Help Center/ Data Replication Service/ Real-Time Synchronization/ Out of the Cloud/ From GaussDB(for MySQL) to CSS/ES
Updated on 2024-09-25 GMT+08:00
View PDF
Share

From GaussDB(for MySQL) to CSS/ES

Supported Source and Destination Databases

Table 1 Supported databases

Source DB

Destination DB
  • Primary/standby GaussDB(for MySQL) instances
  • ElasticSearch 5.5, 6.2, 6.5, 7.1, 7.6, 7.9 and 7.10

Only whitelisted users can use this function.

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.
  • You are advised to start your synchronization task during off-peak hours by setting Start Time to Start at a specified time. A less active database is easier to synchronize successfully. If the data is fairly static, there is less likely to be any severe performance impacts during the synchronization.
    • 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.
    • The data being synchronized may be locked by other transactions for a long period of time, resulting in read timeout.
    • Due to the inherent characteristics of MySQL, in certain scenarios the performance may be negatively affected. For example, if the CPU resources are insufficient and the storage engine is TokuDB, the read speed on tables may be decreased by 10%.
    • 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 migration, the exclusive lock on that table may be blocked.
    • For more information about the impact of DRS on databases, see How Does DRS Affect the Source and Destination Databases?
  • Data-Level Comparison

    To obtain accurate comparison results, compare data at a specified time point during off-peak hours. If it is needed, select Start at a specified time for Comparison Time. Due to slight time difference and continuous operations on data, data inconsistency may occur, reducing the reliability and validity of the comparison results.

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 and destination databases, modify the connection information of the DRS task by referring to Modifying Connection Information to prevent automatic retry after a task failure. Automatic retry will lock the database accounts.
Table 2 Precautions

Type

Restrictions

Database permissions

Minimum permission requirements for full plus incremental synchronization:

  • The source database user must have the following permissions:

    SELECT, LOCK TABLES, REPLICATION SLAVE, and REPLICATION CLIENT

  • The destination database user must have the following permissions:

    READ and WRITE

Synchronization object
  • The table data can be synchronized.
  • Databases, views, indexes, constraints, functions, stored procedures, triggers, and events cannot be synchronized.
  • The system database and event status cannot be synchronized.
  • Tables whose primary keys are of the FLOAT type cannot be synchronized.
  • Tables that do not have primary keys cannot be synchronized.
  • Full and incremental synchronizations do not support invisible columns. Invisible columns can be synchronized since MySQL 8.0.23. For example: 
    CREATE TABLE `test11` (
  `id` int NOT NULL,
  `c1` int DEFAULT NULL /*!80023 INVISIBLE */,
  PRIMARY KEY (`id`));

Source database
  • The source database must be the primary node of the primary/standby GaussDB(for MySQL) instance.
  • The source database names cannot contain non-ASCII characters, or the following characters: '<`>/\"
  • The table name in the source database cannot contain non-ASCII characters or the following characters: '<>/\"
  • The column name in the source database cannot contain non-ASCII characters or the following characters: .\"
  • The source database name or mapped name cannot start with ib_logfile or be ib_buffer_pool, ib_doublewrite, ibdata1 or ibtmp1.
  • During the incremental synchronization, the binlog of the source 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 the expire_logs_days value of the source database is set to 0, the synchronization may fail.
  • During an incremental synchronization, the server_id value of the source database must be specified. The value of server_id ranges from 1 to 4294967296.
  • Enable skip-name-resolve for the source database to reduce the possibility of connection timeout.
  • Enable the Global Transaction Identifier (GTID) of the source database.
  • The source database does not support the mysql binlog dump command.
  • The character set of the source database must be the same as that of the destination database. Otherwise, the synchronization fails.
  • The log_slave_updates parameter of the source database must be enabled. Otherwise, the synchronization will fail.
  • The binlog_row_image parameter of the source database must be set to FULL. Otherwise, the synchronization will fail.

Destination database
  • The destination DB instance is running properly.
  • The destination DB instance must have sufficient storage space.

Precautions
  • If the DCC does not support instances with 4 vCPUs and 8 GB memory or higher instance specifications, the synchronization task cannot be created.
  • Before creating a DRS task, if concurrency control rules of SQL statements are configured for the source database, the DRS task may fail.
  • 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.
  • The source database cannot be restored to a point in time when a full synchronization was being performed.
  • Convert the value range of the source database time field that is not supported by the destination database to null.
  • The strings padded with zeros in the source database may be truncated because the source database uses the fixed-length binary data type, and the destination database uses the variable-length data type.
  • The binary value is encrypted using Base64 and then written to the destination database.
  • If no time zone is specified for the source database, specify the time zone for synchronizing the datetime type to the destination database.
  • All table field names are converted to lowercase letters.
  • If the _id field of the destination database is generated using multiple columns in the source database, separate these columns with colons (:).
  • During task startup or full synchronization, you are not advised to perform DDL operations on the source database.
  • To ensure data consistency, you are not allowed to modify the destination database (including but not limited to DDL operations) during synchronization.
  • During synchronization, do not modify or delete the usernames, passwords, permissions, or ports of the source and destination databases.
  • During the synchronization, the source database cannot write data using the statement-based binlog format.
  • During the synchronization, do not clear binlogs on the source database.
  • The source database does not support the reset master or reset master to command, which may cause DRS task failures or data inconsistency.
  • During the synchronization, do not create a database named ib_logfile in the source.
  • During incremental synchronization, if the source database is in a distributed transaction, the synchronization may fail.
  • Incremental synchronization filters out all DDL operations.
  • During incremental synchronization, resumable upload is supported, but data may be repeatedly inserted into non-transactional tables that do not have primary keys when the server system breaks down.
  • If table-level synchronization is selected, tables cannot be renamed during incremental synchronization.
  • Set the expire_log_day parameter 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.
  • When you select synchronization objects, the size of the database table name and column name selected at a time cannot exceed 4 MB. If the number of synchronization objects exceeds the limit, you can add synchronization objects in batches when you re-edit the synchronization objects.

