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https://issues.apache.org/jira/browse/HDFS-3077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13418763#comment-13418763
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Aaron T. Myers commented on HDFS-3077:
--------------------------------------
The latest patch looks good to me. Just a few small nits. +1 to commit to a
branch once these are addressed. Please also file follow-up JIRAs for the TODOs
that are deliberately being left in this patch.
# Style nit - there are a few places where you unnecessarily put method
arguments on separate lines, even if the line isn't approaching 80 chars, e.g.:
{code}
+ public GetEditLogManifestResponseProto call() throws IOException {
+ return getProxy().getEditLogManifest(
+ journalId,
+ fromTxnId);
+ }
{code}
# Instead of System#nanoTime you should use Time#monotonicNow.
# s/Journal service/Journal Node/g: "This class is used by the lagging Journal
service to retrieve edit file from another Journal service for sync up."
# Some odd formatting:
{code}
+ response
+ .sendError(HttpServletResponse.SC_FORBIDDEN,
+ "Only Namenode and another Journal service may access this
servlet");
{code}
> 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
> Attachments: hdfs-3077-partial.txt, hdfs-3077.txt, hdfs-3077.txt,
> hdfs-3077.txt, hdfs-3077.txt, hdfs-3077.txt, hdfs-3077.txt,
> qjournal-design.pdf, qjournal-design.pdf
>
>
> 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.
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