gistfile1.c

/* Set the backend / origin server. */
backend default {
.host = "hostname.of.website";
.port = "80";
  /* Probe for healthiness of backend. */
  /* After 8 passing requests, it marks it as available. */
  .probe = {
    .url = "/probe.html";
    .timeout = 5 s;
    .interval = 10 s;
    .window = 10;
    .threshold = 8;
    .initial = 10;
  }
}
sub vcl_recv {
  /* Set the Host header of the backend */
  set req.http.Host = "hostname.of.website";
  
  if (req.backend.healthy) {
    /* 5 minutes TTL on all content */
    set req.grace = 300s;
  } else {
    /* If you can't get to the backend - 1 hour grace. */
    set req.grace = 1h;
  }

  /* If it's a strange request - pipe it through. */
  if (req.request != "GET" &&
    req.request != "HEAD" &&
    req.request != "PUT" &&
    req.request != "POST" &&
    req.request != "TRACE" &&
    req.request != "OPTIONS" &&
    req.request != "DELETE") {
      /* Non-RFC2616 or CONNECT which is weird. */
      return (pipe);
  }

  /* We only deal with GET and HEAD by default */
  if (req.request != "GET" && req.request != "HEAD") {
      return (pass);
  } 
  
  /* If they request the CMS - send them to the backend directly. */
  if (req.request == "GET" && req.url ~ "^/cms-directory/") {
     error 750 "Moved Temporarily";
  }

  return(lookup);
} 

sub vcl_error {
    if (obj.status == 750) {
        set obj.http.Location = "http://hostname.of.website/cms-directory/";
        set obj.status = 302;
        return(deliver);
    }
}  

sub vcl_fetch {
   /* 5 minutes TTL on all content */
   set beresp.ttl = 300s;
   
   /* If you can't get to the backend - 1 hour grace. */
   set beresp.grace = 1h;
}