Procedure

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

    • Task information description
      Figure 1 Synchronization task information
      Table 3 Task information

      Parameter

      Description

      Region

      The region where the replication instance is deployed. You can change the region.

      Project

      The project corresponds to the current region and can be changed.

      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
      Figure 2 Synchronization instance details
      Table 4 Synchronization instance settings

      Parameter

      Description

      Data Flow

      Select Out of the cloud.

      Source DB Engine

      Select GaussDB(for MySQL).

      Destination DB Engine

      Select CSS/ES.

      Network Type

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

      • VPC is suitable for data synchronization between cloud databases of the same account in the same region and VPC.
      • Public network is suitable for data synchronization from on-premises or external cloud databases to the destination databases bound with an EIP.
      • VPN or Direct Connect is suitable for data synchronization from on-premises databases to cloud databases, between databases of different accounts in the same region on the cloud, or between databases across regions on the cloud using a VPN, Direct Connect, Cloud Connect, VPCEP, or a VPC peering connection.

      DRS Task Type

      Type of the DRS task. The value can be Single-AZ or Dual-AZ.

      • Dual-AZ: This architecture provides HA, improving the reliability of DRS tasks. After a dual-AZ task is created, DRS creates two subtasks, each running in the primary and standby AZs. If the subtask in the primary AZ fails, DRS automatically starts the subtask in the standby AZ to continue the synchronization. This deployment is for scenarios where there is a lot of service data, long-term synchronization is required, and there are strict limits on how much service downtime can be tolerated.
      • Single-AZ: Single-node deployment is used. The synchronization task will be created on only one node to save money. This deployment is for scenarios where there is a small amount of service data, short-term synchronization is required, and there is no requirement on service downtime.

      This option is available only in specific scenarios. For details, see Performing a Switchover for a Dual-AZ Task.

      Source DB Instance

      The GaussDB(for MySQL) instance you created.

      Synchronization Instance Subnet

      Select the subnet where the synchronization instance is located. You can also click View Subnets 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 there are available IP addresses for the subnet. To ensure that the synchronization instance is successfully created, only subnets with DHCP enabled are displayed.

      Synchronization Mode
      • 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.

      Specify EIP

      This parameter is available when you select Public network for Network Type. Select an EIP to be bound to the DRS instance. DRS will automatically bind the specified EIP to the DRS instance and unbind the EIP after the task is complete. The number of specified EIPs must be the consistent with that of DB instances.

      For details about the data transfer fee generated using a public network, see EIP Price Calculator.
    • Task Type
      Figure 3 Task type
      Table 5 Task type information

      Parameter

      Description

      Specifications

      DRS instance specifications. Different specifications have different performance upper limits. For details, see Real-Time Synchronization.

      NOTE:

      DRS allows you to upgrade specifications only for single-AZ synchronization tasks. Task specifications cannot be downgraded. For details, see Changing Specifications.

      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.

      Figure 4 AZ
    • Enterprise Project and Tags
      Figure 5 Enterprise projects and tags
      Table 6 Enterprise Project and Tags

      Parameter

      Description

      Enterprise Project

      An enterprise project you would like to use to centrally manage your cloud resources and members. Select an enterprise project from the drop-down list. The default project is default.

      For more information about enterprise project, see Enterprise Management User Guide.

      To customize an enterprise project, click Enterprise in the upper right corner of the console. The Enterprise Project Management Service page is displayed. For details, see Creating an Enterprise Project in Enterprise Management User Guide.

      Tags
      • Tags a task. This configuration is optional. Adding tags helps you better identify and manage your tasks. Each task can have up to 20 tags.
      • If your organization has configured tag policies for DRS, add tags to tasks based on the policies. If a tag does not comply with the policies, task creation may fail. Contact your organization administrator to learn more about tag policies.
      • After a task is created, you can view its tag details on the Tags tab. For details, see Tag Management.

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

  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.

    Figure 6 Source database information
    Table 7 Source database settings

    Parameter

    Description

    DB Instance Name

    The GaussDB(for MySQL) instance you selected when creating the task. This parameter cannot be changed.

    Database Username

    The username for accessing the source database.

