MySQL :: MySQL 8.0 Reference Manual :: 29.12.11.5 The replication_applier_status_by_worker Table (original) (raw)

29.12.11.5 The replication_applier_status_by_worker Table

This table provides details of the transactions handled by applier threads on a replica or Group Replication group member. For a single-threaded replica, data is shown for the replica's single applier thread. For a multithreaded replica, data is shown individually for each applier thread. The applier threads on a multithreaded replica are sometimes called workers. The number of applier threads on a replica or Group Replication group member is set by thereplica_parallel_workers orslave_parallel_workers system variable, which is set to zero for a single-threaded replica. A multithreaded replica also has a coordinator thread to manage the applier threads, and the status of this thread is shown in thereplication_applier_status_by_coordinator table.

All error codes and messages displayed in the columns relating to errors correspond to error values listed inServer Error Message Reference.

When the Performance Schema is disabled, local timing information is not collected, so the fields showing the start and end timestamps for applied transactions are zero. The start timestamps in this table refer to when the worker started applying the first event, and the end timestamps refer to when the last event of the transaction was applied.

When a replica is restarted by aSTART REPLICA statement, the columns beginningAPPLYING_TRANSACTION are reset. Before MySQL 8.0.13, these columns were not reset on a replica that was operating in single-threaded mode, only on a multithreaded replica.

Thereplication_applier_status_by_worker table has these columns:

• CHANNEL_NAME
  The replication channel which this row is displaying. There is always a default replication channel, and more replication channels can be added. SeeSection 19.2.2, “Replication Channels” for more information.
• WORKER_ID
  The worker identifier (same value as theid column in themysql.slave_worker_info table). AfterSTOP REPLICA, the THREAD_ID column becomes NULL, but theWORKER_ID value is preserved.
• THREAD_ID
  The worker thread ID.
• SERVICE_STATE
ON (thread exists and is active or idle) or OFF (thread no longer exists).
• LAST_ERROR_NUMBER,LAST_ERROR_MESSAGE
  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 theLAST_ERROR_MESSAGE value is not empty, the error values also appear in the replica's error log.
  Issuing RESET MASTER orRESET REPLICA resets the values shown in these columns.
• LAST_ERROR_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format that shows when the most recent worker error occurred.
• LAST_APPLIED_TRANSACTION
  The global transaction ID (GTID) of the last transaction applied by this worker.
• LAST_APPLIED_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format that shows when the last transaction applied by this worker was committed on the original source.
• LAST_APPLIED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format that shows when the last transaction applied by this worker was committed on the immediate source.
• LAST_APPLIED_TRANSACTION_START_APPLY_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format that shows when this worker started applying the last applied transaction.
• LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format that shows when this worker finished applying the last applied transaction.
• APPLYING_TRANSACTION
  The global transaction ID (GTID) of the transaction this worker is currently applying.
• APPLYING_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format that shows when the transaction this worker is currently applying was committed on the original source.
• APPLYING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format that shows when the transaction this worker is currently applying was committed on the immediate source.
• APPLYING_TRANSACTION_START_APPLY_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format that shows when this worker started its first attempt to apply the transaction that is currently being applied. Before MySQL 8.0.13, this timestamp was refreshed when a transaction was retried due to a transient error, so it showed the timestamp for the most recent attempt to apply the transaction.
• LAST_APPLIED_TRANSACTION_RETRIES_COUNT
  The number of times the last applied transaction was retried by the worker after the first attempt. If the transaction was applied at the first attempt, this number is zero.
• LAST_APPLIED_TRANSACTION_LAST_TRANSIENT_ERROR_NUMBER
  The error number of the last transient error that caused the transaction to be retried.
• LAST_APPLIED_TRANSACTION_LAST_TRANSIENT_ERROR_MESSAGE
  The message text for the last transient error that caused the transaction to be retried.
• LAST_APPLIED_TRANSACTION_LAST_TRANSIENT_ERROR_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format for the last transient error that caused the transaction to be retried.
• APPLYING_TRANSACTION_RETRIES_COUNT
  The number of times the transaction that is currently being applied was retried until this moment. If the transaction was applied at the first attempt, this number is zero.
• APPLYING_TRANSACTION_LAST_TRANSIENT_ERROR_NUMBER
  The error number of the last transient error that caused the current transaction to be retried.
• APPLYING_TRANSACTION_LAST_TRANSIENT_ERROR_MESSAGE
  The message text for the last transient error that caused the current transaction to be retried.
• APPLYING_TRANSACTION_LAST_TRANSIENT_ERROR_TIMESTAMP
  A timestamp in '_`YYYY-MM-DD hh:mm:ss`_[._`fraction`_]' format for the last transient error that caused the current transaction to be retried.

Thereplication_applier_status_by_worker table has these indexes:

• Primary key on (CHANNEL_NAME,WORKER_ID)
• Index on (THREAD_ID)

The following table shows the correspondence betweenreplication_applier_status_by_worker columns andSHOW REPLICA STATUS columns.