Recently, I have observed the below statement in the master server's MySQL error log many number of times.
"started bin_log dump to slave server"
Exact message is this:
Start binlog_dump to slave_server
In the source code this string is saved in the logfile when this function is called:
With a bit of research, I see that just before this function is called, changes the slave state to this:
Requesting binlog dump and in the MySQL reference manual says that this state is set just when the slave connects with the master.
So, exactly, this message appears when the slave connects with the master.
So it seems that the slave loses connection with the master and then reconnects.