[LUCENE-1186] [PATCH] Clear ThreadLocal instances in close()

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.3, 2.3.1, 2.4
• Fix Version/s: 2.4.1, 2.9

Environment

any

• Lucene Fields: New, Patch Available
• Assignee: Michael McCandless
• Reporter: Christian Kohlschütter
• Created: 22/Feb/08 10:54
• Updated: 28/Aug/22 11:46
• Resolved: 02/Mar/09 16:44

Description

As already found out in LUCENE-436, there seems to be a garbage collection problem with ThreadLocals at certain constellations, resulting in an OutOfMemoryError.
The resolution there was to remove the reference to the ThreadLocal value when calling the close() method of the affected classes (see FieldsReader and TermInfosReader).
For Java < 5.0, this can effectively be done by calling threadLocal.set(null); for Java >= 5.0, we would call threadLocal.remove()

Analogously, this should be done in any class which creates ThreadLocal values

Right now, two classes of the core API make use of ThreadLocals, but do not properly remove their references to the ThreadLocal value
1. org.apache.lucene.index.SegmentReader
2. org.apache.lucene.analysis.Analyzer

For SegmentReader, I have attached a simple patch.
For Analyzer, there currently is no patch because Analyzer does not provide a close() method (future to-do?)