On Nov 4, 2008, at 4:10 PM, Lenn0x wrote:
>
> Hi
>
> I have 2 sessions created:
>
> a_engine = create_engine('mysql:///host1', echo=True)
> a_session = scoped_session(sessionmaker(autoflush=True,
> transactional=True, bind=a_engine))
>
> b_engine = create_engine('mysql:///host2', echo=True)
> b_session = scoped_session(sessionmaker(autoflush=True,
> transactional=True, bind=b_engine))
>
> The issue I run into is, what happens when b_session's server crashes?
> I am looking at this from a high availability standpoint. I want to
> round-robin between 2 pools of persistent connetions. Both hosts share
> the same data. If b_session is down, don't use that session until its
> recovered.
>
> In my cases using a hardware vip would probably make this easier, but
> since we're dealing with persistent connections -- it makes it a tad
> more complex. I *could* create 1 pool thats connected directly to a
> hardware vip and let that round-robin through the DBs on the initial
> 'connect'. But if I start adding more servers that host my application
> I could run into a scenario of more connections living on A vs B and
> it becomes unpredictable. Managing 2 pools allows me to control X
> connections per host and adjust as I add more servers.
how is your own in-application round robining going to do a better job
than an existing load balancing solution , such as
http://dev.mysql.com/doc/refman/5.0/en/load-balancer.html
?
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