    Database Password

    The password for the database username.

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

    Figure 7 Destination database information
    Table 8 Destination database settings

    Parameter

    Description

    IP Address or Domain Name

    The IP address or domain name of the destination database.

    Database Username

    The username for accessing the destination 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 root certificate.

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

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

  4. On the Set Synchronization Task page, select the synchronization policy and synchronization object, and click Next.

    Figure 8 Synchronization mode
    Table 9 Synchronization mode and object

    Parameter

    Description

    Flow Control

    You can choose whether to control the flow. Flow Control takes effect in the full phase only.

    • Yes

      You can customize the maximum synchronization speed. During the full synchronization, the synchronization speed of each task (or each subtask in multi-task mode) does not exceed the value of this parameter.

      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 Always. 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.

      Figure 9 Flow control
    • 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

    You can select Table structure or Data for Synchronization Object Type for full synchronization.

    • Data is selected by default.
    • If Table structure is selected, the destination database cannot contain tables whose names are the same as the source tables to be synchronized.
    • If Table structure is not selected, the destination database must have tables that match the source tables, and the table structure must be the same as the selected source table structures.

    Incremental Conflict Policy

    The conflict policy only applies to incremental synchronization. The default value is Overwrite. The conflict in the full synchronization phase is ignored by default.

    Synchronize DML

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

    If you do not select Delete, DELETE statements in the incremental data of the source database will not be synchronized, which may cause a data inconsistency. As a result, there may be a data conflict or the task may fail.

    Shard Configuration

    Configure the number of primary shards and the number of replicas. The default number of primary shards is 5, and the default number of shard replicas is 1.

    Time Zone

    After a time zone is selected, the datatime values are synchronized to CSS/ES with the time zone data.

    Index Name
    • Table Name

      The index name created in the target Elasticsearch instance is the same as the table name.

    • Database Name+Table Name.

      The name of the index created in the target Elasticsearch instance is DatabaseName_TableName.

    Synchronization Object

    The left pane displays the source database objects, and the right pane displays the selected objects. DRS supports table-level synchronization. You can select data for synchronization based on your service requirements.

    • 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 Changing Object Names (Mapping Object Names).
    • When you select synchronization objects, the size of the database table name and column name selected at a time cannot exceed 4 MB. If the number of synchronization objects exceeds the limit, you can add synchronization objects in batches when you re-edit the synchronization objects. For details, see Editing a Synchronization Task.
      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 an object name contains spaces, the spaces before and after the object name are not displayed. If there are two or more consecutive spaces in the middle of the object name, only one space is displayed.
      • The name of the selected synchronization object cannot contain spaces.

  5. On the Process Data page, set the filtering rules for data processing.

    • If data processing is not required, click Next.
    • If data processing is required, select Data filtering or Processing Columns. For details about how to configure related rules, see Processing Data.

      The column processing of the synchronization task from GaussDB(for MySQL) to CSS/ES supports only column filtering and does not support column mapping.

  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.

      For details about how to handle check failures, see Solutions to Failed Check Items in Data Replication Service User Guide.

    • 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, Send Notifications, SMN Topic, Delay Threshold (s), and Stop Abnormal Tasks After, confirm that the configured information is correct, select the check box before the agreement, and click Submit to submit the task.

    Figure 10 Task startup settings

    Table 10 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.

    Send Notifications

    This parameter is optional. After enabled, select a SMN topic. If the status, latency metric, or data of the migration task is abnormal, DRS will send you a notification.

    SMN Topic

    This parameter is available only after you enable Send Notifications and create a topic on the SMN console and add a subscriber.

    For details, see Simple Message Notification User Guide.

    Delay Threshold (s)

    During an incremental synchronization, a synchronization delay indicates a time difference (in seconds) of synchronization between the source and destination database.

    If the synchronization delay exceeds the threshold you specify, DRS will send alarms to the specified recipients. The value ranges from 0 to 3,600. To avoid repeated alarms caused by the fluctuation of delay, an alarm is sent only after the delay has exceeded the threshold for six minutes.

    NOTE:
    • If the delay threshold is set to 0, no notifications will be sent to the recipient.
    • In the early stages of an incremental synchronization, the synchronization delay is long because a large quantity of data is awaiting synchronization. In this case, no notifications will be sent.
    • Before setting the delay threshold, enable Send Notifications.

    Data Exception Notification

    This parameter is optional. After enabled, DRS will send a notification if the task data is abnormal.

    Stop Abnormal Tasks After

    Number of days after which an abnormal task is automatically stopped. The value must range from 14 to 100. The default value is 14.

    NOTE:
    • You can set this parameter only for pay-per-use tasks.
    • Tasks in the abnormal state are still charged. If tasks remain in the abnormal state for a long time, they cannot be resumed. Abnormal tasks run longer than the period you set (unit: day) will automatically stop to avoid unnecessary fees.

  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 a 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.
    • For a public network task, DRS needs to delete background resources after you stop the task. The EIP bound to the task cannot be restored to the Unbound state until background resources are deleted.

Parent topic: Out of the Cloud