heroku.vcl

director routing_mesh round-robin {
	{
		.backend = {
			.host = "...some ip...";
			.port = "...some port...";
			.first_byte_timeout = 90s;
			.between_bytes_timeout = 90s;
		}
		# ...more backends...
	}
}

sub vcl_recv {
	set req.backend = routing_mesh;

	# POST, PUT, and DELETE are not cached
	if (req.request != "GET" && req.request != "HEAD") {
		return (pass);
	}

	# never cache when http basic auth is used
	if (req.http.Authorization) {
		return (pass);
	}

	# serve stale items for 30 seconds while fetching new item from backend
	set req.grace = 30s;

	return (lookup);
}

sub vcl_fetch {
	# cache 200s set to cache public
	if (obj.cacheable && obj.http.Cache-Control ~ "public") {
		set obj.prefetch = -30s;
		unset obj.http.set-cookie;
		return (deliver);
	}

	# everything else is served dynamically
	return (pass);
}


sub vcl_error {
	set obj.http.Content-Type = "text/html; charset=utf-8";
	synthetic {"...error page html..."};
	return (deliver);
}

# Disable keep-alive support with backends
sub vcl_miss {
	set bereq.http.Connection = "close";
}
sub vcl_pass {
	set bereq.http.Connection = "close";
}
sub vcl_pipe {
	set bereq.http.Connection = "close";
}