Andrew Wang created HDFS-5369:
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             Summary: Support negative caching of user-group mapping
                 Key: HDFS-5369
                 URL: https://issues.apache.org/jira/browse/HDFS-5369
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: namenode
    Affects Versions: 2.2.0
            Reporter: Andrew Wang


We've seen a situation at a couple of our customers where interactions from an 
unknown user leads to a high-rate of group mapping calls. In one case, this was 
happening at a rate of 450 calls per second with the shell-based group mapping, 
enough to severely impact overall namenode performance and also leading to 
large amounts of log spam (prints a stack trace each time).

Let's consider negative caching of group mapping, as well as quashing the rate 
of this log message.



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