OceanBase CDC Connector¶

The OceanBase CDC connector allows for reading snapshot data and incremental data from OceanBase. This document describes how to setup the OceanBase CDC connector to run SQL queries against OceanBase.

Dependencies¶

In order to setup the OceanBase CDC connector, the following table provides dependency information for both projects using a build automation tool (such as Maven or SBT) and SQL Client with SQL JAR bundles.

<dependency>
  <groupId>com.ververica</groupId>
  <artifactId>flink-connector-oceanbase-cdc</artifactId>
  <!-- The dependency is available only for stable releases, SNAPSHOT dependency need build by yourself. -->
  <version>2.3.0</version>
</dependency>

SQL Client JAR¶

Download link is available only for stable releases.

Download flink-sql-connector-oceanbase-cdc-2.3.0.jar and put it under <FLINK_HOME>/lib/.

Note: flink-sql-connector-oceanbase-cdc-XXX-SNAPSHOT version is the code corresponding to the development branch. Users need to download the source code and compile the corresponding jar. Users should use the released version, such as flink-sql-connector-oceanbase-cdc-2.3.0.jar, the released version will be available in the Maven central warehouse.

Setup OceanBase and LogProxy Server¶

Setup the OceanBase cluster following the deployment doc.

Create a user with password in sys tenant, this user is used in OceanBase LogProxy. See user management doc.

mysql -h${host} -P${port} -uroot

mysql> SHOW TENANT;
mysql> CREATE USER ${sys_username} IDENTIFIED BY '${sys_password}';
mysql> GRANT ALL PRIVILEGES ON *.* TO ${sys_username} WITH GRANT OPTION;

Create a user in the tenant you want to monitor, this is used to read data for snapshot and change event.
For users of OceanBase Community Edition, you need to get the rootserver-list. You can use the following command to get the value:
```
mysql> show parameters like 'rootservice_list';
```
For users of OceanBase Enterprise Edition, you need to get the config-url. You can use the following command to get the value:
```
mysql> show parameters like 'obconfig_url';
```
Setup OceanBase LogProxy. For users of OceanBase Community Edition, you can follow the quick start.

How to create a OceanBase CDC table¶

The OceanBase CDC table can be defined as following:

-- checkpoint every 3000 milliseconds                       
Flink SQL> SET 'execution.checkpointing.interval' = '3s';

-- register a OceanBase table 'orders' in Flink SQL
Flink SQL> CREATE TABLE orders (
    order_id     INT,
    order_date   TIMESTAMP(0),
    customer_name STRING,
    price        DECIMAL(10, 5),
    product_id   INT,
    order_status BOOLEAN,
    PRIMARY KEY (order_id) NOT ENFORCED
) WITH (
    'connector' = 'oceanbase-cdc',
    'scan.startup.mode' = 'initial',
    'username' = 'user@test_tenant',
    'password' = 'pswd',
    'tenant-name' = 'test_tenant',
    'database-name' = 'test_db',
    'table-name' = 'orders',
    'hostname' = '127.0.0.1',
    'port' = '2881',
    'rootserver-list' = '127.0.0.1:2882:2881',
    'logproxy.host' = '127.0.0.1',
    'logproxy.port' = '2983',
    'working-mode' = 'memory'
);

-- read snapshot and binlogs from orders table
Flink SQL> SELECT * FROM orders;

You can also try the quickstart tutorial that sync data from OceanBase to Elasticsearch, please refer Flink CDC Tutorial for more information.

Connector Options¶

The OceanBase CDC Connector contains some options for both sql and stream api as the following sheet.

Note: The connector supports two ways to specify the table list to listen to, and will get the union of the results when both way are used at the same time.

Use database-name and table-name to match database and table names in regex. As the obcdc (former liboblog) only supports fnmatch now, we can’t use regex directly to filter change events, so these two options can only be used in initial startup mode.
Use table-list to match the exact value of database and table names.

    
        
                Option
                Required
                Default
                Type
                Description
            

        
                connector
                required
                (none)
                String
                Specify what connector to use, here should be 'oceanbase-cdc'.
            

                scan.startup.mode
                required
                (none)
                String
                Specify the startup mode for OceanBase CDC consumer, valid enumerations are
                    'initial','latest-offset' or 'timestamp'.
                
