Control the Maximum speed(KB/s) to read binlog from master #269
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In some case, the speed of reading binlog from master is high, especially when doing a new replica.
It would bring the high traffic in master.
So We introduce a new variable "read_binlog_speed_limit" to control the binlog reading rate for IO thread to solve the problem.
handle_io_slave:
last_add_time = now()
tokens = read_binlog_speed_limit //there are some initial tokens in the bucket
while(true){
event = read_event()
if (read_binlog_speed_limit > 0) {
if (tokents > TOKEN_MAX) {
tokens = TOKEN_MAX
last_add_time = now()
}
do{
//put some token
tokens = tokens + (now()-last_add_time)*read_binlog_speed_limit;
//if the token is not enough, sleep some time.
if(tokens < event.real_network_read_len)
sleep((event.len-tokens)/speed_limit)
}
}
write_event(event)
}
It can work when slave_compressed_protocol is on.
But it maybe doesn't work well when the binlog event is very big.