MySQL CDC

MySQL CDC source connector

Description​

The MySQL CDC connector allows for reading snapshot data and incremental data from MySQL database. This document describes how to set up the MySQL CDC connector to run SQL queries against MySQL databases.

Key features​

• batch

• stream

• exactly-once

• column projection

• parallelism

• support user-defined split

Creating MySQL user​

You have to define a MySQL user with appropriate permissions on all databases that the Debezium MySQL connector monitors.

1. Create the MySQL user:

mysql> CREATE USER 'user'@'localhost' IDENTIFIED BY 'password';

1. Grant the required permissions to the user:

mysql> GRANT SELECT, RELOAD, SHOW DATABASES, REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'user' IDENTIFIED BY 'password';

1. Finalize the user’s permissions:

mysql> FLUSH PRIVILEGES;

Enabling the MySQL Binlog​

You must enable binary logging for MySQL replication. The binary logs record transaction updates for replication tools to propagate changes.

1. Check whether the log-bin option is already on:

mysql> show variables where variable_name in ('log_bin', 'binlog_format', 'binlog_row_image', 'gtid_mode', 'enforce_gtid_consistency');
+--------------------------+----------------+
| Variable_name            | Value          |
+--------------------------+----------------+
| binlog_format            | ROW            |
| binlog_row_image         | FULL           |
| enforce_gtid_consistency | ON             |
| gtid_mode                | ON             |
| log_bin                  | ON             |
+--------------------------+----------------+
5 rows in set (0.00 sec)

1. If inconsistent with the above results, configure your MySQL server configuration file($MYSQL_HOME/mysql.cnf) with the following properties, which are described in the table below:

# Enable binary replication log and set the prefix, expiration, and log format.
# The prefix is arbitrary, expiration can be short for integration tests but would
# be longer on a production system. Row-level info is required for ingest to work.
# Server ID is required, but this will vary on production systems
server-id         = 223344
log_bin           = mysql-bin
expire_logs_days  = 10
binlog_format     = row
# mysql 5.6+ requires binlog_row_image to be set to FULL
binlog_row_image  = FULL

# enable gtid mode
# mysql 5.6+ requires gtid_mode to be set to ON
gtid_mode = on
enforce_gtid_consistency = on

1. Restart MySQL Server

/etc/inint.d/mysqld restart

1. Confirm your changes by checking the binlog status once more:

MySQL 5.5:

mysql> show variables where variable_name in ('log_bin', 'binlog_format', 'binlog_row_image', 'gtid_mode', 'enforce_gtid_consistency');
+--------------------------+----------------+
| Variable_name            | Value          |
+--------------------------+----------------+
| binlog_format            | ROW            |
| log_bin                  | ON             |
+--------------------------+----------------+
5 rows in set (0.00 sec)

MySQL 5.6+:

mysql> show variables where variable_name in ('log_bin', 'binlog_format', 'binlog_row_image', 'gtid_mode', 'enforce_gtid_consistency');
+--------------------------+----------------+
| Variable_name            | Value          |
+--------------------------+----------------+
| binlog_format            | ROW            |
| binlog_row_image         | FULL           |
| enforce_gtid_consistency | ON             |
| gtid_mode                | ON             |
| log_bin                  | ON             |
+--------------------------+----------------+
5 rows in set (0.00 sec)

Notes​

Setting up MySQL session timeouts​

When an initial consistent snapshot is made for large databases, your established connection could timeout while the tables are being read. You can prevent this behavior by configuring interactive_timeout and wait_timeout in your MySQL configuration file.

• interactive_timeout: The number of seconds the server waits for activity on an interactive connection before closing it. See MySQL’s documentation for more details.
• wait_timeout: The number of seconds the server waits for activity on a non-interactive connection before closing it. See MySQL’s documentation for more details.

For more database settings see Debezium MySQL Connector

Data Type Mapping​

Mysql Data Type	Nexus Data Type
BIT(1) TINYINT(1)	BOOLEAN
TINYINT	TINYINT
TINYINT UNSIGNED SMALLINT	SMALLINT
SMALLINT UNSIGNED MEDIUMINT MEDIUMINT UNSIGNED INT INTEGER YEAR	INT
INT UNSIGNED INTEGER UNSIGNED BIGINT	BIGINT
BIGINT UNSIGNED	DECIMAL(20,0)
DECIMAL(p, s) DECIMAL(p, s) UNSIGNED NUMERIC(p, s) NUMERIC(p, s) UNSIGNED	DECIMAL(p,s)
FLOAT FLOAT UNSIGNED	FLOAT
DOUBLE DOUBLE UNSIGNED REAL REAL UNSIGNED	DOUBLE
CHAR VARCHAR TINYTEXT MEDIUMTEXT TEXT LONGTEXT ENUM JSON ENUM	STRING
DATE	DATE
TIME(s)	TIME(s)
DATETIME TIMESTAMP(s)	TIMESTAMP(s)
BINARY VARBINAR BIT(p) TINYBLOB MEDIUMBLOB BLOB LONGBLOB GEOMETRY	BYTES

