vhost headers interpolate string as variable

[zilchms]

Describe the Bug

I am trying to set a header for a vhost I am declaring with hiera.
The header is:
Header add Set-Cookie "ROUTEID=.%{BALANCER_WORKER_ROUTE}e; path=/" env=BALANCER_ROUTE_CHANGED
To achieve this, I put the following into the hiera:

apache::vhosts:
  'url-com-ssl':
    servername: 'url.com'
    headers:
      - 'add Set-Cookie \"ROUTEID=.%{BALANCER_WORKER_ROUTE}e; path=/\" env=BALANCER_ROUTE_CHANGED'

This results in:
Header add Set-Cookie "ROUTEID=.e; path=/" env=BALANCER_ROUTE_CHANGED

It seems that the module/template interpolates the variable in the single quoted string resulting in an empty substring. This would make it hard/impossible to use the environment variables functionalities of apache.

I tried several different ways to escape the %{BALANCER_WORKER_ROUTE} part, but had no success.
Maybe there is a way I am not aware of? Help is much appreciated.

Expected Behavior

I expected the apache module to set the header correctly without interpolating the string before writing it into the file.

Steps to Reproduce

1. Setup the apache-module on the puppetmaster with hiera as described above
2. Run the agent
3. View the resulting output file

Environment

• Module-Version 8.2.0
• Platform SLES 12-SP5 (both master and agent)
• Puppetversion 6.28.0
• Puppetserver Version 6.20.0

Additional Context

If there is a way to correctly escape or configure variables in headers, it is not really apparent from the docs. Maybe there needs to be a bit more documentation, if this is not a bug?

[chutzimir]

The solution to your problem is literally implemented with a literal function documented here: https://www.puppet.com/docs/puppet/7/hiera_merging.html#interpolation_functions-literal-function

The following is quoting the above section:

The literal function

The literal interpolation function lets you escape a literal percent sign (%) in Hiera data, to avoid triggering interpolation where it isn’t wanted.

This is useful when dealing with Apache config files, for example, which might include text such as %{SERVER_NAME}. For example:

server_name_string: "%{literal('%')}{SERVER_NAME}"

The value of server_name_string would be %{SERVER_NAME}, and Hiera would not attempt to interpolate a variable named SERVER_NAME.

The only legal argument for literal is a single % sign.

[zilchms]

Thanks for the hint, I will test of that works for my setup :)

[Ramesh7]

Thanks @chutzimir for your pointers.
BTW @zilchms I have tried with literal and it worked for me, here is hiera values which I put :

    headers:
      - 'add Set-Cookie "ROUTEID=.%{literal("%")}{BALANCER_ROUTE_CHANGED}e; path=/" env=BALANCER_ROUTE_CHANGED'

And in vhost config file below is output I got :

Header add Set-Cookie "ROUTEID=.%{BALANCER_ROUTE_CHANGED}e; path=/" env=BALANCER_ROUTE_CHANGED

Using literal we don't need escape, this works like charm.