yaml  copyright    layer.yaml  reactive          tox.ini
bin           deps         lib         README.md         wheelhouse
builds        hooks        Makefile    requirements.txt

You can view a screencast of this: https://asciinema.org/a/96738

The charm build process combines this pingpong layer with each layer that it has included in the metadata.yaml file, along with their various dependencies.

This built charm is what will then be used by the SO to communicate with the VNF.

Configuration

The pingpong charm has several configuration properties that can be set via the SO:

ssh-hostname
ssh-username
ssh-password
ssh-private-key
mode

The ssh-* keys are included by the sshproxy layer, and enable the charm to connect to the VNF image.

The mode key must be one of two values: ping or pong. This informs the charm as to which function it is serving.

Contact Information

For support, please send an email to the OSM Tech list.

Integration

After you've created your charm, open interfaces.yaml and add layer:sshproxy to the includes stanza, as shown below:

includes: ['layer:basic', 'layer:sshproxy']

Reactive states

This layer will set the following states:

sshproxy.configured This state is set when SSH credentials have been supplied to the charm.

Example

In reactive/mycharm.py, you can add logic to execute commands over SSH. This example is run via a start action, and starts a service running on a remote host.

...
import charms.sshproxy


@when('sshproxy.configured')
@when('actions.start')
def start():
    """ Execute's the command, via the start action` using the
    configured SSH credentials
    """
    sshproxy.ssh("service myservice start")

Actions

This layer includes a built-in run action useful for debugging or running arbitrary commands:

$ juju run-action mycharm/0 run command=hostname
Action queued with id: 014b72f3-bc02-4ecb-8d38-72bce03bbb63

$ juju show-action-output 014b72f3-bc02-4ecb-8d38-72bce03bbb63
results:
  output: juju-66a5f3-11
status: completed
timing:
  completed: 2016-10-27 19:53:49 +0000 UTC
  enqueued: 2016-10-27 19:53:44 +0000 UTC
  started: 2016-10-27 19:53:48 +0000 UTC

Known Limitations and Issues

Security issues

Password and key-based authentications are supported, with the caveat that both (password and private key) are stored plaintext within the Juju controller.

Configuration and Usage

This layer adds the following configuration options:

ssh-hostname
ssh-username
ssh-password
ssh-private-key

Once configure those values at any time. Once they are set, the sshproxy.configured state flag will be toggled:

juju deploy mycharm ssh-hostname=10.10.10.10 ssh-username=ubuntu ssh-password=yourpassword

juju deploy mycharm ssh-hostname=10.10.10.10 ssh-username=ubuntu ssh-private-key="cat `~/.ssh/id_rsa`"

Contact Information

Homepage: https://github.com/AdamIsrael/layer-sshproxy