Updated on 2024-04-11 GMT+08:00

From MySQL to Kafka

Supported Source and Destination Databases

Table 1 Supported databases

Source DB

Destination DB

  • On-premises MySQL databases
  • MySQL databases on an ECS
  • Kafka

Prerequisites

  • You have logged in to the DRS console.
  • For details about the DB types and versions supported by real-time synchronization, see Real-Time Synchronization.

Suggestions

  • When a task is being started or in the full synchronization phase, do not perform DDL operations on the source database. Otherwise, the task may be abnormal.
  • To keep data consistency before and after the synchronization, ensure that no data is written to the destination database during the synchronization.
  • The success of database synchronization depends on environment and manual operations. To ensure a smooth synchronization, perform a synchronization trial before you start the synchronization to help you detect and resolve problems in advance.
  • It is recommended that you start a task during off-peak hours to minimize the impact of synchronization on your services.
    • If network bandwidth is not limited, the query rate of the source database increases by about 50 MB/s during full synchronization, and two to four CPUs are occupied.
    • Tables to be synchronized without a primary key may be locked for 3s.
    • When DRS concurrently reads data from a database, it will use about 6 to 10 sessions. The impact of the connections on services must be considered.
    • If you read a table, especially a large table, during the full synchronization, the exclusive lock on that table may be blocked.

Precautions

Before creating a synchronization task, read the following notes:

  • You are advised to create an independent database account for DRS task connection to prevent task failures caused by database account password modification.
  • After changing the account passwords for the source or destination databases, modify the connection information in the DRS task as soon as possible to prevent automatic retry after a task failure. Automatic retry will lock the database accounts.
Table 2 Precautions

Type

Restrictions

Database permissions

  • The source database user must have the following permissions: SELECT, LOCK TABLES, SHOW VIEW, EVENT, REPLICATION SLAVE, and REPLICATION CLIENT.

Synchronization object

  • During full synchronization, tables, primary key indexes, unique indexes, common indexes, stored procedures, views, and functions can be synchronized, but events and triggers cannot be synchronized. During incremental synchronization, only table data and DDLs can be synchronized.
  • Tables with storage engine different to MyISAM and InnoDB cannot be synchronized.

Source database

  • During the incremental synchronization, the binlog of the source MySQL database must be enabled and use the row-based format.
  • If the storage space is sufficient, store the source database binlog for as long as possible. The recommended retention period is three days. If this period is set to 0, the synchronization may fail.
    • If the source database is an on-premises MySQL database, set expire_logs_days to specify the binlog retention period. Set expire_logs_day to a proper value to ensure that the binlog does not expire before data transfer resumes. This ensures that services can be recovered after interruption.
    • If the source database is an RDS for MySQL instance, set the binlog retention period by following the instructions provided in RDS User Guide.
  • GTID must be enabled for the source database. If GTID is not enabled for the source database, primary/standby switchover is not supported. DRS tasks will be interrupted and cannot be restored during a switchover.
  • During an incremental synchronization, the server_id value of the MySQL source database must be set. If the source database version is MySQL 5.6 or earlier, the server_id value ranges from 2 to 4294967296. If the source database is MySQL 5.7, the server_id value ranges from 1 to 4294967296.
  • During an incremental synchronization, if the session variable character_set_client is set to binary, some data may include garbled characters.
  • The database and table names in the source database cannot contain non-ASCII characters, or special characters '<`>/\

Destination database

  • The destination database is a Kafka database.

Precautions

  • Objects that have dependencies must be synchronized at the same time to avoid synchronization failure. Common dependencies: tables referenced by views, views referenced by views, views and tables referenced by stored procedures/functions/triggers, and tables referenced by primary and foreign keys
  • If a full synchronization task is suspended or resumed due to an exception, there may be duplicate data in the destination Kafka. Use the identifier field in the Kafka data for data deduplication. (The shard ID must be unique.)
  • Cascade operations cannot be performed on tables with foreign keys. If the foreign key index of a table is a common index, the table structure may fail to be created. You are advised to use a unique index.
  • Binlogs cannot be forcibly deleted. Otherwise, the synchronization task fails.
  • The source database does not support the reset master or reset master to command, which may cause DRS task failures or data inconsistency.
  • If the source MySQL database does not support TLS 1.2 or is a self-built database of an earlier version (earlier than 5.6.46 or between 5.7.0 and 5.7.28), you need to submit an O&M application for testing the SSL connection.
  • Before creating a DRS task, if concurrency control rules of SQL statements are configured for the source database, the DRS task may fail.
  • During the synchronization, do not delete or change the username, password, or permission of the source database, or change the port of the destination database.
  • Data inconsistency may occur when the MyISAM table is modified during synchronization.
  • During synchronization of table-level objects, renaming tables is not recommended.
  • During database name mapping, if the objects to be synchronized contain stored procedures, views, and functions, these objects cannot be synchronized in the full synchronization phase.

