RATIS-2719. SegmentedRaftLog.close may deadlock with the cache eviction thread. - #1617

What changes were proposed in this pull request?

SegmentedRaftLog.close() acquires the write lock before calling cacheEviction.close(), which interrupts the cache eviction thread and waits for it to terminate using Thread.join().

If the eviction thread is waiting for the same write lock, a deadlock occurs:

the closing thread waits for the eviction thread to terminate, while the eviction thread waits for the closing thread to release the lock.

Interrupting the eviction thread does not resolve this because it acquires the lock using lock().

This PR moves cacheEviction.close() before acquiring the write lock, so the closing thread waits for the eviction thread to terminate without holding the lock. The eviction thread can therefore complete its current operation and exit before the cache is closed.

What is the link to the Apache JIRA

RATIS-2719. SegmentedRaftLog.close may deadlock with the cache eviction thread.

This issue was identified while investigating a timeout in TestSegmentedRaftLog.testAppendAndRoll during a CI run. The test timed out after 100 seconds, and the following stack trace shows that the test thread was waiting in Thread.join() while closing the cache eviction thread:

java.util.concurrent.TimeoutException:
testAppendAndRoll(java.lang.Boolean, java.lang.Boolean) timed out after 100 seconds

2026-09-29 10:18:07,404 [main] WARN util.AwaitToRun
- Thread[#237,s0@group-7F137C7CB308-cacheEviction-AwaitToRun,5,main]:
  join is interrupted

java.lang.InterruptedException
    at java.base/java.lang.Object.wait0(Native Method)
    at java.base/java.lang.Object.wait(Object.java:389)
    at java.base/java.lang.Thread.join(Thread.java:1887)
    at java.base/java.lang.Thread.join(Thread.java:1963)
    at org.apache.ratis.util.AwaitToRun.close(AwaitToRun.java:102)
    at org.apache.ratis.server.raftlog.segmented.SegmentedRaftLog.close(SegmentedRaftLog.java:536)
    at org.apache.ratis.server.raftlog.segmented.TestSegmentedRaftLog.testAppendAndRoll(TestSegmentedRaftLog.java:449)

https://github.com/apache/ratis/actions/runs/36554382990/job/109359915576?pr=1615

How was this patch tested?

https://github.com/slfan1989/ratis/actions/runs/36564811620