Hive external table replication policies

Hive external table replication policies enable 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. You can also use CDP Private Cloud Base Replication Manager to replicate Hive/Impala data to and from S3 or ADLS, however you cannot replicate data from one S3 or ADLS instance to another using Replication Manager.

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.

caution

Because of the warehouse directory changes between CDH clusters and CDP Private Cloud Base, Hive external table 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 Private Cloud Base, 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 Private Cloud Base:

When you replicate from a CDH cluster to a CDP Private Cloud Base cluster, all tables become External tables during Hive external table replication. This is because the default table type is ACID in Hive3, which is the only managed table type. As of this release, Replication Manager does not support Hive2 -> Hive3 replication into ACID tables and all the tables will necessarily be replicated as External tables.
note
Managed tables are not supported by Replication Manager when you replicate data between CDP Private Cloud Base clusters.
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.
note
To perform Sentry to Ranger replication using Hive external table replication policies, you must have installed Cloudera Manager version 6.3.1 and higher on the source cluster and Cloudera Manager version 7.1.1 and higher on the target cluster.

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

Hive external table replication policies do not support managed to managed table replication. When you replicate from a CDH cluster to a CDP Private Cloud Base cluster, Replication Manager converts managed tables to external tables. Therefore, to replicate managed tables (ACID) and external tables in a database successfully, you must perform the following steps in the order shown below:

Create Hive ACID table replication policy for the database to replicate the managed data.
After the replication completes, create the Hive external table replication policy to replicate the external tables in the database.

To replicate Hive/Impala data to and from S3 or ADLS, you must have the appropriate credentials to access the S3 or ADLS account. Additionally, you must create buckets in S3 or data lake store in ADLS. Replication Manager backs up file metadata, including extended attributes and ACLs when you replicate data to cloud storage. Replication Manager supports the following replication scenarios:

Replicate to and from Amazon S3 from CDH 5.14+ and Cloudera Manager version 5.13+.
Replication Manager does not support S3 as a source or destination when S3 is configured to use SSE-KMS.
Replicate to and from Microsoft ADLS Gen1 from CDH 5.13+ and Cloudera Manager 5.15, 5.16, 6.1+.
Replicate to Microsoft ADLS Gen2 (ABFS) from CDH 5.13+ and Cloudera Manager 6.1+.