Procedure

  1. On the Data Synchronization Management page, click Create Synchronization Task.
  2. On the Create Synchronization Instance page, specify the task name, description, and the synchronization instance details, and click Create Now.

    • Task information description
      Table 3 Task and recipient description

      Parameter

      Description

      Task Name

      The task name must start with a letter and consist of 4 to 50 characters. It can contain only letters, digits, hyphens (-), and underscores (_).

      Description

      The description consists of a maximum of 256 characters and cannot contain special characters !=<>'&"\

    • Synchronization instance details
      Table 4 Synchronization instance settings

      Parameter

      Description

      Data Flow

      Choose Self-built to self-built.

      Source DB Engine

      Select MySQL.

      Destination DB Engine

      Select Kafka.

      Network Type

      The Public network is used as an example. Available options: VPC, Public network and VPN or Direct Connect

      VPC

      Select an available VPC.

      Synchronization Instance Subnet

      Select the subnet where the synchronization instance is located. You can also click View Subnet to go to the network console to view the subnet where the instance resides.

      By default, the DRS instance and the destination DB instance are in the same subnet. You need to select the subnet where the DRS instance resides and ensure that there are available IP addresses. To ensure that the synchronization instance is successfully created, only subnets with DHCP enabled are displayed.

      Security Group

      Select a security group. You can use security group rules to allow or deny access to the instance.

      Synchronization Mode

      Available options: Full+Incremental and Incremental

      • Full+Incremental

        This synchronization mode allows you to synchronize data in real time. After a full synchronization initializes the destination database, an incremental synchronization parses logs to ensure data consistency between the source and destination databases.

      • Incremental

        Through log parsing, incremental data generated on the source database is synchronized to the destination database.

    • Task Type
      Table 5 Task type information

      Parameter

      Description

      AZ

      Select the AZ where you want to create the DRS task. Selecting the one housing the source or destination database can provide better performance.

      If DRS Task Type is set to Dual-AZ, you can specify Primary AZ and Standby AZ.

    If a task fails to be created, DRS retains the task for three days by default. After three days, the task automatically ends.

  3. On the Configure Source and Destination Databases page, wait until the synchronization instance is created. Then, specify source and destination database information and click Test Connection for both the source and destination databases to check whether they have been connected to the synchronization instance. After the connection tests are successful, select the check box before the agreement and click Next.

    Table 6 Source database settings

    Parameter

    Description

    IP Address or Domain Name

    The IP address or domain name of the source database.

    Port

    The port of the source database. Range: 1 – 65535

    Database Username

    The username for accessing the source database.

    Database Password

    The password for the database username.

    SSL Connection

    SSL encrypts the connections between the source and destination databases. If SSL is enabled, upload the SSL CA root certificate.

    NOTE:
    • The maximum size of a single certificate file that can be uploaded is 500 KB.
    • If SSL is disabled, your data may be at risk.

    The username and password of the source database are encrypted and stored in DRS and will be cleared after the task is deleted.

    Table 7 Destination database settings

    Parameter

    Description

    IP Address or Domain Name

    The IP address or domain name of the destination database.

    Security Protocol

    Available options: PLAINTEXT, SSL, SASL_PLAINTEXT, and SASL_SSL. For details, see Kafka Authentication.

  4. On the Set Synchronization Task page, select the synchronization policy, objects, and data format, and click Next.

    Table 8 Synchronization Object

    Parameter

    Description

    Flow Control

    You can choose whether to control the flow.

    • Yes

      You can customize the maximum synchronization speed.

      In addition, you can set the time range based on your service requirements. The traffic rate setting usually includes setting of a rate limiting time period and a traffic rate value. Flow can be controlled all day or during specific time ranges. The default value is All day. A maximum of three time ranges can be set, and they cannot overlap.

      The flow rate must be set based on the service scenario and cannot exceed 9,999 MB/s.

    • No
      The synchronization speed is not limited and the outbound bandwidth of the source database is maximally used, which will increase the read burden on the source database. For example, if the outbound bandwidth of the source database is 100 MB/s and 80% bandwidth is used, the I/O consumption on the source database is 80 MB/s.
      NOTE:
      • The flow control mode takes effect only in the full synchronization phase.
      • You can also change the flow control mode after creating a task. For details, see Modifying the Flow Control Mode.

