MMM over WAN
Scott
masters on two geographically separated sites.
When connectivity is up between the sites, I want both sites to use
the same master. However, if connectivity goes down, both sites need
to go to the local server at their site.
Has anyone considered this type of implementation with MMM. Out of
the box, I don't think MMM would be suitable. The monitoring service
needs to reside at one of the sites, and if/when connectivity goes
down, the monitoring service wouldn't be able to communicate to the
other site to inform it of the virtual IP change. Does anyone have
any ideas (and/or tricks) of how MMM could be used to work in this
type of environment?
Cheers, Scott
Will G.
impossible to float between sites. If both sites are maintained by the
same provider and share an IP space, that should work, however, the
company I work for does not share VLANs or IP blocks between datacenter
locations. It is impossible to broadcast BGP for an IP if this is the
case. This would make it impossible to float the IP from one location
to the other.
Now, if that's not an issue, MMM would work if it was installed on
whatever device is connecting to these database servers. If you have
the servers in 2 locations and are concerned about their availability, I
would assume that your front end is in a third location. In this case,
run the monitor on this server, which will be able to detect just fine
when one of the servers goes down, due to a server issue or a site issue.
Regards, Will G.
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Arjen Lentz
Floating IP won't work in such a setup.
You'd have to use DNS (MMM2 supports that) or hosts based (OQ has been
working on that, we'll release it back).
However, you may just want to use a tool like HAproxy to deal with this.
OQ has some dual masters in different data centres, and uses HAproxy
for that.
Cheers,
Arjen.
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Justin Brehm
Like the others have said, it doesn't seem like something MMM would do
"out of the box". I'm just brainstorming here, but maybe using
something like MySQL proxy locally at both sites, having it do some
host checking and if the master is available, read from it, otherwise,
read from next in line. Another possible solution (and something I've
never really used) is that Continuent product. They have bunch of WAN
bullet points in their marketing material, it might not hurt to look.
One thing, and I'm sure you've probably already thought about this, if
the connection is broken and you have to suddenly begin using two
master servers in different locations, what happens when the
connection returns and you now have two sets of "master" data? I'm
seriously interested in what you might do here.
--
Justin Brehm
Scott
the mysql proxy approach. With mysql proxy, you would technically
still have a single point of failure (the proxy server). However, you
could easily make that service redundant with something like HA Linux
Following up to Justin's comment on "two sets of master
data"......yes, that is a very valid point. In my case, the systems
"should" have mutually exclusive data sets during an outage, meaning
that a re-sync "should" just work.....
Baron Schwartz
> Following up to Justin's comment on "two sets of master
> data"......yes, that is a very valid point. In my case, the systems
> "should" have mutually exclusive data sets during an outage, meaning
> that a re-sync "should" just work.....
I can't remember exactly when, but I think I've seen that work OK. I
know I have seen it fail a lot, and I can definitely remember those.
It would be worth testing.
Baron