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#1 (**permalink**) 02-28-2008, 10:01 AM

Hello

I m a bit new with mysql.
i want to use master/slave replication with mysql to implement load
balancing.
i can redirect the write to the master and use one of the slave for the
read.

but how the read after write should be implemented ?
for exemple:
-you are searching in a list of item (on a slave)
-you modify an item (on a master)
-you refresh the item list:
as it is a read request, it should be redirected to the slave
but is the slave sync'ed with master now ?
if not, the user will not see his update and he can think that he has to
modify again the item.

what is the best way to handle this case :
- refreshing from master after modif ?
- waiting than the slave is sync'ed ?
- other ?

#2 (**permalink**) 02-28-2008, 10:01 AM

patrice wrote:
> Hello
>
> I m a bit new with mysql.
> i want to use master/slave replication with mysql to implement load
> balancing.
> i can redirect the write to the master and use one of the slave for the
> read.
>
> but how the read after write should be implemented ?
> for exemple:
> -you are searching in a list of item (on a slave)
> -you modify an item (on a master)
> -you refresh the item list:
> as it is a read request, it should be redirected to the slave
> but is the slave sync'ed with master now ?
> if not, the user will not see his update and he can think that he has to
> modify again the item.
>
> what is the best way to handle this case :
> - refreshing from master after modif ?
> - waiting than the slave is sync'ed ?
> - other ?
>
>
>
mysql replication is designed to be almost synchronous. i suggest that
you run this command

SHOW SLAVE STATUS\G

on your master server, then look at the parameter seconds_behind_master.
it should be close to zero if you have a good network.

#3 (**permalink**) 02-28-2008, 10:01 AM

"lark" <hamzee@sbcdeglobalspam.net> a écrit dans le message de
news:_QTbi.3695$bP5.2881@newssvr19.news.prodigy.ne t...
> mysql replication is designed to be almost synchronous. i suggest that
> you run this command
>
> SHOW SLAVE STATUS\G
>
> on your master server, then look at the parameter seconds_behind_master.
> it should be close to zero if you have a good network.

thank you for the answer.
i ve effectively noticed that the slave is quickly updated.
but i guess it can exists some situation where the slave is not updated
immediatly (if multiple write are already pending)

so maybe i have to record a counter for each table in a special table,
inc'it at each update, and wait
(with a timeout the user can cancel) until the counter on the slave is >=
before resending the query from the slave.

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