You must configure Greenplum Database client host access and role privileges and attributes before using the VMware Greenplum Connector for Apache Spark to transfer data between your Greenplum Database and Spark clusters.

Once you start running Spark applications that use the Connector, you may be required to perform certain Greenplum Database maintenance tasks.

These Greenplum Database configuration and maintenance tasks, described below, must be performed by a Greenplum user with administrative (SUPERUSER) privileges unless otherwise noted.

Configuring Greenplum Database

Client Host Access

You must explicitly configure Greenplum Database to permit access from all Spark nodes and stand-alone clients. Configure access for each Spark node, Greenplum database, and Greenplum Database role combination in the pg_hba.conf file on the master node.

Refer to Configuring Client Authentication in the Greenplum Database documentation for detailed information on configuring pg_hba.conf.

Role Privileges

The Connector uses JDBC to communicate with the Greenplum Database master node. The Greenplum user/role name that you provide when you use the Connector to transfer data between Greenplum Database and Spark must have certain privileges assigned by the administrator:

  • The user/role must have SELECT permission on the following Greenplum Database catalogs:

    • information_schema.tables, pg_attribute, pg_class, pg_namespace, gp_segment_configuration, pg_stats, pg_settings, gp_distributed_xacts
    • gp_distribution_policy (Greenplum 5 only)
  • The user/role must have USAGE privilege on each non-public database schema that has tables that the user will read:

    <db-name>=# GRANT USAGE ON SCHEMA <schema_name> TO <user_name>;
  • The user/role must have CREATE privilege on each non-public database schema in which tables the user will write to reside:

    <db-name>=# GRANT CREATE ON SCHEMA <schema_name> TO <user_name>;
  • The user/role must have the SELECT privilege on every Greenplum Database table that the user will read into Spark:

    <db-name>=# GRANT SELECT ON <schema_name>.<table_name> TO <user_name>;
  • To read a Greeplum Database table into Spark, the user/role must have permission to create writable external tables using the Greenplum Database gpfdist protocol:

    <db-name>=# ALTER USER <user_name> CREATEEXTTABLE(type = 'writable', protocol = 'gpfdist');
  • If the user/role writing to Greenplum Database is not a database or table owner, the role must have SELECT and INSERT privileges on each existing Greenplum Database table to which the user will write Spark data:

    <db-name>=# GRANT SELECT, INSERT ON <schema_name>.<table_name> TO <user_name>;
  • To write Spark data into a Greeplum Database table, the user/role must have permission to create readable external tables using the Greenplum Database gpfdist protocol:

    <db-name>=# ALTER USER <user_name> CREATEEXTTABLE(type = 'readable', protocol = 'gpfdist');

See the Greenplum Database Managing Roles and Privileges documention for further information on assigning privileges to Greenplum Database users.

gpfdists TLS Configuration

TLS can only be used when running Spark jobs on a cluster deployed in Kubernetes.

You can configure the Connector to use a TLS-secured connection between Greenplum Database segments and the edge of the Kubernetes cluster as described in Configuring the Connector When Spark is Deployed in Kubernetes (Beta). When you configure the Connector to use gpfdists for Spark access in a Kubernetes cluster, the following client certificate files must reside in the $PGDATA/gpfdists directory on each Greenplum Database segment host:

  • The client certificate file, client.crt.
  • The client private key file, client.key.
  • The trusted certificate authorities, root.crt.

The Connector requires that these files be in place, regardless of the setting of the verify_gpfdist_cert Greenplum server configuration parameter.

Refer to the Greenplum Database gpfdists:// Protocol documentation for more information about configuring the client certificates.

Greenplum Database Maintenance Tasks

The Connector uses Greenplum Database external temporary tables to load data between Greenplum and Spark. Maintenance tasks when you use the Connector may include:

  • Periodically checking the status of your Greenplum Database catalogs for bloat, and VACUUM-ing the catalog as appropriate. Refer to the Greenplum Database System Catalog Maintenance and VACUUM documentation for further information.
  • Periodically ANALYZE-ing the Greenplum Database tables that applications using the Connector load into Spark. Refer to the Greenplum Database Updating Statistics with ANALYZE and ANALYZE documentation for further information.

In addition to users with Greenplum Database SUPERUSER privileges, database or table owners may perform the maintenance tasks identified above.

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