[ZOOKEEPER-140] Deadlock in QuorumCnxManager

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.0
• Fix Version/s: 3.0.0
• Assignee: Flavio Paiva Junqueira
• Reporter: Flavio Paiva Junqueira
• Created: 13/Sep/08 10:02
• Updated: 26/Oct/08 01:10
• Resolved: 01/Oct/08 09:21

Description

Frequently the servers deadlock in QuorumCnxManager:initiateConnection on
s.read(msgBuffer) when reading the challenge from the peer.

Calls to initiateConnection and receiveConnection are synchronized, so only one or the other can be executing at a time. This prevents two connections from opening between the same pair of servers.

However, it seems that this leads to deadlock, as in this scenario:

A (initiate --> B)
B (initiate --> C)
C (initiate --> A)

initiateConnection can only complete when receiveConnection runs on the remote peer and answers the challenge. If all servers are blocked in initiateConnection, receiveConnection never runs and leader election halts.

Issue Links

• blocks: ZOOKEEPER-127 Use of non-standard election ports in config breaks services