[jboss-jira] [JBoss JIRA] Resolved: (JGRP-549) ConnectionTable: spurious Connection instances on concurrent connects

ConnectionTable: spurious Connection instances on concurrent connects --------------------------------------------------------------------- Key: JGRP-549 URL: http://jira.jboss.com/jira/browse/JGRP-549 Project: JGroups Issue Type: Bug Reporter: Bela Ban Assigned To: Bela Ban Fix For: 2.6 If we have members A and B, and they don't yet have connections to each other, and start sending messages to each other at the exact same time, then we run into the following scenario: - A attempts to connect to B (new Socket()) - B attempts to connect to A - A accepts B's connection and adds an entry for B into its table - B adds an entry for A into its table - B gets the accept() from A, but doesn't add the new Connection into its table because there is already a Connection. This leads to a spurious Connection object, which will only be closed and garbage collected once A or B leaves the cluster - We used to close Connections which were already in the table, but this lead to ping-pong effects where concurrent initial senders always closed each others connections - Even worse: a new Socket() always creates a new Connection object and places it into the table, *regardless* of whether a Connection for a given destination already exists or not ! GOAL: #1 Have only 1 TCP connection between any 2 members #2 Establish a handshaking mechanism, to avoid spurious connections SOLUTION: - When A establishes a connection to B, A needs to get agreement from B first (and vice versa)