    Synchronization Object Type

    Available options: Table structure and Data

    Synchronize DML

    Select the DML operations to be synchronized. By default, all DML operations are selected.

    Topic Synchronization Policy

    Topic synchronization policy. You can select A specific topic or Auto-generated topics.

    Topic

    Select the topic to be synchronized to the destination database. This parameter is available when the topic is set to A specified topic.

    Topic Name Format

    Topic name format. This parameter is available when Topic Synchronization Policy is set to Auto-generated topics.

    Due to Kafka restrictions, a topic name can contain only ASCII characters, periods (.), underscores (_), and hyphens (-). If a topic name exceeds the limit, the topic fails to be created and the task is abnormal.

    If a topic name contains a database object name, ensure that the characters in the object name meet the Kafka topic naming requirements.

    Only variables database and tablename are supported. The other characters must be constants. Replace $database$ with the database name and $tablename$ with the table name.

    For example, if this parameter is set to $database$-$tablename$ and the database name is db1, and the table name is tab1, the topic name is db1-tab1. If DDL statements are synchronized, $tablename$ is empty and the topic name is db1.

    Number of Partitions

    This parameter is available when Topic Synchronization Policy is set to Auto-generated topics.

    The number of partitions of a topic. Each topic can have multiple partitions. More partitions can provide higher throughput but consume more resources. Set the number of partitions based on the actual situation of brokers.

    Replication Factor

    This parameter is available when Topic Synchronization Policy is set to Auto-generated topics.

    Number of copies of a topic. Each topic can have multiple copies, and the copies are placed on different brokers in a cluster. The number of copies cannot exceed the number of brokers. Otherwise, the topic fails to be created.

    Synchronize Topic To

    The policy for synchronizing topics to the Kafka partitions.

    • If topics are synchronized to different partitions by hash value of the database and table names, the performance on a single table query can be improved.
    • If topics are synchronized to partition 0, strong consistency can be obtained but write performance is impacted.
    • If topics are synchronized to different partitions by hash value of the primary key, one table corresponds to one topic.

    Data Format in Kafka

    Select the data format to be delivered from MySQL to Kafka.

    • Avro refers to binary encoded format. This option is available only when Synchronization Mode is set to Incremental in 2.
    • JSON: JSON message format, which is easy to interpret but takes up more space.
    • JSON-C: A data format that is compatible with multiple batch and stream computing frameworks.

    For details, see Kafka Message Format.

    Synchronization Object

    The left pane displays the source database objects, and the right pane displays the selected objects. You can select Tables, Import object file, or Databases for Synchronization Object as required.

    • If the synchronization objects in source and destination databases have different names, you can map the source object name to the destination one. For details, see Mapping Object Names.
    • For details about how to import an object file, see Importing Synchronization Objects.
    NOTE:
    • To quickly select the desired database objects, you can use the search function.
    • If there are changes made to the source databases or objects, click in the upper right corner to update the objects to be synchronized.
    • If the object name contains spaces, the spaces before and after the object name are not displayed. If there are multiple spaces between the object name and the object name, only one space is displayed.
    • The name of the selected synchronization object cannot contain spaces.

  5. On the Process Data page, select the columns to be processed.

    • If data processing is not required, click Next.
    • If you need to process columns, set processing rules by referring to Processing Data.

  6. On the Check Task page, check the synchronization task.

    • If any check fails, review the cause and rectify the fault. After the fault is rectified, click Check Again.
    • If all check items are successful, click Next.

      You can proceed to the next step only when all checks are successful. If there are any items that require confirmation, view and confirm the details first before proceeding to the next step.

  7. On the displayed page, specify Start Time, confirm that the configured information is correct, and click Submit to submit the task.

    Table 9 Task startup settings

    Parameter

    Description

    Start Time

    Set Start Time to Start upon task creation or Start at a specified time based on site requirements.

    NOTE:

    After a synchronization task is started, the performance of the source and destination databases may be affected. You are advised to start a synchronization task during off-peak hours.

  8. After the task is submitted, you can view and manage it on the Data Synchronization Management page.

    • You can view the task status. For more information about task status, see Task Statuses.
    • You can click in the upper-right corner to view the latest task status.
    • By default, DRS retains any task in the Configuration state for three days. After three days, DRS automatically deletes background resources, but the task status remains unchanged. When you configure the task again, DRS applies for resources for the task again. In this case, the IP address of the DRS instance changes.