KeepAlive menggunakan metode Direct Routing

November 25th, 2015

Saat ini saya ada project untuk konfigurasi Load Balancer dengan metode Direct Routing, atau yang biasa dikenal dengan DSR (Direct Server Return). Atau gambaran topologinya seperti ini.

IP Address	Status	Hostname
	vIP	LVS + LB
192.168.100.20	vIP	WS1
	vIP	WS2
	vIP	WSx
192.168.100.2	rIP	LVS + LB
192.168.100.3	rIP	WS1
192.168.100.4	rIP	WS2
192.168.100.5	rIP	WSx

Testbed kali ini saya menggunakan Cent OS 7, kebutuhannya packages-nya adalah keepalived.

root> yum install -y keepalived

Konfigurasi yang saya gunakan adalah sebagai berikut :

Silakan disesuaikan dengan kebutuhan pada saat deployment, terutama pada <public_ip_vip>, <pub_interface_handle_rip_vip> dan <public_real_ip_address>.

Setelah perubahan selesai dilakukan, silakan start keepalived.

root> systemctl start keepalived

Ketika keepalived sudah running dengan normal, seharusnya pada log muncul notifikasi seperti ini:

Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived[15916]: Starting Keepalived v1.2.13 (03/06,2015)
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived[15916]: Remove a zombie pid file /var/run/keepalived.pid
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived[15916]: Remove a zombie pid file /var/run/vrrp.pid
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived[15916]: Remove a zombie pid file /var/run/checkers.pid
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived[15917]: Starting Healthcheck child process, pid=15918
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Initializing ipvs 2.6
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived[15917]: Starting VRRP child process, pid=15919
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Netlink reflector reports IP 192.168.100.20 added
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Netlink reflector reports IP 192.168.100.2 added
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: Netlink reflector reports IP 192.168.100.20 added
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: Netlink reflector reports IP 192.168.100.2 added
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Registering Kernel netlink reflector
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: Registering Kernel netlink reflector
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Registering Kernel netlink command channel
Nov 26 00:21:08 loadbalancer.xtremenitro.org systemd[1]: Started LVS and VRRP High Availability Monitor.
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: Registering Kernel netlink command channel
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: Registering gratuitous ARP shared channel
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Opening file '/etc/keepalived/keepalived.conf'.
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Configuration is using : 16131 Bytes
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: IPVS: Service already exists
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: IPVS: Destination already exists
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Using LinkWatch kernel netlink reflector...
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Activating healthchecker for service [192.168.100.3]:80
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_healthcheckers[15918]: Activating healthchecker for service [192.168.100.4]:80
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: Opening file '/etc/keepalived/keepalived.conf'.
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: Configuration is using : 62447 Bytes
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: Using LinkWatch kernel netlink reflector...
Nov 26 00:21:08 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: VRRP sockpool: [ifindex(2), proto(112), unicast(0), fd(10,11)]
Nov 26 00:21:09 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: VRRP_Instance(LB_1) Transition to MASTER STATE
Nov 26 00:21:10 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: VRRP_Instance(LB_1) Entering MASTER STATE
Nov 26 00:21:10 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: VRRP_Instance(LB_1) setting protocol VIPs.
Nov 26 00:21:10 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: VRRP_Instance(LB_1) Sending gratuitous ARPs on enp5s0f0 for 192.168.100.20
Nov 26 00:21:15 loadbalancer.xtremenitro.org Keepalived_vrrp[15919]: VRRP_Instance(LB_1) Sending gratuitous ARPs on enp5s0f0 for 192.168.100.20

Silakan tambahkan parameter net.ipv4.ip_nonlocal_bind dengan nilai 1 pada sysctl.

Real Server

Kernel Tuning

Kernel tuning untuk ignore arp di sisi webserver, karena kita akan pakai interface loopback, maka kita akan setup individual arp ignore parameter di interface tersebut.

root> vim /usr/lib/sysctl.d/90-arp.conf
net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.lo.arp_announce = 2
net.ipv4.conf.all.arp_announce = 2

Tambahkan vIP pada loopback interface di masing-masing real server.

root> ifconfig lo:0 192.168.100.20 netmask 255.255.255.255

Interface Configuration

Supaya interface tersebut berjalan pada saat mesin di boot-up, maka tambahkan file pada /etc/sysconfig/network-scripts/ifcfg-lo:0, isinya sebagai berikut :

DEVICE=lo:0
IPADDR=192.168.100.20
NETMASK=255.255.255.255
ONBOOT=yes
NAME=loopback

Restart network service untuk memastikan script tersebut berjalan dengan normal.

root> systemctl restart network.service

Dari konfigurasi di atas, ada beberapa pro dan kontra mengenai metode Direct Routing atau DSR ini. Seperti yang di tuliskan oleh Big-IP, akan ada effort lebih untuk melakukan maintenance backend, karena load balancer di sini hanya bertugas untuk melemparkan traffic, bukan melakukan terminasi traffic.

Pros

Very low budget
No need big / huge load balancer

Cons

Security issue will be more complex
Cache optimization will be more complex since we must optimized all backend individually.

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Dewangga Alam

Father, Husband, and an Engineer!