[LOG4J2-3472] Allow configuration of custom Disruptor WaitStrategy

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.17.2
• Fix Version/s: 2.18.0
• Component/s: Configuration, Core
• Assignee: Remko Popma
• Reporter: Remko Popma
• Created: 11/Apr/22 07:55
• Updated: 02/May/22 21:12
• Resolved: 02/May/22 21:12

Description

See also LOG4J2-2858.

Currently Log4j allows a fixed set of disruptor WaitStrategies to be configured. The current code has two drawbacks:

• the fixed set does not include all built-in WaitStrategies that the disruptor library provides
• the configuration does not allow custom implementations of the com.lmax.disruptor.WaitStrategy interface.

Proposal:

Introduce a org.apache.logging.log4j.core.async.WaitStrategyProvider interface. Users may configure instances of this interface by setting system property log4j2.asyncWaitStrategyProvider.

Proposed implementation is to modify DisruptorUtil::createWaitStrategy to check for the existence of this system property, before doing anything else. If this property exists and a class can be instantiated based on the value of this property, and the resulting WaitStrategyProvider instance provides a non-null com.lmax.disruptor.WaitStrategy instance, then this waitstrategy is returned from DisruptorUtil::createWaitStrategy. Otherwise, we fall back to the existing logic.

Note that for simplicity I do not propose to have separate system properties for Async Loggers and Async LoggerConfigs.

Issue Links

• is related to: LOG4J2-3473 Provide garbage-free default disruptor WaitStrategy
• relates to: LOG4J2-2858 More flexible configuration of WaitStrategy of Disruptor
• links to: GitHub Pull Request #824
• links to: GitHub Pull Request #830