            

                scan.startup.timestamp
                optional
                (none)
                Long
                Timestamp in seconds of the start point, only used for 'timestamp' startup mode.
            

                username
                required
                (none)
                String
                Username to be used when connecting to OceanBase.
            

                password
                required
                (none)
                String
                Password to be used when connecting to OceanBase.
            

                tenant-name
                required
                (none)
                String
                Tenant name of OceanBase to monitor, should be exact value.
            

                database-name
                optional
                (none)
                String
                Database name of OceanBase to monitor, should be regular expression. Only can be used with 'initial' mode.
            

                table-name
                optional
                (none)
                String
                Table name of OceanBase to monitor, should be regular expression. Only can be used with 'initial' mode.
            

                table-list
                optional
                (none)
                String
                List of full names of tables, separated by commas, e.g. "db1.table1, db2.table2".
            

                hostname
                optional
                (none)
                String
                IP address or hostname of the OceanBase database server or OceanBase Proxy server.
            

                port
                optional
                (none)
                Integer
                Integer port number to connect to OceanBase. It can be the SQL port of OceanBase server, which is 2881 by default, or the port of OceanBase proxy service, which is 2883 by default.
            

                connect.timeout
                optional
                30s
                Duration
                The maximum time that the connector should wait after trying to connect to the OceanBase database server before timing out.
            

                server-time-zone
                optional
                +00:00
                String
                The session timezone which controls how temporal types are converted to STRING in OceanBase. Can be UTC offset in format "±hh:mm", or named time zones if the time zone information tables in the mysql database have been created and populated.
            

                logproxy.host
                required
                (none)
                String
                Hostname or IP address of OceanBase log proxy service.
            

                logproxy.port
                required
                (none)
                Integer
                Port number of OceanBase log proxy service.
            

                logproxy.client.id
                optional
                By rule.
                String
                Id of a log proxy client connection, will be in format {flink_ip}_{process_id}_{timestamp}_{thread_id}_{tenant} by default.
            

                rootserver-list
                optional
                (none)
                String
                The semicolon-separated list of OceanBase root servers in format `ip:rpc_port:sql_port`, required for OceanBase CE.
            

                config-url
                optional
                (none)
                String
                The url to get the server info from the config server, required for OceanBase EE.
            

                working-mode
                optional
                storage
                String
                Working mode of `obcdc` in LogProxy, can be `storage` or `memory`.
            

    

Available Metadata¶

The following format metadata can be exposed as read-only (VIRTUAL) columns in a table definition.

Key	DataType	Description
tenant_name	STRING NOT NULL	Name of the tenant that contains the row.
database_name	STRING NOT NULL	Name of the database that contains the row.
table_name	STRING NOT NULL	Name of the table that contains the row.
op_ts	TIMESTAMP_LTZ(3) NOT NULL	It indicates the time that the change was made in the database. If the record is read from snapshot of the table instead of the change stream, the value is always 0.

The extended CREATE TABLE example demonstrates the syntax for exposing these metadata fields:

CREATE TABLE products (
    tenant_name STRING METADATA FROM 'tenant_name' VIRTUAL,
    db_name STRING METADATA FROM 'database_name' VIRTUAL,
    table_name STRING METADATA  FROM 'table_name' VIRTUAL,
    operation_ts TIMESTAMP_LTZ(3) METADATA FROM 'op_ts' VIRTUAL,
    order_id INT,
    order_date TIMESTAMP(0),
    customer_name STRING,
    price DECIMAL(10, 5),
    product_id INT,
    order_status BOOLEAN,
    PRIMARY KEY(order_id) NOT ENFORCED
) WITH (
   'connector' = 'oceanbase-cdc',
   'scan.startup.mode' = 'initial',
   'username' = 'user@test_tenant',
   'password' = 'pswd',
   'tenant-name' = 'test_tenant',
   'database-name' = 'test_db',
   'table-name' = 'orders',
   'hostname' = '127.0.0.1',
   'port' = '2881',
   'rootserver-list' = '127.0.0.1:2882:2881',
   'logproxy.host' = '127.0.0.1',
   'logproxy.port' = '2983',
   'working-mode' = 'memory'
);

Features¶

At-Least-Once Processing¶

The OceanBase CDC connector is a Flink Source connector which will read database snapshot first and then continues to read change events with at-least-once processing.

OceanBase is a kind of distributed database whose log files are distributed on different servers. As there is no position information like MySQL binlog offset, we can only use timestamp as the position mark. In order to ensure the completeness of reading data, liboblog (a C++ library to read OceanBase log record) might read some log data before the given timestamp. So in this way we may read duplicate data whose timestamp is around the start point, and only ‘at-least-once’ can be guaranteed.

Startup Reading Position¶

The config option scan.startup.mode specifies the startup mode for OceanBase CDC consumer. The valid enumerations are:

initial: Performs an initial snapshot on the monitored table upon first startup, and continue to read the latest commit log.
latest-offset: Never to perform snapshot on the monitored table upon first startup and just read the latest commit log since the connector is started.
timestamp: Never to perform snapshot on the monitored table upon first startup and just read the commit log from the given scan.startup.timestamp.

Consume Commit Log¶

The OceanBase CDC Connector using oblogclient to consume commit log from OceanBase LogProxy.

