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https://issues.apache.org/jira/browse/HBASE-10070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13875492#comment-13875492
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stack commented on HBASE-10070:
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You may not have seen my response above where I think we should not talk of
replicas in our model all. We should call the region instances something else
and then in a layer above do designations such as "primary" or "leader" and
"read-only replica" or "follower". If you agree with me, the 'desired region
model' you propose in your comment is no longer appropriate.
Sorry Enis, I don't get your second paragraph above. Pardon me. It is a
failing on my part. I'm having trouble untangling what the 'Right now' refers
to, whether it is trunk or your work on this feature so far.... and what
'whether this is possible' refers to.
bq. I guess we can add it there, but add special case handling for parsing
back. Would that work?
I haven't done the research but am thinking that a wholesale move to a new
region naming scheme for all new region creations better than a scheme where we
have 'replicas' named with one format and everything else another.
> HBase read high-availability using eventually consistent region replicas
> ------------------------------------------------------------------------
>
> Key: HBASE-10070
> URL: https://issues.apache.org/jira/browse/HBASE-10070
> Project: HBase
> Issue Type: New Feature
> Reporter: Enis Soztutar
> Assignee: Enis Soztutar
> Attachments: HighAvailabilityDesignforreadsApachedoc.pdf
>
>
> In the present HBase architecture, it is hard, probably impossible, to
> satisfy constraints like 99th percentile of the reads will be served under 10
> ms. One of the major factors that affects this is the MTTR for regions. There
> are three phases in the MTTR process - detection, assignment, and recovery.
> Of these, the detection is usually the longest and is presently in the order
> of 20-30 seconds. During this time, the clients would not be able to read the
> region data.
> However, some clients will be better served if regions will be available for
> reads during recovery for doing eventually consistent reads. This will help
> with satisfying low latency guarantees for some class of applications which
> can work with stale reads.
> For improving read availability, we propose a replicated read-only region
> serving design, also referred as secondary regions, or region shadows.
> Extending current model of a region being opened for reads and writes in a
> single region server, the region will be also opened for reading in region
> servers. The region server which hosts the region for reads and writes (as in
> current case) will be declared as PRIMARY, while 0 or more region servers
> might be hosting the region as SECONDARY. There may be more than one
> secondary (replica count > 2).
> Will attach a design doc shortly which contains most of the details and some
> thoughts about development approaches. Reviews are more than welcome.
> We also have a proof of concept patch, which includes the master and regions
> server side of changes. Client side changes will be coming soon as well.
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