Colin Patrick McCabe created HADOOP-10077:
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Summary: o.a.h.s.Groups should refresh in the background
Key: HADOOP-10077
URL: https://issues.apache.org/jira/browse/HADOOP-10077
Project: Hadoop Common
Issue Type: Bug
Affects Versions: 2.2.1
Reporter: Colin Patrick McCabe
Assignee: Colin Patrick McCabe
{{org.apache.hadoop.security.Groups}} maintains a cache of mappings between
user names and sets of associated group names. Periodically, the entries in
this cache expire and must be refetched from the operating system.
Currently, this is done in the context of whatever thread happens to try to
access the group mapping information right after the time period expires.
However, this is problematic, since that thread may be holding the
{{FSNamesystem}} lock. This means that if the {{GroupMappingServiceProvider}}
is slow, the whole NameNode may grind to a halt until it finishes. This can
generate periodic load spikes or even NameNode failovers.
Instead, we should allow the refreshing of the group mappings to be done
asynchronously in a background thread pool.
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