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https://issues.apache.org/jira/browse/HBASE-10070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13873009#comment-13873009
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Enis Soztutar commented on HBASE-10070:
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bq. What delivery timeline are we talking? Is this is for 1.0 hbase? Or is it
post 1.0? If the later, maybe we want to go more radical than what is being
proposed here.
Forgot to answer that earlier. I think it will depend on the timing of 1.0 vs
timing of this branch. I think we can get all of the patches (for phase 1) in a
mature and reviewed state in 1-2 months. Then at the time of the merge
proposal, we can see how far along we are at the 1.0 release candidate. AFAIK,
current trunk does not contain anything that is not there in 0.98, so we that
means whether we should go with 1.0 = a mature version of 0.98 approach or 1.0
= mature version of 0.99 approach. I prefer the latter, but that is up for
discussion in the mailing list I guess.
> 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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