This topic describes how to synchronize data from a self-managed PostgreSQL database to an ApsaraDB RDS for PostgreSQL instance by using Data Transmission Service (DTS).

Prerequisites

  • A self-managed PostgreSQL database and an ApsaraDB RDS for PostgreSQL instance are created. For information about how to create the destination ApsaraDB RDS for PostgreSQL instance, see Create an ApsaraDB RDS for PostgreSQL instance. For information about the supported versions, see Overview of data synchronization scenarios.
    Note To ensure compatibility, the version of the destination database must be the same as or later than the version of the source database.

    If the version of the destination database is earlier than the version of the source database, database compatibility issues may occur.

  • The available storage space of the destination ApsaraDB RDS for PostgreSQL instance is larger than the total size of the data in the self-managed PostgreSQL database.

Limits

Supported synchronization topologies

  • One-way one-to-one synchronization
  • One-way one-to-many synchronization
  • One-way cascade synchronization
  • One-way many-to-one synchronization

For more information, see Synchronization topologies.

SQL operations that can be synchronized

Operation type SQL statements
DML INSERT, UPDATE, and DELETE

Permissions required for database accounts

Database Required permissions References
Self-managed PostgreSQL databases The permissions of the superuser role CREATE USER and GRANT
ApsaraDB RDS for PostgreSQL instance The permissions of the schema owner ApsaraDB RDS for PostgreSQL Create an account on an ApsaraDB RDS for PostgreSQL instance

Before you begin

If the version of the self-managed PostgreSQL database is 9.4.8 to 10.0, you must perform the following operations before you configure a data synchronization task.
  1. Download the PostgreSQL source code from the official website, and compile and install the source code.
    1. Download the source code from the PostgreSQL official website based on the version of the self-managed PostgreSQL database.
    2. Run the ./configure, make, and make install commands to in sequence to configure, compile, and install the source code.
      Notice
      • When you compile and install PostgreSQL, the operating system version of PostgreSQL must be consistent with the GNU Compiler Collection (GCC) version.
      • If an error occurs when you run the ./configure command, you can adjust the command based on the error message. For example, if the error message is readline library not found. Use --without-readline to disable readline support., you can change the command to ./configure --without-readline.
      • If you use other methods to install PostgreSQL, you must compile the ali_decoding plug-in in a test environment that has the same OS version and GCC version.
  2. Download the ali_decoding plug-in provided by DTS, and compile and install the plug-in.
    1. Download ali_decoding.
    2. Copy the ali_decoding directory to the contrib directory of PostgreSQL (compiled and installed).
      contrib directory
    3. Go to the ali_decoding directory and replace the content of the Makefile file with the following script:
      # contrib/ali_decoding/Makefile
      MODULE_big = ali_decoding
      MODULES = ali_decoding
      OBJS    = ali_decoding.o
      
      DATA = ali_decoding--0.0.1.sql ali_decoding--unpackaged--0.0.1.sql
      
      EXTENSION = ali_decoding
      
      NAME = ali_decoding
      
      #subdir = contrib/ali_decoding
      #top_builddir = ../..
      #include $(top_builddir)/src/Makefile.global
      #include $(top_srcdir)/contrib/contrib-global.mk
      
      #PG_CONFIG = /usr/pgsql-9.6/bin/pg_config
      #pgsql_lib_dir := $(shell $(PG_CONFIG) --libdir)
      #PGXS := $(shell $(PG_CONFIG) --pgxs)
      #include $(PGXS)
      
