This topic provides answers to some commonly 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 a PolarDB data source is added.
  • Solution: Set Data source type to Connection string mode, 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 the 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.
  • Possible cause: The binary logging feature is disabled for the PolarDB source data source.
  • Solution: Enable the binary logging feature for the PolarDB data source. For more information, see Configure a source PolarDB data source. Change one or more data records and change the start time to run the real-time synchronization node to the current time.

The system displays the following error message for the real-time 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.
  • Possible cause: The account used to synchronize data is not authorized to access the PolarDB source data source, or the PolarDB database connected is not deployed on the primary node.
  • Solution: Authorize the account to access the PolarDB source data source, or check whether the PolarDB database connected is deployed on the primary node. For more information, see Configure a source PolarDB data source. Data capture from the read-only nodes of the PolarDB cluster is not supported.

The system displays the following error message for the real-time 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.
  • Possible cause: The loose_polar_log_bin parameter is not specified for the PolarDB source data source.
  • Solution: Specify the loose_polar_log_bin parameter. For more information, see Configure a source PolarDB data source.

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.
  • Possible 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.