Close a TCP connection when indicated by Connection: Close header.

[mikkokar]

Introduction

Close the TCP connection when indicated by Connection: close header in the received response.

Background

So far, Styx has ignored the received Connection: close header, and relied on sender to close the TCP connection, and on Netty to deliver a channelInactive event. This behaviour introduces a race condition that subtly increases failed requests manifesting in Styx 502 responses.

This behaviour unnecessarily delays the connection removal, and is a problematic specifically with pooled connections. A pooled connection may be reused for another request wile the operating system and/or TCP protocol is processing connection closure (transmitting FIN). When a request is sent on such a connection, it will be rejected by the remote peer, resulting in a TCP reset.

Solution

Check if the Connection: close header is present in a response. If so, close the connection straight away. This taints the connection so that it won't be used for any future requests, eliminating the race condition.