Redirect all png requests as jpg requests in Varnish

Question

I want to redirect all .png requests to .jpg requests in Varnish VCL Example: http://example.com/images/boy.png (or .PNG) to http://example.com/images/boy.jpg in Varnish VCL

Answer 1

There can be 2 cases.

A. Client redirection [1], use this in case you want to tell client's browser that the image has been moved:

sub vcl_recv {
  # ...
  if (req.url ~ "(?i)\.png$") {
    error 750 "http://" + req.host + regsub(req.url, "(?i)\.png$", ".jpg$");
  }
  # ...
}

sub vcl_error {
  # ...
  if (obj.status == 750) {
    set obj.http.Location = obj.response;
    set obj.status = 302;
    return(deliver);
  }
  # ...
}

B. Server side rewrite [2], use this in case you want to internally change the request without telling the client:

sub vcl_recv {
  # ...
  if (req.url ~ "(?i)\.png$") {
    set req.url = regsub(req.url, "(?i)\.png$", ".jpg$");
  }
  # ...
}

PD: Please don't duplicate your questions

[1] https://www.varnish-cache.org/trac/wiki/VCLExampleRedirectInVCL

[2] https://www.varnish-cache.org/trac/wiki/RedirectsAndRewrites