readme.md

Part 2

In here, we'll introduce the usage of conditional and looping statements like:

1. if-else to dynamically assign pci addresses (as opposed to a static config for pci in this template).
   The pci-addresses are assigned depending on the Hardware Type

2. for loops to shrink the template by looping through repetitive config elements.

1. If-Else

The hardware type for a given branch is stored in the variable tab / file and then compared to the entire list of possible hardware types in the if-else logic at the beginning of the template.
When a match is found, the respective pci-address variables are set for the given branch.

If the hwType on the variable is set as Silicom, the following pci addresses are assigned to the respective interface.

interface	variabes	pci address
mpls1	mpls1_pci	0000:00:04.0
lan1	lan1_pci	0000:00:03.0
wan1	wan1_pci	0000:00:05.0

For every other hardware, the following pci addresses are assinged to the respective interface

interface	variabes	pci address
mpls1	mpls1_pci	0000:00:05.0
lan1	lan1_pci	0000:00:04.0
wan1	wan1_pci	0000:00:06.0

And assigned to the interface like so

"pciAddress": {{ mpls1_pci }}
"pciAddress": {{ lan1_pci }}
"pciAddress": {{ wan1_pci }}

NOTE: In this sample, we assume there are only 2 hw types Silicom and Lanner and hence an else) If there are more hw types, you could chain them through an elsif loop

2. Shrinking repetitive config using for loops

Looking at the service routes in template, the service routes

svr-testserver2,
svr-dnat-testservice3,
svr-lb-testservice

have similar config and can be merged to self generate as seen in template and shown below.

First, we compile the list of service routes we want self generated.

{% assign service_routes = "testservice2, dnat-testservice3, lb-testservice" | split: ", " %}

NOTE: The (split: ", ") is using the ", " as delimiter and compiling a list of just the service names

If there's a need to add another service route with a similar format, all that's needed then is to add an entry to the above list.

Next, we loop through them by using a for loop

{% for service_name in service_routes %}
          {
            "name": "svr-{{ service_name }}",
            "serviceName": "{{ service_name }}",
            "peer": "{{ instance.routerName }}"
          }{% if forloop.last == false %},{% endif %}
{% endfor %}

Where the for service_name in service_routes loads each of the service routes one after the other.

The {% if forloop.last == false %},{% endif %} adds a comma for all segments but the last one.

This form of reusability helps managing the service routes a lot easier by listing out all of them in a single place at the top of the file.