      # Run the following commands to install the source code.
      ifdef USE_PGXS
      PG_CONFIG = pg_config
      PGXS := $(shell $(PG_CONFIG) --pgxs)
      include $(PGXS)
      else
      subdir = contrib/ali_decoding
      top_builddir = ../..
      include $(top_builddir)/src/Makefile.global
      include $(top_srcdir)/contrib/contrib-global.mk
      endif
    4. Go to the ali_decoding directory, run the make and make install commands in sequence to compile ali_decoding and obtain the files required to install ali_decoding.
    5. Copy the following files to the specified location.
      Specify location
  3. Create a database and schema in the destination ApsaraDB RDS for PostgreSQL instance based on the database and schema information of the objects to be synchronized. The schema name of the source and destination databases must be the same. For more information, see Create a database on an ApsaraDB RDS for PostgreSQL instance and Appendix: User and schema management.
If the version of the self-managed PostgreSQL database is 10.1 to 13, you must perform the following operations before you configure a data synchronization task.
  1. Log on to the server where the self-managed PostgreSQL database resides.
  2. Set the value of the wal_level parameter in the postgresql.conf configuration file to logical.
    Set the wal_level parameter
  3. Add the CIDR blocks of DTS servers to the pg_hba.conf configuration file of the self-managed PostgreSQL database. Add only the CIDR blocks of the DTS servers that reside in the same region as the destination database. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
    Note For more information, see The pg_hba.conf File. Skip this step if you have set the IP address in the pg_hba.conf file to 0.0.0.0/0.
  4. Create a database and schema in the destination ApsaraDB RDS for PostgreSQL instance based on the database and schema information of the objects to be synchronized. The schema name of the source and destination databases must be the same. For more information, see Create a database on an ApsaraDB RDS for PostgreSQL instance and Appendix: User and schema management.

Procedure

  1. Go to the Data Synchronization page of the new DTS console.
    Note You can also log on to the Data Management (DMS) console. In the top navigation bar, choose DTS > Data Synchronization.
  2. In the upper-left corner of the page, select the region where the data synchronization instance resides.
    Select a region
  3. Click Create Task. On the page that appears, configure the source and destination databases.
    Warning After you select the source and destination instances, we recommend that you read the limits displayed at the top of the page. This helps you create and run the data synchronization task.
    Configure the source and destination databases
    Section Parameter Description
    N/A Task Name

    DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to use a unique task name.

    Source Database Select Template
    If the connection settings of the instance has been saved as a template, you can select the connection name. DTS automatically applies the saved connection settings.
    Note
    • You can modify the connection settings of a template.
    • To edit the template name, you can click Edit Template Name at the bottom of the Source Database section.
    • The modified connection template will take effect the next time you select the connection template. The database instance that you have configured by using the template is not affected.
    Database Type Select PostgreSQL.
    Access Method Select Cloud Enterprise Network (CEN).
    Instance Region Select the region where the self-managed PostgreSQL database resides.
    CEN Instance ID Select the ID of the CEN instance that hosts the self-managed PostgreSQL database.
    Connected VPC Select the virtual private cloud (VPC) that is connected to the self-managed PostgreSQL database.
    IP Address Enter the server IP address of the self-managed PostgreSQL database.
    Port Number Enter the service port number of the self-managed PostgreSQL database. The default port number is 5432.
    Database Name Enter the name of the self-managed PostgreSQL database.
    Database Account Enter the account that is used to log on to the self-managed PostgreSQL database. For information about the permissions that are required for the account, see Permissions required for database accounts.
    Database Password

    Enter the password of the database account.

    Save as Template
    Click Save as Template. In the dialog box that appears, set the name of the database connection, and click OK. The connection settings of the database instance is saved as a template.
    Note We recommend that you specify an informative name to identify the database connection. You do not need to use a unique name.
    Destination Database Select Template
    If the connection settings of the instance has been saved as a template, you can select the connection name. DTS automatically applies the saved connection settings.
    Note
    • You can modify the connection settings of a template.
    • To edit the template name, you can click Edit Template Name at the bottom of the Source Database section.
    • The modified connection template will take effect the next time you select the connection template. The database instance that you have configured by using the template is not affected.
    Database Type Select PostgreSQL.
    Access Method Select Alibaba Cloud Instance.
    Instance Region Select the region where the destination ApsaraDB RDS for PostgreSQL instance resides.
    Instance ID Select the ID of the destination ApsaraDB RDS for PostgreSQL instance.
    Database Name Enter the name of the destination database in the ApsaraDB RDS for PostgreSQL instance.
    Database Account Enter the database account of the destination ApsaraDB RDS for PostgreSQL instance. For information about the permissions that are required for the account, see Permissions required for database accounts.
    Database Password

    Enter the password of the database account.

