8.14.7 Replication Replica SQL Thread States

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

• 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

  The thread has processed all events in the relay log files, and is now waiting for the I/O thread to write new events to the relay log.

• Waiting for an event from Coordinator

  Using the multithreaded replica (slave_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

  A very brief state that occurs as the thread is stopping.

• Waiting for Slave Workers to free pending events

  This waiting action occurs when the total size of events being processed by Workers exceeds the size of the slave_pending_jobs_size_max system variable. The Coordinator resumes scheduling when the size drops below this limit. This state occurs only when slave_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 MASTER_DELAY seconds after master executed event

  The SQL thread has read an event but is waiting for the replica delay to lapse. This delay is set with the MASTER_DELAY option of CHANGE MASTER 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.