Tao Jie created HDFS-14297:
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Summary: Add cache for getContentSummary() result
Key: HDFS-14297
URL: https://issues.apache.org/jira/browse/HDFS-14297
Project: Hadoop HDFS
Issue Type: Improvement
Reporter: Tao Jie
In a large HDFS cluster, calling {{getContentSummary}} for a directory with
large amount of files is very expensive. In a certain cluster with more than
100 million files, calling {{getContentSummary}} may take more than 10s and it
will hold fsnamesystem lock for such a long time.
In our cluster, there are several peripheral systems calling
{{getContentSummary}} periodically to monitor the status of dirs. Actually we
don't need the very accurate result in most cases. We could keep a cache for
those contentSummary result in namenode, with which we could avoid repeated
heavy request in a span. Also we should add more restrictions to this cache:
1,its size should be limited and it should be LRU, 2, only result of heavy
request would be added to this cache, eg, rpctime over 1000ms.
Any thought?
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