Response packet caching for get request
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Key: ZOOKEEPER-1429
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1429
Project: ZooKeeper
Issue Type: Improvement
Components: server
Affects Versions: 3.4.3
Reporter: Thawan Kooburat
Priority: Minor
Motivation:
In our scalability testing, we have a large number of clients watching for data
changes. All of them fetch data immediately when a watch is fired. We found
that GC consumes significant amount of CPU time in this scenario. In our
prototype, we added packet caching for getData() request and found that GC time
reduced by 40%. GC that we used is Concurrent Mark Sweep Collector.
Design and Implementation:
Similar to our prototype, we plan to add packet caching for getData() request
using LRU caching. The cache stores serializes response (data + stat) in form
of ByteBuffer indexed by its pathname. The cache entry is invalidated when
there is a set request that affect the data.
The data structure that we plan to use for LRU cache is CacheBuilder
[http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/cache/CacheBuilder.html]
because it provides many tunable features that we try and use in the future.
Currently, the eviction policy will be based on memory size. Otherwise, we can
implement it using LinkedHashMap if we do not want to rely on external library.
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