    Save as Template
    Click Save as Template. In the dialog box that appears, set the name of the database connection, and click OK. The connection settings of the database instance is saved as a template.
    Note We recommend that you specify an informative name to identify the database connection. You do not need to use a unique name.
  4. In the lower part of the page, click Test Connectivity and Proceed.
  5. Select objects for the task and configure advanced settings.
    • Basic SettingsBasic Settings
      Parameter Description
      Task Stages

      Incremental Data Synchronization is selected by default. You must also select Schema Synchronization and Full Data Synchronization. After the precheck, DTS synchronizes the historical data of the selected objects from the source instance to the destination cluster. The historical data is the basis for subsequent incremental synchronization.

      Processing Mode of Conflicting Tables
      • Precheck and Report Errors: checks whether the destination database contains tables that have the same names as tables in the source database. If the source and destination databases do not contain identical table names, the precheck is passed. Otherwise, an error is returned during precheck and the data synchronization task cannot be started.

        Note You can use the object name mapping feature to rename the tables that are synchronized to the destination database. You can use this feature if the source and destination databases contain identical table names and the tables in the destination database cannot be deleted or renamed. For more information, see Map object names.
      • Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases.
        Warning If you select Ignore Errors and Proceed, data consistency is not guaranteed and your business may be exposed to potential risks.
        • If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database:
          • During full data synchronization, DTS does not synchronize the data record to the destination database. The existing data record in the destination database is retained.
          • During incremental data synchronization, DTS synchronizes the data record to the destination database. The existing data record in the destination database is overwritten.
        • If the source and destination databases have different schemas, data may fail to be initialized. In this case, only some columns are synchronized or the data synchronization task fails.
      Synchronization Topology

      Select One-way Synchronization.

      Select Objects

      Select one or more objects from the Source Objects section and click the Rightwards arrow icon to move the objects to the Selected Objects section.

      Note You can select columns, tables, or schemas as the objects to be synchronized.
      Rename Databases and Tables
      • To rename an object that you want to synchronize to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object.
      • To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.
      Filter data

      You can specify WHERE conditions to filter data. For more information, see Use SQL conditions to filter data.

      Select the SQL operations to be synchronized In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations that you want to synchronize. For more information, see SQL operations that can be synchronized.
    • Advanced SettingsAdvanced Settings
      Parameter Description
      Set Alerts
      Specify whether to set alerts for the data synchronization task. If the task fails or the synchronization latency exceeds the threshold, the alert contacts will receive notifications.
      • Select No if you do not want to set alerts.
      • Select Yes to set alerts. In this case, you must also set the alert threshold and alert contacts.
      Capitalization of Object Names in Destination Instance

      Specify the capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that of the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.

      Retry Time for Failed Connection
      Specify the retry time for failed connections. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the retry time to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified time, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails.
      Note
      • If multiple DTS instances have the same source or destination database, the lowest value takes effect. For example, the retry time is set to 30 minutes for Instance A and 60 minutes for Instance B, DTS retries failed connections at an interval of 30 minutes.
      • When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time based on your business needs. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
  6. Click Next: Save Task Settings and Precheck in the lower part of the page.
    Note
    • Before you can start the data synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.
    • If the task fails to pass the precheck, you can click the Info icon icon next to each failed item to view details.
      • You can troubleshoot the issues based on the causes and run a precheck again.
      • If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
  7. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
  8. On the Purchase Instance page, specify the Billing Method and Instance Class parameters for the data synchronization instance. The following table describes the parameters.
    Section Parameter Description
    Parameters Billing Method
    • Subscription: You can pay for your subscription when you create an instance. We recommend that you select the subscription billing method for long-term use because it is more cost-effective than the pay-as-you-go billing method. You can save more costs with longer subscription periods.
    • Pay-as-you-go: A pay-as-you-go instance is billed on an hourly basis. We recommend that you select the pay-as-you-go billing method for short-term use. If you no longer require your pay-as-you-go instance, you can release it to reduce costs.
    Instance Class DTS provides several instance classes that have different performance in synchronization speed. You can select an instance class based on your business scenario. For more information, see Specifications of data synchronization instances.
    Subscription Length If you select the subscription billing method, set the subscription length and the number of instances that you want to create. The subscription length can be one to nine months or one to three years.
    Note This parameter is available only if you select the subscription billing method.
  9. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
  10. Click Buy and Start to start the data synchronization task. You can view the progress of the task in the task list.