TransferQueueBundler: Message to stopped node blocks the bundler thread ----------------------------------------------------------------------- Key: JGRP-2463 URL: https://issues.redhat.com/browse/JGRP-2463 Project: JGroups Issue Type: Bug Affects Versions: 4.2.1 Reporter: Dan Berindei Assignee: Bela Ban Priority: Major Fix For: 4.2.2, 5.0.0.Alpha4 {{TransferQueueBundler}} sends all the messages from a single thread. When one of the {{TP.doSend()}} calls blocks, the bundler thread no longer makes any progress, and it doesn't send messages to any destination, even if {{TP.doSend()}} is only slow for one particular destination. One example is when sending a message to a stopped node, e.g. the coordinator sending a {{LEAVE_RSP}} after the leaver has already stopped. The bundler thread calls {{TP.doSend()}}, the connection no longer exists, so it ends up calling {{BaseServer.createConnection()}}. If the stopped node's machine is no longer up or it is configured to drop messages to closed ports, the connection open blocks the bundler thread for {{TCP.sock_conn_timeout}}(default: 2s). {{UNICAST3}} also retransmits the highest sent message every {{UNICAST3.xmit_interval}} (default: 500ms), for {{UNICAST3.max_retransmit_time}}(default: 1 min), so the bundler thread will block more than once for the same message. I assume the bundler thread will also block if the transport is {{TCP}}, one of the destinations is overloaded, and the TCP connection's send buffer is full. Normally applications try to spread the workload evenly among members, but e.g. with RELAY2 not all the members will be site masters.