Keepalived
Keepalived Loadbalancer
Introduction
this page contains a basic description about how to set up keepalived for Open-Xchange cluster. This example is to work on debian systems. Keepalived mode is Direct Routing.
It is required to have ox servers and loadbalancer connected to the same switch or hub and that there is no filter for network packages between (some virtualization system do filter, too), so that MAC rewriting works.
For more information please see: www.keepalived.org
Software installation
Packages are installed using
test1:~# apt-get install keepalived
Keepalived requires some kernel modules to be loaded. They are loaded by the ipvsadmm service. So we enable it using dpkg-reconfigure:
dpkg-reconfigure ipvsadm
Answer the questions with "Yes" ("load ... at boot") and then "backup" for "Daemon method".
Enable IP forwarding on the keepalived node: configure in /etc/sysctl.conf:
net.ipv4.ip_forward=1
Enable this by either rebooting or by issuing sysctl -w net.ipv4.ip_forward=1.
Configuration example: HTTP
Keepalived configuration file
Create a file
/etc/keepalived/keepalived.conf
with following contend (adapt network adresses)
global_defs {
router_id OX
}
vrrp_sync_group OX_GROUP {
group {
OX_GOUP
}
}
vrrp_instance OX_VRRP {
state BACKUP
interface eth0
garp_master_delay 10
virtual_router_id 10
priority 101
nopreempt
advert_int 1
authentication {
auth_type AH # Simple 'PASS' can use
auth_pass 1234 # example password '1234'
}
virtual_ipaddress {
10.20.30.77/24 brd 10.20.30.255 dev eth0 # virtual service ip 10.20.30.67
}
virtual_ipaddress_excluded {
}
}
virtual_server_group OX_HTTP {
10.20.30.77 80 # virtual ip and port 80
}
virtual_server_group OX_OL_PUSH {
10.20.30.77 44335 # VIP VPORT
}
virtual_server group OX_HTTP {
delay_loop 3
lvs_sched rr
lvs_method DR
protocol TCP
virtualhost 10.20.30.77
real_server 10.20.30.123 80 {
weight 1
inhibit_on_failure
HTTP_GET {
url {
path /servlet/TestServlet
status_code 200
}
connect_port 80
connect_timeout 10
}
}
real_server 10.20.30.321 80 {
weight 1
inhibit_on_failure
HTTP_GET {
url {
path /servlet/TestServlet
status_code 200
}
connect_port 80
connect_timeout 10
}
}
}
virtual_server group OX_OL_PUSH {
delay_loop 3
lvs_sched rr
lvs_method DR
protocol UDP
real_server 10.20.30.123 44335 {
weight 1
inhibit_on_failure
TCP_CHECK {
connect_port 9999
connect_timeout 5
}
}
real_server 10.20.30.321 44335 {
weight 1
inhibit_on_failure
TCP_CHECK {
connect_port 9999
connect_timeout 5
}
}
}
Configuration example: Keepalived for Galera Loadbalancing
Keepalived configuration file
Here:
- loadbalancer IP
10.20.29.174 - Three galera nodes:
10.20.29.140,10.20.29.142,10.20.29.138
global_defs {
# This should be unique.
router_id galera-lb
}
vrrp_instance mysql_pool {
# The interface we listen on.
interface eth0
# The default state, one should be master, the others should be set to SLAVE.
state MASTER
priority 101
# This should be the same on all participating load balancers.
virtual_router_id 19
# Set the interface whose status to track to trigger a failover.
track_interface {
eth0
}
# Password for the loadbalancers to share.
authentication {
auth_type PASS
auth_pass Twagipmiv3
}
# This is the IP address that floats between the loadbalancers.
virtual_ipaddress {
10.20.29.174/32 dev eth0
}
}
# Here we add the virtal mysql node
virtual_server 10.20.29.174 3306 {
delay_loop 6
# Round robin, but you can use whatever fits your needs.
lb_algo rr
lb_kind DR
protocol TCP
# For each server add the following.
real_server 10.20.29.140 3306 {
weight 10
MISC_CHECK {
misc_path "/etc/keepalived/galera-checker.pl 10.20.29.140"
misc_timeout 5
}
}
real_server 10.20.29.142 3306 {
weight 11
MISC_CHECK {
misc_path "/etc/keepalived/galera-checker.pl 10.20.29.142"
misc_timeout 5
}
}
real_server 10.20.29.138 3306 {
weight 12
MISC_CHECK {
misc_path "/etc/keepalived/galera-checker.pl 10.20.29.138"
misc_timeout 5
}
}
}
Adding a second Keepalived node for redundancy
Set up a second Keepalived node as described above, with the following changes:
- Change the router_id (to the hostname, for example)
- Change the state to BACKUP
- Change the priority to something lower than the masters priority (e.g. 100)
Make sure the virtual_router_id and authentication information is the same on the backup keepalived node as on the master keepalived node.
Now the backup node will notice the master going down and take over. Automatic failback also happens.
Networking adjustments for the galera nodes
The galera nodes need the loadbalancer IP configured on some network device in order for galera to be able to bind on this device.
However, creating a fully configured "alias" device is bad, since the galera nodes will pick the loadbalancer IP as primary IP of the node for example for full state transfers (SST). So when trying a SST the galera nodes will try to connect to the loadbalancer on the SST port. This will fail because on the loadbalancer nothing listens on the SST port.
If we instead create a dummy device and only assign an IP to it (without setting all those flags like UP), then galera can bind to the IP, but it won't use the IP as its primary IP. A configuration like this can be created using the following trick. Ad dsome pre-up, post-up, pre-down, post-down lines to the /etc/network/interfaces file as follows:
allow-hotplug eth0
iface eth0 inet dhcp
pre-up echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore
pre-up echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce
post-up ip addr add 10.20.29.174/32 dev dummy0
pre-down ip addr del 10.20.29.174/32 dev dummy0
post-down echo 0 > /proc/sys/net/ipv4/conf/all/arp_ignore
post-down echo 0 > /proc/sys/net/ipv4/conf/all/arp_announce