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From Richard Sharpe <realrichardsha...@gmail.com>
Subject Re: Is zkfc (zookeeper failover controller) a Hadoop-only thing or something more general to Zookeeper?
Date Thu, 30 Apr 2015 21:51:39 GMT
On Thu, Apr 30, 2015 at 2:04 PM, Chris Nauroth <cnauroth@hortonworks.com> wrote:
> Hello Richard,
> The "hdfs zkfc" command used as part of HDFS HA is a Hadoop-specific
> solution that implements an additional layer of logic on top of a
> ZooKeeper distributed lock.  The additional logic relates to transitioning
> NameNode processes between active and standby state, and fencing of an old
> active NameNode in case it still believes itself to be active due to a
> network partition or other malfunction.  The code for this resides in the
> Hadoop project, not ZooKeeper.  It is considered a private implementation
> detail of Hadoop, not a stable public API, so I recommend against writing
> code that relies on those classes.  It might still be interesting to read
> the code as inspiration for your own implementation though.  If you're
> interested, take a look at the following spots in the Hadoop source tree:
> hadoop-hdfs-project/hadoop-hdfs/src/main/java//org/apache/hadoop/hdfs/tools
> /DFSZKFailoverController.java
> hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server
> /namenode/ha/
> hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/

Thanks for that info ...

Richard Sharpe

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