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.
- relates to
HADOOP-8088 User-group mapping cache incorrectly does negative caching on transient failures