Reopening IndexReader may lead to memory leak

Summary

Reopening IndexReader may lead to memory leak and causing additional pressure on JVM this may.

Error:

Error while resetting searcher: ISSUE message: this IndexReader is closed
org.apache.lucene.store.AlreadyClosedException: this IndexReader is closed
	at org.apache.lucene.index.IndexReader.ensureOpen(IndexReader.java:263)

or this line is present it the logs

"Tried to reopen the IndexReader, but it threw AlreadyClosedException. Opening a fresh IndexReader."

Steps to Reproduce

This is not guaranteed to reproduce the bug.

1. Run background reindex 
2. Do many search requests

Expected Results

Jira handles reopen of IndexReader gracefully. 

Actual Results

After one of the above two errors happen Jira is opening another fresh copy of IndexReader from disk. This result in all Lucene memory caches being duplicated. In most cases those structures occupy several GB or RAM which results in either OutOfMemoryError or memory pressure and full GC events being triggered. 

Notes

This is happening because of concurrency bug in com.atlassian.jira.index.DelayCloseable.Helper

Example of leak in DelayCloseSearcher"

Workaround

Restart JIRA