Sijie Guo created DL-101:
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Summary: Improve session expire handling on fetching log segments
for readers
Key: DL-101
URL: https://issues.apache.org/jira/browse/DL-101
Project: DistributedLog
Issue Type: Improvement
Components: distributedlog-core
Reporter: Sijie Guo
Assignee: Sijie Guo
The log segment management in DL is now done by 3 parts.
- a LogSegmentMetadataStore (one per namespace instance): it is used for
fetching the log segments from log segment metadata store (ZooKeeper). it
doesn't do any caching.
- a LogSegmentMetadataCache (one per namespace instance): it is a guava
cache based metadata cache. it maintains a mapping between log segment metadata
path and the log segment metadata. it manages the cache for the log segments
that will be accessed in this namespace instance. it doesn't manage the
sequence of the log segments for streams.
- a PerStreamLogSegmentCache for each BKLogHandler. the log segment cache
is per stream. it maintains the sequence of the log segments.
BKLogWriteHandler doesn't watch the log segment changes. It fetches minimal
number of log segments when it is created and fetches the full list of log
segments for truncations. New log segments will be added to the per stream log
segment cache with log segment rolling.
BKLogReadHandler watch the log segments changes and only notify when the
list of log segments is changed. the session handling which is specific to the
metadata store is hidden to the implementations of LogSegmentMetadataStore.
The change tries to cleanup bunch of unused methods in
BKLog{Read,Write}Handler too.
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