Setting up Keepalived for System-level HA

tested on slackware current (oct 2021) and debian12

THTTPD / HAPROXY / whatever runs on every node

for the second and third use-cases we need to identify the nodes

#sbopkg -i thttpd
wget https://lab.nethence.com/slackpkgs/2021-10/thttpd-2.29-x86_64-1_SBo.tgz
installpkg --terse thttpd-2.29-x86_64-1_SBo.tgz
echo '<p>hello this is node1' > /var/www/thttpd/index.html
echo '<p>hello this is node2' > /var/www/thttpd/index.html
echo '<p>hello this is node3' > /var/www/thttpd/index.html

we’re enabling the check script only and we should avoid being contra-productive here, the restriction needs to be as light as possible, as with pidof.

vrrp_script checkacme {
        script "/sbin/pidof thttpd"
        #weight 50
        interval 1
        fall 2
        rise 1
}

vrrp_instance ACME {
        state BACKUP
        interface xenbr0
        virtual_router_id 51
        priority 1
        advert_int 1
        virtual_ipaddress {
                10.0.0.209/24
        }
        track_script {
                checkacme
        }
    notify "/var/tmp/notify.bash"
}

Highly-available outbound MTA

see postfix-relay-ha

Ready to go

back to the main guide

Additional notes

we use the overall notify script only to check about the various states, and prefer to use specific notify_state definitions instead.

    vi /var/tmp/notify.bash

    #!/bin/bash

    echo `date` -- $HOSTNAME received $@ >> /var/tmp/keepalive.log

    chmod +x /var/tmp/notify.bash

Resources

Setting up Keepalived for System-level HA

THTTPD / HAPROXY / whatever runs on every node

Highly-available outbound MTA

Ready to go

Additional notes

Resources

check & notify

tcp check

squid HA with check script

nginx HA with check script