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From Adrian Lewis <>
Subject RE: Examples of configuring DB HA?
Date Mon, 09 Jun 2014 22:18:27 GMT
I was very close to getting this up and running in the lab (Centos 6.5 – 2
x sql servers and 1 mgmt server – all running in VMware Workstation,
installed from 4.3 repo) but when setting the db.ha.enabled to true and
restarting the mgmt. server, I now get 404 from tomcat and the management
server log has lines in it saying things like:

2014-06-09 22:48:00,632 ERROR [c.c.u.d.Merovingian2] (main:null) Unable to
get a new db connection

java.sql.SQLException: Invalid load balancing strategy


Caused by: java.lang.ClassNotFoundException:

Anyone got any idea? Tried Googling and searching the mailing list but
nothing that I can see as an answer. I’m just a lowly network engineer so
wouldn’t know what these errors mean but I’m guessing I won’t be the first.

Any ideas?

*From:* Adrian Lewis []
*Sent:* 06 June 2014 10:51
*Subject:* Re: Examples of configuring DB HA?

Hi all,

Firstly thanks for the great responses already.

Secondly, regarding HA vs failover, I had been assuming these as much the
same. Based on what I had read about the new changes in 4.3, I had assumed
that the new feature allows you to configure standard MySQL (clustering not
required - Galera or otherwise) in a multimaster replication setup and that
while management servers only speak with a single server at a time,
failover to a backup server is automatic and does not need any work on the
MySQL side to promote a slave to a master as with a basic master/slave

I'm personally not interested in load balancing just yet, simply having a
hot standby DB that takes over automatically. This is what I take the term
HA to mean.

>From the wiki, I'm also taking it that the use of the auto increment and
offset values ensure that the two DBs can safely run as master-master in
the event that each gets written to concurrently (split brain or just two
mgmt servers failing over at slightly different times).

It seems that this thread is already highlighting some of the confusion I
and others have faced. Hopefully it will help someone else.

Thanks again,


On 6 Jun 2014 07:18, "Shanker Balan" <> wrote:

Hi Damodar,

Comments inline.

On 06-Jun-2014, at 10:53 am, Damoder Reddy <> wrote:

> Hi Adrian,
> For your question, . Is the CS side purely for failover or does it
actually set up part of the replication for you? The answer is, the Cloud
Stack does only failover configuration and the actual replication process
on the mysql side has to be done by own.

> For the second question, Can you easily enable an existing DB for HA or
is this best done before there’s any data? The answer is, we can setup
replication even with existing data and then start the management servers.
The mysql documentation contains the clear steps how to setup replication
with existing documentation. Probably that is the reason why we might not
have included these steps in the doc.

The OP is looking for HA, not failover. HA is possible in ACS 4.3.0
using MySQL Clustering.

Once you have MySQL Clustering, its multi-master and not one master to many
ACS should not fence itself like it currently does when the master is not

> The configuraiton we need to do on each management server is as below.
> You can follow the design doc steps if you think there is a minimal
documentation in the 4.3 doc. The design doc also contains the links to
mysql site for setting up the replication for fresh as well as existing
> From the cloud stack side it is purely failover and falling back between
the IPs configured for the master/salve databases.

> -----Original Message-----
> From: Adrian Lewis []
> Sent: Friday, June 6, 2014 6:46 AM
> To:
> Subject: Examples of configuring DB HA?
> Hi all,
> Does anyone have any example configs or blog posts explaining the DB HA
features introduced in 4.3? Between the section in the design docs on the
wiki and the official docs, I’m a little confused as to how it’s supposed
to be set up – they appear to differ although there’s a lot more detail in
the design docs. Some of it is clearly MySQL stuff that’s outside of
Cloudstack but some of it is Cloudstack config as well. I’m just trying to
get a feel for what is the best way to use what’s made it into 4.3 final
(if different to the design docs). I’m not too strong on MySQL so I can’t
easily work out what’s a requirement, what’s just recommended (and
> implications) and what the Cloudstack side actually does. Is the CS side
purely for failover or does it actually set up part of the replication for
you? Can you easily enable an existing DB for HA or is this best done
before there’s any data? Before you run cloudstack-setup-databases?
> Shanker – I don’t suppose this subject could add to your already
excellent blog post collection?
> Thanks in advance,
> Adrian


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