fengnanli opened a new pull request #2047:
URL: https://github.com/apache/hadoop/pull/2047
Summary:
This patch is targeting improving router's performance
for delegation tokens related operations.
It achieves the goal by removing watchers from router on
tokens since based on our experience. The huge number of
watches inside Zookeeper is degrading Zookeeper's performance
pretty hard. The current limit is about 1.2-1.5 million.
Specific changes:
1. Explicitly disable the watcher to tokens by not using
PathChildrenCache or any curator provided cache at all.
2. Schedule a sync task between router and Zookeeper at
a configurable interval to make routers sync with their
token information through Zookeeper.
3. For token's change, always make sure to change local cache
first instead of depending on callbacks of the watch event
when using PathChildrenCache.
The above three points are trying to make router token cache
behaves as close as possible to the case when the PathChildrenCache
is used. The below point handles one corner case.
4. Before token remover(a background thread) removes token from
Zookeeper, one router will first make sure this token hasn't
been renewed by other peers. This happens only when somehow the
sync failed for this token that router local cache doesn't have
the corret renewal date (expiry date)
Test Plan:
1. Add several unit tests covering all common use cases.
2. Deployed on two machines and performing all tests.
3. Pressure testing: create production scale number of tokens (100k)
and monitor the sync latency.
## NOTICE
Please create an issue in ASF JIRA before opening a pull request,
and you need to set the title of the pull request which starts with
the corresponding JIRA issue number. (e.g. HADOOP-XXXXX. Fix a typo in YYY.)
For more details, please see
https://cwiki.apache.org/confluence/display/HADOOP/How+To+Contribute
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