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https://issues.apache.org/jira/browse/HIVE-20794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16692825#comment-16692825
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Ashutosh Bapat commented on HIVE-20794:
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Updated patch with Anishek's comment on PR.
> Use Zookeeper for metastore service discovery
> ---------------------------------------------
>
> Key: HIVE-20794
> URL: https://issues.apache.org/jira/browse/HIVE-20794
> Project: Hive
> Issue Type: Improvement
> Reporter: Ashutosh Bapat
> Assignee: Ashutosh Bapat
> Priority: Major
> Labels: pull-request-available
> Attachments: HIVE-20794.01, HIVE-20794.02, HIVE-20794.03
>
>
> Right now, multiple metastore services can be specified in
> hive.metastore.uris configuration, but that list is static and can not be
> modified dynamically. Use Zookeeper for dynamic service discovery of
> metastore.
> h3. Improve ZooKeeperHiveHelper class (suggestions for name welcome)
> The Zookeeper related code (for service discovery) accesses Zookeeper
> parameters directly from HiveConf. The class is changed so that it could be
> used for both HiveServer2 and Metastore server and works with both the
> configurations. Following methods from HiveServer2 are now moved into
> ZooKeeperHiveHelper. # startZookeeperClient # addServerInstanceToZooKeeper #
> removeServerInstanceFromZooKeeper
> h3. HiveMetaStore conf changes
> # THRIFT_URIS (hive.metastore.uris) can also be used to specify ZooKeeper
> quorum. When THRIFT_SERVICE_DISCOVERY_MODE
> (hive.metastore.service.discovery.mode) is set to "zookeeper" the URIs are
> used as ZooKeeper quorum. When it's set to be empty, the URIs are used to
> locate the metastore directly.
> # Here's list of Hiveserver2's parameters and their proposed metastore conf
> counterparts. It looks odd that the Metastore related configurations do not
> have their macros start with METASTORE, but start with THRIFT. I have just
> followed naming convention used for other parameters.
> #* HIVE_SERVER2_ZOOKEEPER_NAMESPACE - THRIFT_ZOOKEEPER_NAMESPACE
> (hive.metastore.zookeeper.namespace)
> #* HIVE_ZOOKEEPER_CLIENT_PORT - THRIFT_ZOOKEEPER_CLIENT_PORT
> (hive.metastore.zookeeper.client.port)
> #* HIVE_ZOOKEEPER_CONNECTION_TIMEOUT - THRIFT_ZOOKEEPER_CONNECTION_TIMEOUT -
> (hive.metastore.zookeeper.connection.timeout)
> #* HIVE_ZOOKEEPER_CONNECTION_MAX_RETRIES -
> THRIFT_ZOOKEEPER_CONNECTION_MAX_RETRIES
> (hive.metastore.zookeeper.connection.max.retries)
> #* HIVE_ZOOKEEPER_CONNECTION_BASESLEEPTIME -
> THRIFT_ZOOKEEPER_CONNECTION_BASESLEEPTIME
> (hive.metastore.zookeeper.connection.basesleeptime)
> Following Hive ZK configurations seem to be related to managing locks and
> seem irrelevant for MS ZK.
> # HIVE_ZOOKEEPER_SESSION_TIMEOUT
> # HIVE_ZOOKEEPER_CLEAN_EXTRA_NODES
> Since there is no configuration to be published,
> HIVE_ZOOKEEPER_PUBLISH_CONFIGS does not have a THRIFT counterpart.
> h3. HiveMetaStore class changes
> # startMetaStore should also register the instance with Zookeeper, when
> configured.
> # When shutting a metastore server down it should deregister itself from
> Zookeeper, when configured.
> # These changes use the refactored code described above.
> h3. HiveMetaStoreClient class changes
> When service discovery mode is zookeeper, we fetch the metatstore URIs from
> the specified ZooKeeper and treat those as if they were specified in
> THRIFT_URIS i.e. use the existing mechanisms to choose a metastore server to
> connect to and establish a connection.
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