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https://issues.apache.org/jira/browse/HBASE-29083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17926617#comment-17926617
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Andor Molnar commented on HBASE-29083:
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{quote}The file based register sounds like a good idea. Maybe client writes
could rely on this file too to figure the current active cluster. Have you guys
already planned how would the failover be implemented? Maybe some builtin
command that flips the config value in each cluster, then also update this file
with the new active cluster?
{quote}
[~anuj.sharma] is working on adding implementation details and ideas to the
design doc to share with the community.
The HBase filesystem is common between clusters, so certainly we can share this
information in a dedicated file, but I don't think clusters can monitor it
without significant overhead. ZooKeeper is more capable for doing that with
Watchers, but ZK ensembles are different for clusters since metadata should not
be shared. We're not planning to introduce a shared ZK cluster just for this
reason.
So we might able to do this as a new HBase operation:
* flip write -> read_only: delete "active_cluster_id" file from HBase
filesystem (verify that we're the owner) and add read_only flag to ZK znode
which is watched by all region servers,
* flip read_only -> write: add "active_cluster_id" file to HBase filesystem if
missing and remove read_only flag from watched ZK node.
> Add global read-only mode to HBase
> ----------------------------------
>
> Key: HBASE-29083
> URL: https://issues.apache.org/jira/browse/HBASE-29083
> Project: HBase
> Issue Type: Sub-task
> Components: master
> Reporter: Andor Molnar
> Assignee: Anuj Sharma
> Priority: Major
>
> Implement *read-only* mode for HBase. Can be set at the start of the cluster
> or rolling restart.
> New config setting:
> |*Config*|*Default* |*Explanation*|
> |hbase.global.readonly.enabled|false|Puts the entire cluster into read-only
> mode.|
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