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Date: Thu, 30 Apr 2015 14:51:39 -0700
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Subject: Re: Is zkfc (zookeeper failover controller) a Hadoop-only thing or
 something more general to Zookeeper?
From: Richard Sharpe <realrichardsharpe@gmail.com>
To: user@zookeeper.apache.org
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On Thu, Apr 30, 2015 at 2:04 PM, Chris Nauroth <cnauroth@hortonworks.com> w=
rote:
> 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 transitionin=
g
> NameNode processes between active and standby state, and fencing of an ol=
d
> 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/too=
ls
> /DFSZKFailoverController.java
> hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/serv=
er
> /namenode/ha/
> hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/

Thanks for that info ...

--=20
Regards,
Richard Sharpe
(=E4=BD=95=E4=BB=A5=E8=A7=A3=E6=86=82=EF=BC=9F=E5=94=AF=E6=9C=89=E6=9D=9C=
=E5=BA=B7=E3=80=82--=E6=9B=B9=E6=93=8D)