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HI,
VRRP - virtual router redundancy protocol
Keepalived is software writeen by Alexandre Cassen (hope my spelling is
right). What is can do it as such:
1. Health checking of realserver allowing removing of unresponsive ones
from an lvs table (auto control of the lvs table)
2. Heartbeat between two lvs boxes so that if one fails the other
takesover.
So, with these two you can create a High Availibity (HA) cluster.
Using "2" only you can setup a service, like MySQL replication, and run
just the heartbeat (in this case VRRP framework) without the health
checking or LVS framework. Then if the master node goes down the slave
node can run a script to convert the slave database into a master
database.
So, if you have a master system say dbmast.ex.com, and a slave
dbslav.ex.com you create a service IP db.ex.com. All clients talk through
db.ex.com. On startup, dbmast.ex.com arps out gratuitously that it is
db.ex.com. On failure, dbslave.ex.com would arp out to take over the
systems.
This way, client need not know of any changes.
Go to www.keepalived.org for more info. If you have any further
questions, there is a mailing list, and I have helped in the past with the
documentation.
Ramon Kagan
York University, Computing and Network Services
Unix Team - Intermediate System Administrator
(416)736-2100 #20263
rkagan@xxxxxxxx
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I have not failed. I have just
found 10,000 ways that don't work.
- Thomas Edison
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On Thu, 15 Aug 2002, Doug Schasteen wrote:
> What does the keepalived vrrp do exactly? What are you using MySQL for?
> Because if you are running scripts or web programs, then don't you need
> to specify an IP in your connection strings? I'm just wondering how that
> works, because if all your connection strings are set to a certain IP
> and then that IP goes down, how does it know to fail over to the second
> machine? The only thing I can think of is your second machine takes over
> that IP somehow.
>
> I was planning on tackling this issue by writing (rewriting) all of my
> scripts/programs to include one file that does the mysql connections.
> Then I only have to change one file when I want to change where my mysql
> connections go. And then maybe I'll add a failover connection inside of
> that include file, like an "if the first connection didn't work, try the
> backup server". The problem with that is that if for some odd reason the
> first connection doesn't work (perhaps I rebooted the machine), it will
> put them on the backup server and updates will be made to the backup
> server. Any updates made to the backup mysql server while I'm rebooting
> the main mysql server will probably be lost. I can maybe add two-way
> replication for when something like this happens (but not use two-way
> replication all the time, because I've heard that has problems.)
>
> - Doug
>
>
>
>
> -----Original Message-----
> From: lvs-users-admin@xxxxxxxxxxxxxxxxxxxxxx
> [mailto:lvs-users-admin@xxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Ramon Kagan
> Sent: Thursday, August 15, 2002 7:43 AM
> To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
> Subject: Re: Survey: synchronisation and deployment
>
> For our MySQL setup I have a single "MySQL" machine. I setup my MySQL
> to
> listen on the designated port and have setup strict rules in MySQL for
> authentication and access. (see mysql.user and mysql.db tables). For
> redundancy I have a second machine running as a replication slave
> against
> the MySQL machine. I'm using keepalived's vrrp framework to force
> failover when problems arise (hasn't happened yet, knocking on wood
> really hard).
>
>
>
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>
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