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https://issues.apache.org/jira/browse/HADOOP-10641?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14059130#comment-14059130
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Konstantin Shvachko commented on HADOOP-10641:
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Sorry if it sounded as an overreaction, non intended.
??doing this work on a branch??
There is no resistance. The plan has always been to build CNode on a branch. I
am just trying to optimize development of CNode and HBase region replication,
which is going on in parallel. My thinking was to commit the CE interface to
trunk and then branch off HDFS of it. That way both both HDFS and HBase can use
the interface.
??the primary goal of this work is to introduce a plugin point for WANdisco's
coordination engine implementation??
I don't see anything bad with plugging in WANdisco CE into Hadoop, [as I argued
in the other jira
comment|https://issues.apache.org/jira/browse/HDFS-6469?focusedCommentId=14057235&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14057235].
But saying its a primary goal is not fair, you know me better than that.
Let me comment on the design. We actually looked at multiple consensus
algorithms and their implementations and came up with an abstractions that
suite the area in the most general way. Particularly, the call back from
agreement to update the application state is separated from the proposing
action is because it is more generic. With some implementations of Raft a
proposer can just wait when the agreement is made and then proceed with its
execution - synchronously. But with ZK you have to set a watcher and wait for a
callback acknowledging the event - asynchronously. So Asynchronous approach
wins as more generic.
If you take Bart we can organize pickup for participants from the near station.
Also we should have a dial up.
> Introduce Coordination Engine
> -----------------------------
>
> Key: HADOOP-10641
> URL: https://issues.apache.org/jira/browse/HADOOP-10641
> Project: Hadoop Common
> Issue Type: New Feature
> Affects Versions: 3.0.0
> Reporter: Konstantin Shvachko
> Assignee: Plamen Jeliazkov
> Attachments: HADOOP-10641.patch, HADOOP-10641.patch,
> HADOOP-10641.patch, hadoop-coordination.patch
>
>
> Coordination Engine (CE) is a system, which allows to agree on a sequence of
> events in a distributed system. In order to be reliable CE should be
> distributed by itself.
> Coordination Engine can be based on different algorithms (paxos, raft, 2PC,
> zab) and have different implementations, depending on use cases, reliability,
> availability, and performance requirements.
> CE should have a common API, so that it could serve as a pluggable component
> in different projects. The immediate beneficiaries are HDFS (HDFS-6469) and
> HBase (HBASE-10909).
> First implementation is proposed to be based on ZooKeeper.
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