Fastly VCL, Circa 2015

sub vcl_recv {

  if (req.http.X-OperaMini-Features || req.http.User-Agent ~ " Silk-Accelerated=true$") {
    set geoip.use_x_forwarded_for = true;
  }

  set req.http.X-Geo-Country-Code = geoip.country_code;
  set req.http.X-Real-IP = req.http.Fastly-Client-IP;

#FASTLY recv

  if (req.request != "HEAD" && req.request != "GET" && req.request != "FASTLYPURGE") {
    return(pass);
  }

  return(lookup);
}

sub vcl_fetch {
#FASTLY fetch

  if ((beresp.status == 500 || beresp.status == 503) && req.restarts < 1 && (req.request == "GET" || req.request == "HEAD")) {
    restart;
  }

  if(req.restarts > 0 ) {
    set beresp.http.Fastly-Restarts = req.restarts;
  }

  if (beresp.http.Set-Cookie) {
    set req.http.Fastly-Cachetype = "SETCOOKIE";
    return (pass);
  }

  if (beresp.http.Cache-Control ~ "private") {
    set req.http.Fastly-Cachetype = "PRIVATE";
    return (pass);
  }

  if (beresp.status == 500 || beresp.status == 503) {
    set req.http.Fastly-Cachetype = "ERROR";
    set beresp.ttl = 1s;
    set beresp.grace = 5s;
    return (deliver);
  }

  if (beresp.http.Expires || beresp.http.Surrogate-Control ~ "max-age" || beresp.http.Cache-Control ~"(s-maxage|max-age)") {
    # keep the ttl here
  } else {
    # apply the default ttl
    set beresp.ttl = 3600s;
  }

  return(deliver);
}

sub vcl_hit {
#FASTLY hit

  if (!obj.cacheable) {
    return(pass);
  }
  return(deliver);
}

sub vcl_miss {
#FASTLY miss
  return(fetch);
}

sub vcl_deliver {
#FASTLY deliver
  return(deliver);
}

sub vcl_error {
#FASTLY error
}

sub vcl_pass {
#FASTLY pass
}