Dong Lin created KAFKA-6172:
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Summary: Cache lastEntry in TimeIndex to avoid unnecessary disk
access
Key: KAFKA-6172
URL: https://issues.apache.org/jira/browse/KAFKA-6172
Project: Kafka
Issue Type: Improvement
Reporter: Dong Lin
Assignee: Dong Lin
LogSegment.close() calls timeIndex.maybeAppend(...), which in turns make a
number of calls to timeIndex.lastEntry(). Currently timeIndex.lastEntry()
involves disk seek operation because it tries to read the content of the last
few bytes of the index files on the disk. This slows down the broker shutdown
process.
For a given broker of 6k partitions and 19k segments, we find that
LogManager.shutdown() takes 15 minutes. The broker is configured to use 10
threads to close log in parallel. According to the thread dump taken while the
broker is in the process of LogManager.shutdown(), roughly 5 out of the 10
threads are in RUNNABLE state at TimeIndex.lastEntry(). This suggests that
TimeIndex.lastEntry() is very likely costing a lot of shutdown time.
This patch intends to reduce the broker shutdown time by caching the lastEntry
in memory so that broker does not have to always read disk to get the lastEntry.
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