Flink connector

Overview

The Apache Gravitino Flink connector implements the Catalog Store to manage the catalogs under Gravitino. This capability allows users to perform federation queries, accessing data from various catalogs through a unified interface and consistent access control.

The connector talks to the Gravitino server API, port 8090 by default. To reach Iceberg catalogs through the Iceberg REST service on port 9001 instead, see Flink via Iceberg REST.

The connector is published as a version-specific runtime JAR for each supported Flink minor version. Internally, Gravitino uses shared connector logic with version-specific catalog and factory entry points so that each runtime artifact matches the Flink APIs it runs against.

Capabilities

1. Supports Hive catalog
2. Supports Iceberg catalog
3. Supports Paimon catalog
4. Supports Jdbc catalog
5. Supports most DDL and DML SQLs.

Prerequisites

• Scala 2.12
• Flink 1.18, 1.19, or 1.20
• JDK 8, 11 or 17

Usage

1. Build or download the Gravitino Flink connector runtime JAR that matches your Flink minor version, and place it in the classpath of Flink.

   Flink version	Runtime artifact
   1.18	gravitino-flink-connector-runtime-1.18_2.12-${gravitino-version}.jar
   1.19	gravitino-flink-connector-runtime-1.19_2.12-${gravitino-version}.jar
   1.20	gravitino-flink-connector-runtime-1.20_2.12-${gravitino-version}.jar

   Do not mix runtime JARs from different Flink minor versions in the same Flink deployment.

2. Configure the Flink configuration to use the Gravitino flink connector.

   Property	Type	Default Value	Description	Required
   table.catalog-store.kind	string	generic_in_memory	The Catalog Store name, it should set to gravitino.	Yes
   table.catalog-store.gravitino.gravitino.metalake	string	(none)	The metalake name that flink connector used to request to Gravitino.	Yes
   table.catalog-store.gravitino.gravitino.uri	string	(none)	The uri of Gravitino server address.	Yes
   table.catalog-store.gravitino.gravitino.enableSessionCatalogSupport	boolean	false	Whether to enable support for Flink's session catalog in the Gravitino catalog store.	No
   table.catalog-store.gravitino.gravitino.client.	string	(none)	The configuration key prefix for the Gravitino client config.	No

   When table.catalog-store.gravitino.gravitino.enableSessionCatalogSupport is set to true, Gravitino uses GravitinoSessionCatalogStore, which combines a GravitinoCatalogStore (backed by the Gravitino server) with an in-memory store to support Flink's session catalog. When false (the default), only GravitinoCatalogStore is used.

   When session catalog support is enabled, the following behaviors apply:

   • CREATE CATALOG: Gravitino-managed catalogs (e.g. gravitino-hive, gravitino-iceberg) are persisted to the Gravitino server; non-Gravitino-managed catalogs (e.g. hive, jdbc, or any custom connector type) are stored in the in-memory store only.
   • GET / USE CATALOG: The in-memory store is checked first. If the catalog is not found there, it is retrieved from the Gravitino server.
   • DROP CATALOG: The in-memory store is checked first. If the catalog exists there it is removed from memory; otherwise it is removed from the Gravitino server.
   • SHOW / LIST CATALOGS: Returns the combined set of catalogs from both the in-memory store and the Gravitino server.
   • Session scope: Catalogs stored only in memory are session-scoped and will not survive when Flink restarts.
   • Name conflict: If a catalog with the same name exists in both stores, the in-memory entry takes precedence.

   To configure the Gravitino client, use properties prefixed with table.catalog-store.gravitino.gravitino.client.. These properties will be passed to the Gravitino client after removing the table.catalog-store.gravitino. prefix.

   Example: Setting table.catalog-store.gravitino.gravitino.client.socketTimeoutMs is equivalent to setting gravitino.client.socketTimeoutMs for the Gravitino client.

   Note: Invalid configuration properties will result in exceptions. Please see Gravitino Java client configurations for more support client configuration.

   Set the flink configuration in flink-conf.yaml.

   flink-conf.yaml

   table.catalog-store.kind: gravitino
   table.catalog-store.gravitino.gravitino.metalake: metalake_demo
   table.catalog-store.gravitino.gravitino.uri: http://localhost:8090
   table.catalog-store.gravitino.gravitino.enableSessionCatalogSupport: true
   table.catalog-store.gravitino.gravitino.client.socketTimeoutMs: 60000
   table.catalog-store.gravitino.gravitino.client.connectionTimeoutMs: 60000

   Or you can set the flink configuration in the TableEnvironment.

   Configure the catalog store in the TableEnvironment

   final Configuration configuration = new Configuration();
   configuration.setString("table.catalog-store.kind", "gravitino");
   configuration.setString("table.catalog-store.gravitino.gravitino.metalake", "metalake_demo");
   configuration.setString("table.catalog-store.gravitino.gravitino.uri", "http://localhost:8090");
   configuration.setBoolean("table.catalog-store.gravitino.gravitino.enableSessionCatalogSupport", true);
   configuration.setString("table.catalog-store.gravitino.gravitino.client.socketTimeoutMs", "60000");
   configuration.setString("table.catalog-store.gravitino.gravitino.client.connectionTimeoutMs", "60000");
   EnvironmentSettings.Builder builder = EnvironmentSettings.newInstance().withConfiguration(configuration);
   TableEnvironment tableEnv = TableEnvironment.create(builder.inBatchMode().build());

3. Add necessary jar files to Flink's classpath.

   To run Flink with Gravitino connector and then access the data source like Hive, you may need to put additional jars to Flink's classpath. You can refer to the Flink document for more information.

4. Execute the Flink SQL query.

   Suppose there is only one hive catalog with the name catalog_hive in the metalake metalake_demo.

   Query a Hive catalog from Flink SQL

   -- use hive catalog
   USE CATALOG catalog_hive;
   CREATE DATABASE db;
   USE db;
   SET 'execution.runtime-mode' = 'batch';
   SET 'sql-client.execution.result-mode' = 'tableau';
   CREATE TABLE hive_students (id INT, name STRING);
   INSERT INTO hive_students VALUES (1, 'Alice'), (2, 'Bob');
   SELECT * FROM hive_students;

Catalog naming restrictions

When creating catalogs that will be used with the Flink connector, the catalog name cannot start with a number. This is a Flink limitation. For example:

• ✅ Valid: catalog_hive, hive_catalog, my_catalog_1
• ❌ Invalid: 1_catalog, 123catalog, 2hive

If you create a catalog with a name starting with a number, it will not be accessible from Flink.

Datatype mapping

Gravitino flink connector support the following datatype mapping between Flink and Gravitino.

Flink Type	Gravitino Type
array	list
bigint	long
binary	fixed
boolean	boolean
char	char
date	date
decimal	decimal
double	double
float	float
integer	integer
map	map
null	null
row	struct
smallint	short
time	time
timestamp	timestamp without time zone
timestamp without time zone	timestamp without time zone
timestamp with time zone	timestamp with time zone
timestamp with local time zone	timestamp with time zone
timestamp_ltz	timestamp with time zone
tinyint	byte
varbinary	binary
varchar	string