Yearly Archives: 2008

Stuff to check out for Linux SysAdmin clustering and scalability tools

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Puppet is an open-source next-generation server automation tool. It is composed of a declarative language for expressing system configuration, a client and server for distributing it, and a library for realizing the configuration.

The primary design goal of Puppet is that it have an expressive enough language backed by a powerful enough library that you can write your own server automation applications in just a few lines of code. With Puppet, you can express the configuration of your entire network in one program capable of realizing the configuration. The fact that Puppet has open source combined with how easily it can be extended means that you can add whatever functionality you think is missing and then contribute it back to the main project if you desire.
http://reductivelabs.com/trac/puppet

Hypertable is an open source project based on published best practices and our own experience in solving large-scale data-intensive tasks. Our goal is to bring the benefits of new levels of both performance and scale to many data-driven businesses who are currently limited by previous-generation platforms. Our goal is nothing less than that Hypertable become one of the world’s most massively parallel high performance database platforms.
http://www.hypertable.org/

KeepAlived as Load balancer with failover

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A setup for simple implementation of load balance of service, example ssh.
Two machines will be accepting SSH connections, and at the same time act as master/backup failover.

The two machines are connected to a local network and will be assigned a new virtual ip by keepalived.

Steps:
1. On the two debian/ubuntu machines, do

 $ sudo apt-get install keepalived

2. Copy the config for keepalived on the first machine:

First Server(Ubuntu Gutsy):
/etc/keepalived/keepalived.conf

global_defs {
 lvs_id LVS_MAIN
}

virtual_server 192.168.1.100 22 {
 delay_loop 30
 lb_algo wrr
 lb_kind NAT
 persistence_timeout 50
 protocol TCP
 #sorry_server 192.168.100.100 80
 real_server 192.168.1.50 22 {
 weight 2
 inhibit_on_failure
 TCP_CHECK {
 connect_port 22
 connect_timeout 3
 nb_get_retry 3
 delay_before_retry 1
 }
 }

 real_server 192.168.1.3 22 {
 weight 1
 inhibit_on_failure
 TCP_CHECK {
 connect_port 22
 connect_timeout 3
 nb_get_retry 3
 delay_before_retry 1
 }
 }
}

vrrp_instance VI_1 {
 state MASTER
 interface eth0
 virtual_router_id 1
 priority 100
 #authentication {
 #  auth_type PASS
 #  auth_pass
 #}
 virtual_ipaddress {
 192.168.1.100/24 brd 192.168.1.255 dev eth0
 }
}

3. Run the keepalived daemon by,

 $ sudo /etc/init.d/keepalived start

4. Check the IP address now loading:

 $ ip addr show eth0

5. Or via:

 $ sudo tail -f /var/log/messages

6. Now for the second server, Same copy of of the First Server conf but with changes below:
Second Server Configuration(Debian Etch):
/etc/keepalived/keepalived.conf

vrrp_instance VI_1 {
 state MASTER
 #interface eth1
 #CHANGES: it was in eth0 so,
 interface eth1

 virtual_router_id 1
 #CHANGES: it will be a backup, set priority to 100.
 priority 100

 virtual_ipaddress {
 #192.168.1.100/24 brd 192.168.1.255 dev eth1
 # CHANGES: it was in eth0,set as eth0
 192.168.1.100/24 brd 192.168.1.255 dev eth0
 }
}

7. Run keepadlived daemon:

 $ sudo /etc/init.d/keepalived start

8. Check the log files of the second server:

 $ sudo tail -f /var/log/messages

To test failover, disable the network interface at the first server:

 $ sudo /sbin/ifdown eth0

After disable the network interface at First Server, notice the resulting message in the log file showing the transition of the backup server as a master. When the master server is brought back, it automatically set back as backup.

Jun 15 12:30:31 debian Keepalived_healthcheckers: Using MII-BMSR NIC polling thread…
Jun 15 12:30:31 debian Keepalived_healthcheckers: Registering Kernel netlink reflector
Jun 15 12:30:31 debian Keepalived_healthcheckers: Registering Kernel netlink command channel
Jun 15 12:30:31 debian Keepalived_healthcheckers: Configuration is using : 10050 Bytes
Jun 15 12:30:31 debian Keepalived_healthcheckers: IPVS: Module is wrong version
Jun 15 12:30:31 debian last message repeated 2 times
Jun 15 12:30:31 debian Keepalived_healthcheckers: Activating healtchecker for service [192.168.1.50:22]
Jun 15 12:30:31 debian Keepalived_healthcheckers: Activating healtchecker for service [192.168.1.3:22]
Jun 15 12:30:31 debian Keepalived_vrrp: Using MII-BMSR NIC polling thread…
Jun 15 12:30:31 debian Keepalived_vrrp: Registering Kernel netlink reflector
Jun 15 12:30:31 debian Keepalived_vrrp: Registering Kernel netlink command channel
Jun 15 12:30:31 debian Keepalived_vrrp: Registering gratutious ARP shared channel
Jun 15 12:30:31 debian Keepalived_vrrp: Configuration is using : 33353 Bytes
Jun 15 12:30:32 debian Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATE
Jun 15 12:30:33 debian Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE
Jun 15 12:30:35 debian Keepalived_healthcheckers: TCP connection to [192.168.1.50:22] failed !!!
Jun 15 12:30:35 debian Keepalived_healthcheckers: Disabling service [192.168.1.50:22] from VS [192.168.1.100:22]
Jun 15 12:30:35 debian Keepalived_healthcheckers: IPVS: Module is wrong version
Jun 15 12:31:00 debian Keepalived_vrrp: VRRP_Instance(VI_1) Received higher prio advert
Jun 15 12:31:00 debian Keepalived_vrrp: VRRP_Instance(VI_1) Entering BACKUP STATE
Jun 15 12:31:05 debian Keepalived_healthcheckers: TCP connection to [192.168.1.50:22] success.
Jun 15 12:31:05 debian Keepalived_healthcheckers: Enabling service [192.168.1.50:22] to VS [192.168.1.100:22]

On my test, I got the error Module is wrong since the first server has ubuntu ipvsadm version 1.2.1 and the second server debian etch version 1.0.11. The setup works but hoping there would be any problem with the two different version. I still believe it’s good to have identical version for the ipvsadm for this setup.

The idea is clear enough where you can setup your web service to have a load balanced and failover capabilities.