Setting Up a High Availibility Service With Vip and Heartbeat | skybert.net

Setting Up a High Availibility Service With Vip and Heartbeat


Objective

We've got two hosts on the same network, wind (.108) and fire (.109) and they are to provide the VIP .200, which again relates to a crucial service which users only relate to by the host name of the VIP.

This VIP should at all times answer to requests, directing the traffic to wind normally, but in case wind is down, fire should take over automatically and answer to requests to the VIP.

Before we start

I used Debian Wheezy (testing at the time of writing) for setting this up. It should be pretty straight shooting to follow this guide on Debian based systems, such as Ubuntu too.

Start by setting up wind, then replicate the configuration to fire.

We don't need a CRM such as Pacemaker as Heartbeat is more than capable handling two nodes providing a service. If we'd needed three or more nodes providing one VIP or service, Pacemaker is the most used companion to heartbeat (previously called the crm module, now the directive is called pacemaker as it's diverged into its own project).

/etc/hosts

All hosts must know about each other by the node name, so wind has:

192.168.1.109 fire

and fire has:

192.168.1.108 wind

kernel tweaking

Add this to your /etc/sysctl.conf:

# needed to bind to VIP
net.ipv4.ip_nonlocal_bind=1

Load this with sysctl -p and make it persistent by running it at boot time, such as from /etc/rc.local

install heart beat

 # apt-get install heartbeat

/etc/ha.d/authkeys

# ( echo -ne "auth 1\n1 sha1 "; \
dd if=/dev/urandom bs=512 count=1 | openssl md5 ) \
> /etc/ha.d/authkeys
# chmod 0600 /etc/ha.d/authkeys

/etc/ha.d/ha.cf

###############################
# logging
debugfile /var/log/ha-debug

###############################
# communication
autojoin none
udpport 694
# the other node
ucast eth0 192.168.1.109
udp eth0

###############################
# thresholds
warntime 5
deadtime 15
initdead 60
keepalive 2

###############################
# nodes
node wind
node fire

## /etc/ha.d/haresources

# <primary node> <virtual IP (VIP)>
wind 192.168.1.200>

Propagate the settings to fire

$ /usr/share/heartbeat/ha_propagate

Watch out, the path on Debian differs from the official HA Proxy guide

Be sure to look over ha.cf, change the reference to the other node and confirm that the interface name is the same as on wind.

Read, set, go!

Now, you should be ready to try it out.

$ ssh root@wind
# /etc/init.d/heartbeat restart

wind should have bound the VIP to itself now as we've defined it to be the master node:

$ ifconfig eth0:0

Then, go to fire and restart heartbeat there too. Once you've done that, go back to wind and stop the network.

$ ssh wind
$ /etc/init.d/networking stop

Then switch to fire and confirm that it has "stolen" the VIP:

$ ssh fire
$ ifconfig eth0:0

Last step now, is to bring wind up again and see that it re-acclaims the VIP.

Congrats, you've just set up a high availability solution with VIPs! All clients can now safely relate to the VIP instead of the actual IP of any server providing the service.


gmail torstein.k.johansen @ gmail ~ twitter @torsteinkrause ~