Source Options​

Name	Type	Required	Default	Description
base-url	String	Yes	-	The URL of the JDBC connection. Refer to a case: jdbc:mysql://localhost:3306:3306/test.
username	String	Yes	-	Name of the database to use when connecting to the database server.
password	String	Yes	-	Password to use when connecting to the database server.
database-names	List	No	-	Database name of the database to monitor.
table-names	List	Yes	-	Table name of the database to monitor. The table name needs to include the database name, for example: database_name.table_name
table-names-config	List	No	-	Table config list. for example: [{"table": "db1.schema1.table1","primaryKeys":["key1"]}]
startup.mode	Enum	No	INITIAL	Optional startup mode for MySQL CDC consumer, valid enumerations are initial, earliest, latest and specific. initial: Synchronize historical data at startup, and then synchronize incremental data. earliest: Startup from the earliest offset possible. latest: Startup from the latest offset. specific: Startup from user-supplied specific offsets.
startup.specific-offset.file	String	No	-	Start from the specified binlog file name. Note, This option is required when the startup.mode option used specific.
startup.specific-offset.pos	Long	No	-	Start from the specified binlog file position. Note, This option is required when the startup.mode option used specific.
stop.mode	Enum	No	NEVER	Optional stop mode for MySQL CDC consumer, valid enumerations are never, latest or specific. never: Real-time job don't stop the source. latest: Stop from the latest offset. specific: Stop from user-supplied specific offset.
stop.specific-offset.file	String	No	-	Stop from the specified binlog file name. Note, This option is required when the stop.mode option used specific.
stop.specific-offset.pos	Long	No	-	Stop from the specified binlog file position. Note, This option is required when the stop.mode option used specific.
snapshot.split.size	Integer	No	8096	The split size (number of rows) of table snapshot, captured tables are split into multiple splits when read the snapshot of table.
snapshot.fetch.size	Integer	No	1024	The maximum fetch size for per poll when read table snapshot.
server-id	String	No	-	A numeric ID or a numeric ID range of this database client, The numeric ID syntax is like 5400, the numeric ID range syntax is like '5400-5408'. Every ID must be unique across all currently-running database processes in the MySQL cluster. This connector joins the MySQL cluster as another server (with this unique ID) so it can read the binlog. By default, a random number is generated between 6500 and 2,148,492,146, though we recommend setting an explicit value.
server-time-zone	String	No	UTC	The session time zone in database server. If not set, then ZoneId.systemDefault() is used to determine the server time zone.
connect.timeout.ms	Duration	No	30000	The maximum time that the connector should wait after trying to connect to the database server before timing out.
connect.max-retries	Integer	No	3	The max retry times that the connector should retry to build database server connection.
connection.pool.size	Integer	No	20	The jdbc connection pool size.
chunk-key.even-distribution.factor.upper-bound	Double	No	100	The upper bound of the chunk key distribution factor. This factor is used to determine whether the table data is evenly distributed. If the distribution factor is calculated to be less than or equal to this upper bound (i.e., (MAX(id) - MIN(id) + 1) / row count), the table chunks would be optimized for even distribution. Otherwise, if the distribution factor is greater, the table will be considered as unevenly distributed and the sampling-based sharding strategy will be used if the estimated shard count exceeds the value specified by sample-sharding.threshold. The default value is 100.0.
chunk-key.even-distribution.factor.lower-bound	Double	No	0.05	The lower bound of the chunk key distribution factor. This factor is used to determine whether the table data is evenly distributed. If the distribution factor is calculated to be greater than or equal to this lower bound (i.e., (MAX(id) - MIN(id) + 1) / row count), the table chunks would be optimized for even distribution. Otherwise, if the distribution factor is less, the table will be considered as unevenly distributed and the sampling-based sharding strategy will be used if the estimated shard count exceeds the value specified by sample-sharding.threshold. The default value is 0.05.
sample-sharding.threshold	Integer	No	1000	This configuration specifies the threshold of estimated shard count to trigger the sample sharding strategy. When the distribution factor is outside the bounds specified by chunk-key.even-distribution.factor.upper-bound and chunk-key.even-distribution.factor.lower-bound, and the estimated shard count (calculated as approximate row count / chunk size) exceeds this threshold, the sample sharding strategy will be used. This can help to handle large datasets more efficiently. The default value is 1000 shards.
inverse-sampling.rate	Integer	No	1000	The inverse of the sampling rate used in the sample sharding strategy. For example, if this value is set to 1000, it means a 1/1000 sampling rate is applied during the sampling process. This option provides flexibility in controlling the granularity of the sampling, thus affecting the final number of shards. It's especially useful when dealing with very large datasets where a lower sampling rate is preferred. The default value is 1000.
exactly_once	Boolean	No	false	Enable exactly once semantic.
format	Enum	No	DEFAULT	Optional output format for MySQL CDC, valid enumerations are DEFAULT、COMPATIBLE_DEBEZIUM_JSON.
debezium	Config	No	-	Pass-through Debezium's properties to Debezium Embedded Engine which is used to capture data changes from MySQL server.
common-options		no	-	Source plugin common parameters, please refer to Source Common Options for details

Task Example​

Simple​

Support multi-table reading

env {
  parallelism = 1
  job.mode = "STREAMING"
  checkpoint.interval = 10000
}

source {
  MySQL-CDC {
    base-url = "jdbc:mysql://localhost:3306/testdb"
    username = "root"
    password = "root@123"
    table-names = ["testdb.table1", "testdb.table2"]
    
    startup.mode = "initial"
  }
}

sink {
  Console {
  }
}

Support debezium-compatible format send to kafka​

Must be used with kafka connector sink, see compatible debezium format for details

Support custom primary key for table​

env {
  parallelism = 1
  job.mode = "STREAMING"
  checkpoint.interval = 10000
}

source {
  MySQL-CDC {
    base-url = "jdbc:mysql://localhost:3306/testdb"
    username = "root"
    password = "root@123"
    
    table-names = ["testdb.table1", "testdb.table2"]
    table-names-config = [
      {
        table = "testdb.table2"
        primaryKeys = ["id"]
      }
    ]
  }
}

sink {
  Console {
  }
}