Pipe issue

jérémy HAGE hage.jeremy at gmail.com
Tue May 19 14:36:13 CEST 2015


I am encountering an issue with varnish and pipes. When the number of
backend connections achieves max_connections, varnish doesn't send any

The error message from curl is "curl: (52) Empty reply from server". That
seems to be a bug because, in my opinion Varnish is supposed to reply a 503
error at least.

It is easy to reproduce. I installed the official debian package (wheezy)
of varnish 4. Then I put this little configuration.

vcl 4.0;
backend default {
    .host = "";
    .port = "80";
    .max_connections = 1;

sub vcl_recv {
    return (pipe);

Then I made 2 simultaneous connections. To make it as simplest as possible,
I installed Apache as backend with mod_php and I added a script which only
makes a "sleep(10)". When I make 2 curl simultaneously, the second gives me
this error "curl: (52) Empty reply from server" .

Is it an expected behavior?

Best regards,
Jérémy HAGE
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