The thread is trying to reconnect to the source. When connection is established again, the state becomes Waiting for master to send event . 

• Registering slave on master 

A state that occurs very briefly after the connection to the source is established. 

• Requesting binlog dump 

A state that occurs very briefly, after the connection to the source is established. The thread sends to the source a request for the contents of its binary logs, starting from the requested binary log file name and position. 

• Waiting for its turn to commit 

A state that occurs when the replica thread is waiting for older worker threads to commit if slave_preserve_commit_order  is enabled. 

• Waiting for master to send event 

The thread has connected to the source and is waiting for binary log events to arrive. This can last for a long time if the source is idle. If the wait lasts for slave_net_timeout  seconds, a timeout occurs. At that point, the thread considers the connection to be broken and makes an attempt to reconnect. 

• Waiting for master update 

The initial state before Connecting to master . 

• Waiting for slave mutex on exit 

A state that occurs briefly as the thread is stopping. 

• Waiting for the slave SQL thread to free enough relay log space 

You are using a nonzero relay_log_space_limit  value, and the relay logs have grown large enough that their combined size exceeds this value. The I/O thread is waiting until the SQL thread frees enough space by processing relay log contents so that it can delete some relay log files. 

• Waiting to reconnect after a failed binlog dump request 

If the binary log dump request failed (due to disconnection), the thread goes into this state while it sleeps, then tries to reconnect periodically. The interval between retries can be specified using the the CHANGE REPLICATION SOURCE TO  statement (from MySQL 8.0.23) or CHANGE MASTER TO statement (before MySQL 8.0.23). 

• Waiting to reconnect after a failed master event read 

An error occurred while reading (due to disconnection). The thread is sleeping for the number of seconds set by the the CHANGE REPLICATION SOURCE TO  statement (from MySQL 8.0.23) or CHANGE MASTER TO  statement (before MySQL 8.0.23), which defaults to 60, before attempting to reconnect. 

## 8.14.6 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: 

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

