[LOG4J2-1719] StringBuilderFormattable Messages should used cached formatted message if it exists

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.7
• Fix Version/s: 2.8
• Component/s: API
• Assignee: Remko Popma
• Reporter: Remko Popma
• Created: 20/Nov/16 14:59
• Updated: 20/Nov/16 15:51
• Resolved: 20/Nov/16 15:51

Description

When logging asynchronously, Message::getFormattedMessage is called to give Message implementations a chance to take a snapshot of mutable objects before the message is passed to another thread. (See LOG4J2-763, LOG4J2-1718. Exceptions are Messages implementing ReusableMessage or AsynchronouslyFormattable.)

Some Messages implement StringBuilderFormattable to avoid creating temporary objects in the Layout.

The StringBuilderFormattable::formatTo(StringBuilder) method should be implemented such that it first checks if a cached formatted message string exists. If so, this string should be appended to the StringBuilder. If no cached message string exists logging is done synchronously and the formatted message can safely be created afresh.

This bug exists in:

• ObjectMessage
• SimpleMessage