[QPID-6387] ChannelToSessionMap/IdToConsumerMap array optimisation publishes in thread unsafe manner

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.18, 0.22, 0.30
• Fix Version/s: 0.31
• Component/s: JMS AMQP 0-x
• Assignee: Keith Wall
• Reporter: Keith Wall
• Created: 11/Feb/15 22:23
• Updated: 02/Oct/19 19:21
• Resolved: 12/Feb/15 16:34

Description

Two internal classes within the Java Client (ChannelToSessionMap / IdToConsumerMap) use an optimisation which hopes to permit 'fast access' first sixteen sessions (or consumers) by making use on an array. The array is written by one thread and then read by others. Unfortunately, the read/writes are not protected using a memory barrier so it is possible a thread may see a stale value, and this could lead to incorrect program behaviour.

It is safer (and simpler) to replace the data structure with one backed by a ConcurrentHashMap.