On Mon, 25 Jan 2010 11:51:24 -0800, Jeremy Zawodny <jer...@zawodny.com> wrote: > On Mon, Jan 25, 2010 at 11:47 AM, Alex Yurchenko < > alexey.yurche...@codership.com> wrote: > >> On Mon, 25 Jan 2010 10:47:23 -0800, Jeremy Zawodny <jer...@zawodny.com> >> wrote: >> > If the connection between a slave and master is interrupted, the slave >> > won't >> > report itself as being "behind" until the slave's network timeout to >> > the >> > master expires and it reconnect (assuming it can). >> > >> > Jeremy >> >> Hi Jeremy, >> >> Does it mean that you want to detect network outages using the heartbeat? >> If so, won't it be easier to just set master-slave connection timeout to >> the desirable value and let replication system to handle it? I'm asking >> this not from position of improving current replication in short term, >> but >> from position of whether a heartbeat function is needed in replication >> API? >> > > Not at all. > > My point is that you cannot (today) rely on MySQL slaves to "self report" > in > all situations. With a heatbeat that the master sends every N seconds and > the slave expects to see every N seconds, it's possible to see latency in > the replication stream regardless of the cause--even during weird network > outages that the slave won't notice until the timeout is reached. > > Does that make more sense? > Perhaps, but not for me really ;). Actually I still don't understand what exactly people mean by "heartbeat" here. According to http://dev.mysql.com/doc/refman/5.5/en/change-master-to.html it is simply a transport keepalive. It does not even measure latency. To me it is not a "feature" actually, it is a bugfix.
I realize that you are looking for solution to the present day situation. What I'm trying to figure out is whether it should be a part of replication API. So let me ask it differently. Suppose you have a replication system that provides cluster membership service (members come and gone) and provides you with a latency measurement (averaged over a specified window). Would you still need an explicit heartbeat "feature"? Regards, Alex -- Alexey Yurchenko, Codership Oy, www.codership.com Skype: alexey.yurchenko, Phone: +358-400-516-011 _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : maria-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
