| Subject: | Interaction between keep-alive, http 1.0 client and 1.1 server |
| Date: | Thu, 14 May 2015 14:33:43 +0100 (BST) |
| To: | bug-Net-HTTP [...] rt.cpan.org |
| From: | "P. Benie" <pjb1008 [...] cam.ac.uk> |
Hi,
I've got a problem getting keep-alives to work with an XML-RPC client that
I believe to be due to a bug in Net::HTTP. I'm using version 6.06, but I
can't see any significant differences in this area between that version
and the latest, 6.08_002.
What's happening is this:
1st request
-----------
Client make a connection to the server.
Client sends request in HTTP/1.0 with Keep-Alive: 300 and Connection: Keep-Alive.
Server sends response in HTTP/1.1 with Connection: Keep-Alive.
2nd request
-----------
Client sends request in HTTP/1.0 with no Keep-Alive: or Connection: headers.
Server sends response in HTTP/1.1 with no Connection: Keep-Alive.
3rd request
-----------
Client discovers that the socket is marked readable (I think the server
has closed the connection already) so it closes the connection.
Client makes a new connection to the server.
Client sends request in HTTP/1.0 with Keep-Alive: 300 and Connection: Keep-Alive.
Server sends response in HTTP/1.1 with Connection: Keep-Alive.
etc.
4th request
-----------
Client sends request in HTTP/1.0 with no Keep-Alive: or Connection: headers.
Server sends response in HTTP/1.1 with no Connection: Keep-Alive.
The behaviour is that the client alternates between using, and not using,
keep-alives.
The server's first response is 1.1 and without Connection: close so the
socket is legitimately considered for re-use. However, the client doesn't
explicitly request on the next request Keep-Alive because the server is
1.1. The server's second response results in the connection being closed
because the client is 1.0 and it didn't request keep-alive. I think the
server is behaving correctly, and that is was an error not to emit
Connection: keep-alive when making a 1.0 request.
The relevant section of code is this: (Net/HTTP/Methods.pm)
unless (grep lc($_) eq "close", @connection) {
if ($self->keep_alive) {
if ($peer_ver eq "1.0") {
# from looking at Netscape's headers
push(@h2, "Keep-Alive: 300");
unshift(@connection, "Keep-Alive");
}
}
else {
push(@connection, "close") if $ver ge "1.1";
}
}
If I've understood LWP correctly, the fact that the socket was deposited
into the connection cache at all means that the socket is eligible for
re-use. It doesn't need further tests because it was put there by
LWP::Protocol::http.pm on the basis of the http version and connection
header in the response.
In Net/HTTP/Methods.pm, I believe that it is only necessary to focus on how
to advertise that we would like the next response to keep the
connection open, so the test, 'if ($peer_ver eq "1.0")', should actually
be looking at the http version _we_ are using, not the version that the
peer is using. In other words, the code above should be along the lines of:
if ($self->keep_alive && $ver eq '1.0') {
push(@h2, "Keep-Alive: 300");
unshift(@connection, "Keep-Alive");
}
Peter