gistfile1.txt

sub vcl_fetch {
  # Enable grace period
  set beresp.grace = 1h; 

  # Add X-Cacheable header to track cache miss reasons
  if (beresp.http.Set-Cookie) {
    set beresp.http.X-Cacheable = "NO:Set-Cookie";
  } elseif (beresp.http.Pragma ~ "no-cache") {
    set beresp.http.X-Cacheable = "NO:Pragma=no-cache";
  } elseif (beresp.http.Pragma ~ "no-store") {
    set beresp.http.X-Cacheable = "NO:Pragma=no-store";
  } elseif (beresp.http.Cache-Control ~ "no-cache") {
    set beresp.http.X-Cacheable = "NO:Cache-Control=no-cache";
  } elseif (beresp.http.Cache-Control ~ "max-age=0") {
    set beresp.http.X-Cacheable = "NO:Cache-Control=max-age=0";
  } elseif (beresp.http.Cache-Control ~ "private") {
    set beresp.http.X-Cacheable = "NO:Cache-Control=private";
  } elseif (!beresp.cacheable) {
    set beresp.http.X-Cacheable = "NO:Not Cacheable";
  } else {
    set beresp.http.X-Cacheable = "YES";

    return(deliver);
  }

  return(pass);
}