[
https://issues.apache.org/jira/browse/HDFS-3077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13230634#comment-13230634
]
Todd Lipcon commented on HDFS-3077:
-----------------------------------
bq. The daemons can stop accepting writes when it realizes that active lock is
no longer held by the writer. Clearly an advantage of an active daemon compared
to using passive storage.
Relying on ZK here is insufficient - the actual protocol itself needs fencing
to guarantee that a quorum of loggers have seen the "lost lock" before the new
writer starts writing.
I agree with your later comments that rolling the edits is a helpful construct
here, but you need to also make sure there's consensus on the "active writer"
when beginning a new log segment.
I'm about halfway done with a prototype implementation of this, I should have
something to show by middle of next week. At that point I'll also post a more
thorough explanation of the design.
> Quorum-based protocol for reading and writing edit logs
> -------------------------------------------------------
>
> Key: HDFS-3077
> URL: https://issues.apache.org/jira/browse/HDFS-3077
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: ha, name-node
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
>
> Currently, one of the weak points of the HA design is that it relies on
> shared storage such as an NFS filer for the shared edit log. One alternative
> that has been proposed is to depend on BookKeeper, a ZooKeeper subproject
> which provides a highly available replicated edit log on commodity hardware.
> This JIRA is to implement another alternative, based on a quorum commit
> protocol, integrated more tightly in HDFS and with the requirements driven
> only by HDFS's needs rather than more generic use cases. More details to
> follow.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
