If the replica is not multithreaded, this table shows the
status of the applier thread. Otherwise, the replica uses
multiple worker threads and a coordinator thread to manage
them, and this table shows the status of the worker threads.
For a multithreaded replica, the
table shows the status of the coordinator thread.
table has these columns:
The replication channel which this row is displaying. There is always a default replication channel, and more replication channels can be added. See Replication Channels for more information.
The worker identifier (same value as the
idcolumn in the
STOP SLAVE, the
NULL, but the
WORKER_IDvalue is preserved.
The worker thread identifier.
ON(thread exists and is active or idle) or
OFF(thread no longer exists).
The transaction that the worker has last seen. The worker has not necessarily applied this transaction because it could still be in the process of doing so.
gtid_modesystem variable value is
OFF, this column is
ANONYMOUS, indicating that transactions do not have global transaction identifiers (GTIDs) and are identified by file and position only.
ON, the column value is defined as follows:
If no transaction has executed, the column is empty.
The GTID is preserved until the next transaction is executed. If an error occurs, the column value is the GTID of the transaction being executed by the worker when the error occurred. The following statement shows whether or not that transaction has been committed:
SELECT GTID_SUBSET(LAST_SEEN_TRANSACTION, @@GLOBAL.GTID_EXECUTED) FROM performance_schema.replication_applier_status_by_worker;
If the statement returns zero, the transaction has not yet been committed, either because it is still being processed, or because the worker thread was stopped while it was being processed. If the statement returns nonzero, the transaction has been committed.
The error number and error message of the most recent error that caused the worker thread to stop. An error number of 0 and message of the empty string mean “no error”. If the
LAST_ERROR_MESSAGEvalue is not empty, the error values also appear in the replica's error log.
All error codes and messages displayed in the
LAST_ERROR_MESSAGEcolumns correspond to error values listed in Server Error Message Reference.
A timestamp in
YYMMDD hh:mm:ssformat that shows when the most recent worker error occurred.
The following table shows the correspondence between
SHOW SLAVE STATUS