One of the best attributes of the Antidote platform is that it takes on as much complexity as is needed on the back-end in order to provide a seamless learning experience to the user on the front-end. A big part of this is the ability to automatically configure all lesson endpoints to fit the scenario being used to teach a concept, so that when the learner is ready to take on a subject, they aren't distracted by fiddling with configurations to "prep" the lesson.
Much of this advantage is gleaned from the fact that all Endpoints are started from Docker images, which start the same way each time. All Endpoint software dependencies, configurations, scripts, etc. are built right into the image. However, it's not always possible to put everything into this image at build time. For instance, a network device can be built as a Docker image, but depending on the Lesson or Stage, might have wildly different configurations, in order to teach a particular concept. For this, Antidote offers the ability to configure Endpoints dynamically once they're started from their base image.
Don't overdo it with endpoint configuration. The fact that Antidote is powered by containers which are cryptographically guaranteed to start from the same base image each time is a huge advantage and it's useful to bake configurations into the container image wherever possible. So, use the configuration options below, but in proper balance with an already fairly functional base image configuration.
To accomplish this configuration, the Antidote project maintains a configurator image, which has all of the necessary prerequisites for performing Endpoint configuration. When Antidote needs to perform a configuration for lesson Endpoints, such as when a lesson is initially loaded, or when the user is navigating to a new Stage, Antidote will spin up one configuration pod per lesson endpoint to perform the relevant configuration steps, and will populate those pods with a few useful environment variables that can be consumed by the configuration scripts defined by the lesson author. They are described below:
| Variable | Description |
|---|---|
| ANTIDOTE_TARGET_HOST | Set to the IP address of the endpoint. Useful because this is always dynamic |
| ANSIBLE_HOST_KEY_CHECKING | Set to "False" so that Ansible is able to connect to any image if used (we don't pre-populate our images with known keys) |
Endpoints are individually configured on a per-stage basis, and the Antidote platform provides several mechanisms for accomplishing this, so lesson builders have options when it comes to configuring their Endpoints.
Specifying which configuration type you want to use for your endpoint is fairly straightforward, but there are some underlying implications you should be aware of for each option, which we'll explain below.
Usage: configurationType: napalm-<driver>
One of the most popular use cases for configuring endpoints between stages is putting a network configuration into place that's relevant to the concepts being taught. You may want to have three virtual switches in a topology but based on the stage being viewed, the configuration might need to change. This is a very common scenario.
Rather than write a custom Python script or Ansible playbook to simply load a config onto a network device, you can use the NAPALM configuration option shown here.
To use this option, you need to specify a specially formatted configurationType value. This configuration option uses the napalm-<driver> syntax, where <driver> is the name of the NAPALM driver you wish to use. For instance, if the network device is running Junos, you'll specify configurationType: napalm-junos. Anything after the hyphen is passed directly to NAPALM, so make sure you're using the right driver name.
This configuration option will look for a file with the extension .txt, which is named identically to the endpoint you wish to configure. For instance, a configuration for a device called vqfx1 will be named vqfx1.txt. A configuration file must exist for every endpoint that uses this option, in the config directory of every stage.
Some network images use IP masquerade (NAT) for the management interface, which means you don't need to worry about the IP configuration for this interface - it's usually static per that image's configuration. The "outer" address is assigned automatically from a container level, and the inner virtual machine doesn't need to worry about it. However, in some cases, NAT is not used, and you need to be able to leverage the environment passed to the configuration pod to ensure you get the right address. If this describes you, read on. If not, you can safely ignore the next paragraph.
As mentioned previously, all configuration pods are started with the environment variable SYRINGE_TARGET_HOST set to the IP address of the endpoint within Kubernetes. This is useful because this is assigned dynamically and you might want to use this in your configuration. So, instead of applying the configuration directly to the device, the configuration environment will first render the source file as a Jinja2 template. If you reference the variable mgmt_addr anywhere in the config using Jinja syntax (e.g. {{ mgmt_addr }}), it will be replaced with the IP address of the management interface. The subnet mask of this interface must be configured according to the CNI configuration in place. Normally this is a /12.
This will use NAPALM's load-merge function to load the resulting config onto the device, and commit it.
Usage: configurationType: python
If you wish, you can use a custom Python script to make the necessary configuration changes. If you specify the above configurationType value, you'll need to make sure that for every endpoint that uses this option, a file named <endpoint>.py is present in the config directory for each stage.
Usage: configurationType: ansible
If you wish, you can use an Ansible playbook to make the necessary configuration changes. If you specify the above configurationType value, you'll need to make sure that for every endpoint that uses this option, a file named <endpoint>.yml is present in the config directory for each stage for every endpoint that uses this option.