[UIMA-1110] The default setting of prefetch=1 is causing problems

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.3AS
• Component/s: Async Scaleout
• Assignee: Eddie Epstein
• Reporter: Eddie Epstein
• Created: 12/Jul/08 12:46
• Updated: 15/Sep/09 16:02
• Resolved: 03/Feb/09 16:57

Description

The new JMX monitor occasionally shows idle times of many seconds for a scaled out remote delegate that is getting many CASes per second. Assuming the monitor is correct, the problem is that AMQ is not evenly distributing the work to all the service instances. Other recent experiences have demonstrated that uneven distribution is solved with prefetch=0.

While there is some possibility that prefetch > 0 may be useful in some situations for remote delegates, for colocated delegates there is little doubt that a prefetch greater than 0 cannot help performance and can only screw up load balancing.

prefetch=0 should be the default everywhere.