8.14.6 Replication Replica I/O Thread States
The following list shows the most common states you see in the
State column for a replica server I/O thread. This state also appears in the
Slave_IO_State column displayed by
SHOW SLAVE STATUS, so you can get a good view of what is happening by using that statement.
A state that occurs very briefly, after the connection to the source is established.
The thread is attempting to connect to the source.
The thread has read an event and is copying it to the relay log so that the SQL thread can process it.
The thread is trying to reconnect to the source.
The thread is trying to reconnect to the source. When connection is established again, the state becomes
Waiting for master to send event.
A state that occurs very briefly after the connection to the source is established.
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.
A state that occurs when the replica thread is waiting for older worker threads to commit if
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_timeoutseconds, a timeout occurs. At that point, the thread considers the connection to be broken and makes an attempt to reconnect.
The initial state before
Connecting to master.
A state that occurs briefly as the thread is stopping.
You are using a nonzero
relay_log_space_limitvalue, 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.
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
CHANGE MASTER TOstatement.
An error occurred while reading (due to disconnection). The thread is sleeping for the number of seconds set by the
CHANGE MASTER TOstatement (default 60) before attempting to reconnect.