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From "Gary Helmling (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18095) Provide an option for clients to find the server hosting META that does not involve the ZooKeeper client
Date Wed, 31 May 2017 00:25:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16030415#comment-16030415
] 

Gary Helmling commented on HBASE-18095:
---------------------------------------

bq. Cluster ID lookup is most easily accomplished with a new servlet on the HTTP(S) endpoint
on the masters, serving the cluster ID as plain text

Seems like the best option.  Would this still work if SPNEGO is enabled?  If not, I'm not
sure what else we can do short of a totally new endpoint.

> 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 Purtell
>
> 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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