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https://issues.apache.org/jira/browse/HBASE-18775?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16176979#comment-16176979
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stack commented on HBASE-18775:
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[~ashish singhi] I think in this case, given read-only has provenance already
in core (though it lapsed and not used that I know of), then I think it
appropriate that [~zyork] carry the read-only through to the finish.
I like the way you suggest CP to veneer a cluster w/ a single attribute; it
would be appropriate for the case where you do not have access to internals or
you want to apply the veneer atop a release w/o requiring a new version. In
this case, read-only has provenance in core (though it lapsed and not used that
I know of), so I think it appropriate that [~zyork] carry the read-only through
to the finish.
On ZK, you are correct. We want to institute a tendency where we do less ZK
with time so I'd be in favor of NOT putting a readonly notification up in zk.
We've been lazy treating zk as though it were a magic store beyond the laws of
the real world. We store all kinds of crud in there (even though hbase is a
'datastore'!). We are now safely into the realm of zk abuse. We have clients
got there to pickup cluster location -- fine -- but also state of a table
(enabled/disabled?) and we are also using it as a means for distributed
messaging; i.e. we go to a third-party system when we want to tell ourself
something even though all processes have well-established connections up and
running. We used to have a dictum that ZK be used to store transitory data
only, that you could wipe ZK and hbase would keep going, but replication at
least is in violation here. We were also using it to save intermediate
assignment state but going via a third-party system put holes in our being able
to do atomic transitions and in assignment throughput.
> Add a Global Read-Only property to turn off all writes for the cluster
> ----------------------------------------------------------------------
>
> Key: HBASE-18775
> URL: https://issues.apache.org/jira/browse/HBASE-18775
> Project: HBase
> Issue Type: Sub-task
> Components: master, regionserver
> Affects Versions: HBASE-18477
> Reporter: Zach York
> Assignee: Zach York
> Attachments: HBASE-18775.HBASE-18477.001.patch,
> HBASE-18775.HBASE-18477.002.patch, HBASE-18775.HBASE-18477.003.patch,
> HBASE-18775.HBASE-18477.004.patch
>
>
> As part of HBASE-18477, we need a way to turn off all modification for a
> cluster. This patch extends the read only mode used by replication to disable
> all data and metadata operations.
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