This topic provides answers to some frequently asked questions about data synchronization to Hologres.

What do I do if the PolarDB data source cannot be connected?

  • Problem description: The connectivity test fails when I add a PolarDB data source.
  • Solution: Set Data source type to Connection string mode and check the whitelist configuration of the PolarDB cluster and the virtual private cloud (VPC) configuration of your exclusive resource group.

What do I do if the connectivity test fails for the Oracle data source?

  • Problem description: The connectivity test fails when I add an Oracle data source.
  • Solution: Set Data source type to Connection string mode and check the whitelist configuration of the PolarDB cluster and the virtual private cloud (VPC) configuration of your exclusive resource group.

What do I do if the connectivity test fails for the MySQL data source?

  • Problem description: The connectivity test fails when I add a MySQL data source.
  • Solution: Set Data source type to Connection string mode and check the whitelist configuration of the PolarDB cluster and the virtual private cloud (VPC) configuration of your exclusive resource group.

The system displays the following error message for a real-time synchronization node: "com.alibaba.otter.canal.parse.exception.PositionNotFoundException: can't find start position for XXX." What do I do?

  • Problem description: The real-time synchronization node fails to run, and the system displays the error message "com.alibaba.otter.canal.parse.exception.PositionNotFoundException: can't find start position for XXX."
  • Cause: The binary logging feature is disabled for the PolarDB data source.
  • Solution: Enable the binary logging feature for the PolarDB data source. For more information, see Configure a data source (PolarDB). Change one or more data records and change the start time for running the real-time data synchronization node to the current time.

The system displays the following error message for a real-time data synchronization node: "com.alibaba.otter.canal.parse.exception.CanalParseException: command : 'show master status' has an error! pls check. you need (at least one of) the SUPER,REPLICATION CLIENT privilege(s) for this operation." What do I do?

  • Problem description: The real-time synchronization node fails to run, and the system displays the error message "com.alibaba.otter.canal.parse.exception.CanalParseException: command : 'show master status' has an error! pls check. you need (at least one of) the SUPER,REPLICATION CLIENT privilege(s) for this operation."
  • Cause: The account used to synchronize data is not authorized to access the PolarDB data source, or the PolarDB database connected is not deployed on the PolarDB Writer node.
  • Solution: Authorize the account to access the PolarDB data source. For more information, see Configure a data source (PolarDB). You can also check whether the PolarDB database connected is deployed on the PolarDB Writer node. When a real-time data synchronization node is run, the system cannot capture data from the PolarDB Reader nodes of the PolarDB cluster.

The system displays the following error message for a real-time data synchronization node: "com.alibaba.datax.plugin.reader.mysqlbinlogreader.MysqlBinlogReaderException: The mysql server does not enable the binlog write function. Please enable the mysql binlog write function first." What do I do?

  • Problem description: The real-time synchronization node fails to run, and the system displays the error message "com.alibaba.datax.plugin.reader.mysqlbinlogreader.MysqlBinlogReaderException: The mysql server does not enable the binlog write function. Please enable the mysql binlog write function first."
  • Cause: The loose_polar_log_bin parameter is not specified for the PolarDB data source.
  • Solution: Specify the loose_polar_log_bin parameter. For more information, see Configure a data source (PolarDB).

The system displays the following error message for the batch synchronization node: "com.alibaba.datax.common.exception.DataXException: Code:[HoloWriter-02], Description:[Invalid config parameter in your configuration.]. - Field _log_file_name_offset_ not allow null but not present in user configured columns." What do I do?

  • Problem description: The batch synchronization node fails to run, and the system displays the error message "com.alibaba.datax.common.exception.DataXException: Code:[HoloWriter-02], Description:[Invalid config parameter in your configuration.]. - Field _log_file_name_offset_ not allow null but not present in user configured columns."
  • Cause: The engine-type plug-in of DataWorks for batch synchronization is not upgraded to the latest version.
  • Solution: Submit a ticket to upgrade your plug-in.

The system displays the following error message for the batch synchronization node: "errorCode:NoSuchTopic, errorMessage:The specified topic name does not exist." What do I do?

  • Problem description: The batch synchronization node fails to run, and the system displays the error message "errorCode:NoSuchTopic, errorMessage:The specified topic name does not exist."
  • Causes:
    • The destination Hologres table used for data synchronization does not exist.
    • The data synchronization node synchronizes data of the source table to a Hologres external table. The Hologres Writer node cannot write data to Hologres external tables.
  • Solution: Use a Hologres internal table as the destination table for data synchronization. If the destination Hologres table does not exist, set Table creation method to Create Table when you configure a data synchronization node. Then, the destination Hologres table is automatically created. For more information, see Configure and view a data synchronization solution.