DataStream Source¶

The OceanBase CDC connector can also be a DataStream source. You can create a SourceFunction as the following shows:

import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.source.SourceFunction;
import org.apache.flink.table.api.DataTypes;
import org.apache.flink.table.catalog.Column;
import org.apache.flink.table.catalog.ResolvedSchema;
import org.apache.flink.table.catalog.UniqueConstraint;
import org.apache.flink.table.data.RowData;
import org.apache.flink.table.runtime.typeutils.InternalTypeInfo;
import org.apache.flink.table.types.logical.RowType;

import com.ververica.cdc.connectors.oceanbase.OceanBaseSource;
import com.ververica.cdc.connectors.oceanbase.source.RowDataOceanBaseDeserializationSchema;
import com.ververica.cdc.connectors.oceanbase.table.OceanBaseDeserializationSchema;
import com.ververica.cdc.connectors.oceanbase.table.StartupMode;

import java.time.ZoneId;
import java.util.Arrays;
import java.util.Collections;

public class OceanBaseSourceExample {
   public static void main(String[] args) throws Exception {
      ResolvedSchema resolvedSchema =
              new ResolvedSchema(
                      Arrays.asList(
                              Column.physical("id", DataTypes.INT().notNull()),
                              Column.physical("name", DataTypes.STRING().notNull())),
                      Collections.emptyList(),
                      UniqueConstraint.primaryKey("pk", Collections.singletonList("id")));

      RowType physicalDataType =
              (RowType) resolvedSchema.toPhysicalRowDataType().getLogicalType();
      TypeInformation<RowData> resultTypeInfo = InternalTypeInfo.of(physicalDataType);
      String serverTimeZone = "+00:00";

      OceanBaseDeserializationSchema<RowData> deserializer =
              RowDataOceanBaseDeserializationSchema.newBuilder()
                      .setPhysicalRowType(physicalDataType)
                      .setResultTypeInfo(resultTypeInfo)
                      .setServerTimeZone(ZoneId.of(serverTimeZone))
                      .build();

      SourceFunction<RowData> oceanBaseSource =
              OceanBaseSource.<RowData>builder()
                      .rsList("127.0.0.1:2882:2881")
                      .startupMode(StartupMode.INITIAL)
                      .username("user@test_tenant")
                      .password("pswd")
                      .tenantName("test_tenant")
                      .databaseName("test_db")
                      .tableName("test_table")
                      .hostname("127.0.0.1")
                      .port(2881)
                      .logProxyHost("127.0.0.1")
                      .logProxyPort(2983)
                      .serverTimeZone(serverTimezone)
                      .deserializer(deserializer)
                      .build();

      StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

      // enable checkpoint
      env.enableCheckpointing(3000);

      env.addSource(oceanBaseSource).print().setParallelism(1);
      env.execute("Print OceanBase Snapshot + Change Events");
   }
}

Data Type Mapping¶

OceanBase type	Flink SQL type	NOTE
BOOLEAN TINYINT(1) BIT(1)	BOOLEAN
TINYINT	TINYINT
SMALLINT TINYINT UNSIGNED	SMALLINT
INT MEDIUMINT SMALLINT UNSIGNED	INT
BIGINT INT UNSIGNED	BIGINT
BIGINT UNSIGNED	DECIMAL(20, 0)
REAL FLOAT	FLOAT
DOUBLE	DOUBLE
NUMERIC(p, s) DECIMAL(p, s) where p <= 38	DECIMAL(p, s)
NUMERIC(p, s) DECIMAL(p, s) where 38 < p <=65	STRING	DECIMAL is equivalent to NUMERIC. The precision for DECIMAL data type is up to 65 in OceanBase, but the precision for DECIMAL is limited to 38 in Flink. So if you define a decimal column whose precision is greater than 38, you should map it to STRING to avoid precision loss.
DATE	DATE
TIME [(p)]	TIME [(p)]
DATETIME [(p)]	TIMESTAMP [(p)]
TIMESTAMP [(p)]	TIMESTAMP_LTZ [(p)]
CHAR(n)	CHAR(n)
VARCHAR(n)	VARCHAR(n)
BIT(n)	BINARY(⌈n/8⌉)
BINARY(n)	BINARY(n)
VARBINARY(N)	VARBINARY(N)
TINYTEXT TEXT MEDIUMTEXT LONGTEXT	STRING
TINYBLOB BLOB MEDIUMBLOB LONGBLOB	BYTES
YEAR	INT
ENUM	STRING
SET	ARRAY<STRING>	As the SET data type in OceanBase is a string object that can have zero or more values, it should always be mapped to an array of string
JSON	STRING	The JSON data type will be converted into STRING with JSON format in Flink.