Question about first_byte_timeout and ESI

Tue Apr 26 15:11:40 CEST 2011

Hi there.

I've been playing with first_byte_timeout parameter.

Supposing the following script:

<?
       sleep(10);
       echo ('hi there');

And a simplified VCL like this:

backend test {
        .host = "x.x.x.x";
        .port = "80";
        .first_byte_timeout = 1200ms;
}

sub vcl_recv {
                set req.backend = test;
                return(pass);
}

sub vcl_fetch {
                esi;
}

When I request http://test/sleep.php after 1200 milli seconds Varnish
returns a 503, this is the expected behaviour.

But, when we have an html with esi code like this:

<html>
<body>
        <esi:include src="/sleep.php"/>
</body>
</html>

When I request http://test/test.html, the 503 is thrown after 2400
milliseconds. As you can see is exactly double of first_byte_timeout.
If other esi:included is set, the elapsed time goes to 3600
milliseconds, and so on.

My question, is this the expected behaviour ????

Thanks in advance.
Kind Regards.