<ul><li>MySQL 8.4 and newer have extended the Global Transaction ID (GTID) functionality with a new “tag” option.</li><li>A GTID is a unique ID that is assigned to a transaction. This is used if gtid_mode is set to ON.</li><li>The format of GTIDs is documented here. Before GTID was used replication worked based on a file and offset.</li><li>If you run SET gtid_next='AUTOMATIC:abc then the next transaction will have a GTID that includes the tag.</li><li>Why having a heartbeat tag matters is that losing the data of a heartbeat transaction is fine, while losing a transaction from an application isn’t.</li><li>Binlogs (short for binary logs) are logs of changes made to the database.</li><li>Adding tags impacts a few of the types of events that are sent in the binlog stream.</li><li>There is a new event called GTID_TAGGED_LOG_EVENT that has both new and old interal library</li><li>Replication between 8.4 (or 8.3?) and earlier versions of MySQL breaks when using tagged GTIDs.</li><li>Related bugs have been filed for incomplete internal documentation and behavior mismatch.</li></ul>

MySQL GTID tags and binlog events

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