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https://issues.apache.org/jira/browse/HBASE-18095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17117912#comment-17117912
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Nick Dimiduk commented on HBASE-18095:
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We have dynamic reloading of configuration implemented in some areas. The
ability to reload the configured master addresses seems like a good place to
make use of that capability.
As for extending the interface, that would be fine, if a little heavy-handed. I
prefer it be a separate interface, as you suggest, so that it can be swapped
out without having to re-implement the entire registry. For the interface
itself, should it return a {{Set}} of {{java.net.URL}} or
{{java.net.SocketAddress}} instead?
> Provide an option for clients to find the server hosting META that does not
> involve the ZooKeeper client
> --------------------------------------------------------------------------------------------------------
>
> Key: HBASE-18095
> URL: https://issues.apache.org/jira/browse/HBASE-18095
> Project: HBase
> Issue Type: New Feature
> Components: Client
> Reporter: Andrew Kyle Purtell
> Assignee: Bharath Vissapragada
> Priority: Major
> Fix For: 3.0.0-alpha-1, 2.3.0
>
> Attachments: HBASE-18095.master-v1.patch, HBASE-18095.master-v2.patch
>
>
> Clients are required to connect to ZooKeeper to find the location of the
> regionserver hosting the meta table region. Site configuration provides the
> client a list of ZK quorum peers and the client uses an embedded ZK client to
> query meta location. Timeouts and retry behavior of this embedded ZK client
> are managed orthogonally to HBase layer settings and in some cases the ZK
> cannot manage what in theory the HBase client can, i.e. fail fast upon outage
> or network partition.
> We should consider new configuration settings that provide a list of
> well-known master and backup master locations, and with this information the
> client can contact any of the master processes directly. Any master in either
> active or passive state will track meta location and respond to requests for
> it with its cached last known location. If this location is stale, the client
> can ask again with a flag set that requests the master refresh its location
> cache and return the up-to-date location. Every client interaction with the
> cluster thus uses only HBase RPC as transport, with appropriate settings
> applied to the connection. The configuration toggle that enables this
> alternative meta location lookup should be false by default.
> This removes the requirement that HBase clients embed the ZK client and
> contact the ZK service directly at the beginning of the connection lifecycle.
> This has several benefits. ZK service need not be exposed to clients, and
> their potential abuse, yet no benefit ZK provides the HBase server cluster is
> compromised. Normalizing HBase client and ZK client timeout settings and
> retry behavior - in some cases, impossible, i.e. for fail-fast - is no longer
> necessary.
> And, from [~ghelmling]: There is an additional complication here for
> token-based authentication. When a delegation token is used for SASL
> authentication, the client uses the cluster ID obtained from Zookeeper to
> select the token identifier to use. So there would also need to be some
> Zookeeper-less, unauthenticated way to obtain the cluster ID as well.
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