On 10/28/2011 3:38 PM, jiangwen jiang wrote:
> Hi, all:
> I am confusing with seconds_behind_master, in mysql manual, it says:
> In essence, this field measures the time difference in seconds between the
> slave SQL thread and the slave I/O thread.
> how to understand this description:
> 1. seconds_behinds_master = ts in SQL thread - ts in I/O thread, or
> seconds_behinds_mater = ts in I/O thread - ts in SQL thead
> 2. how to get the timestamp in SQL and I/O thread, when this time will
According to <High performance mysql>,
seconds_behinds_master is inaccurate, so I just skipped how it works...
If you want to measure slave lag, follow that book's suggestion:
One good solution is a heartbeat record,which is a timestamp that you update once
persecond on the master.To calculate the lag,you can simply subtract the heartbeat from
the current timestamp on the slave.