Hive/Impala replication policy concepts

Hive/Impala replication enables you to copy (replicate) your Hive metastore and data from one cluster to another and synchronize the Hive metastore and data set on the destination cluster with the source, based on a specified replication policy.

Minimum Required Role: Replication Administrator (also provided by Full Administrator)

The destination cluster must be managed by the Cloudera Manager Server where the replication is being set up, and the source cluster can be managed by that same server or by a peer Cloudera Manager Server.

note

Because of the warehouse directory changes between CDH clusters and CDP-DC, Hive replication does not copy the table data from the database and tables specified in the source cluster. But the replication job gets successfully run without any disruptions. While replicating from CDH clusters to CDP-DC, it is recommended that the HDFS Destination Path is defined. If HDFS Destination Path is not defined and Replicate HDFS File is set as true, the data is replicated with the original source name. For example, the replicated table data was to reside under /warehouse/tablespace/external/hive directory but the data was replicated to /user/hive/warehouse location. Also, not defining HDFS Destination Path before the replication process can result in a large chunk of HDFS space being used for unwanted data movement.

important

Since Hive3 has a different default table type and warehouse directory structure, the following changes apply while replicating Hive data from CDH5 or CDH6 versions to CDP-DC:

All tables become External tables during Hive replication. This is because the default table type is ACID in Hive3, which is the only managed table type. As of this release, BDR does not support Hive2 -> Hive3 replication into ACID tables and all the tables are necessarily replicated as External tables.
Replicated tables will be created under external Hive warehouse directory set by hive.metastore.warehouse.external.dir Hive configuration parameter. Users have to make sure that this has a different value than hive.metastore.warehouse.dir Hive configuration parameter, that is the location of Managed tables.
If users want to replicate the same database from Hive2 to Hive3 (that will have different paths by design), they need to use Force Overwrite option per policy to avoid any mismatch issues.

Configuration notes:

If the hadoop.proxyuser.hive.groups configuration has been changed to restrict access to the Hive Metastore Server to certain users or groups, the hdfs group or a group containing the hdfs user must also be included in the list of groups specified for Hive/Impala replication to work. This configuration can be specified either on the Hive service as an override, or in the core-site HDFS configuration. This applies to configuration settings on both the source and destination clusters.
If you configured on the target cluster for the directory where HDFS data is copied during Hive/Impala replication, the permissions that were copied during replication, are overwritten by the HDFS ACL synchronization and are not preserved.