10.14.6 Replication SQL Thread States

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MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4

10.14.6 Replication SQL Thread States

The following list shows the most common states you may see in the State column for a replication SQL thread on a replica server.

In MySQL 8.0, incompatible changes were made to instrumentation names. Monitoring tools that work with these instrumentation names might be impacted. If the incompatible changes have an impact for you, set the terminology_use_previous system variable to BEFORE_8_0_26 to make MySQL Server use the old versions of the names for the objects specified in the previous list. This enables monitoring tools that rely on the old names to continue working until they can be updated to use the new names.

Set the terminology_use_previous system variable with session scope to support individual functions, or global scope to be a default for all new sessions. When global scope is used, the slow query log contains the old versions of the names.

  • Making temporary file (append) before replaying LOAD DATA INFILE

The thread is executing a LOAD DATA statement and is appending the data to a temporary file containing the data from which the replica reads rows. - Making temporary file (create) before replaying LOAD DATA INFILE

The thread is executing a LOAD DATA statement and is creating a temporary file containing the data from which the replica reads rows. This state can only be encountered if the original LOAD DATA statement was logged by a source running a version of MySQL lower than MySQL 5.0.3. - Reading event from the relay log

The thread has read an event from the relay log so that the event can be processed. - Slave has read all relay log; waiting for more updates

Replica has read all relay log; waiting for more updates

The thread has processed all events in the relay log files, and is now waiting for the I/O (receiver) thread to write new events to the relay log. - Waiting for an event from Coordinator

Using the multithreaded replica (replica_parallel_workers is greater than 1), one of the replica worker threads is waiting for an event from the coordinator thread. - Waiting for slave mutex on exit

Waiting for replica mutex on exit

A very brief state that occurs as the thread is stopping. - Waiting for Slave Workers to free pending events

Waiting for Replica Workers to free pending events

This waiting action occurs when the total size of events being processed by Workers exceeds the size of the replica_pending_jobs_size_max system variable. The Coordinator resumes scheduling when the size drops below this limit. This state occurs only when replica_parallel_workers is set greater than 0. - Waiting for the next event in relay log

The initial state before Reading event from the relay log. - Waiting until SOURCE_DELAY seconds after source executed event

The SQL thread has read an event but is waiting for the replica delay to lapse. This delay is set with the SOURCE_DELAY option of the CHANGE REPLICATION SOURCE TO.

The Info column for the SQL thread may also show the text of a statement. This indicates that the thread has read an event from the relay log, extracted the statement from it, and may be executing it.