Installation guide

nanny process checks the state of one configured service on one real server, and tells the lvs daemon

if the service on that real server is malfunctioning. If a malfunction is detected, the lvs daemon instructs

ipvsadm to remove that real server from the IPVS routing table.

If the backup router does not receive a response from the active router, it initiates failover by calling

send_arp to reassign all virtual IP addresses to the NIC hardware addresses (MAC address) of the

backup node, sends a command to the active router via both the public and private network interfaces to

shut down the lvs daemon on the active router, and starts the lvs daemon on the backup node to

accept requests for the configured virtual servers.

1.6.1. LVS Components

Section 1.6.1.1, “pulse” shows a detailed list of each software component in an LVS router.

1.6.1.1. pulse

This is the controlling process which starts all other daemons related to LVS routers. At boot time, the

daemon is started by the /etc/rc.d/init.d/pulse script. It then reads the configuration file

/etc/sysconfig/ha/lvs.cf. On the active router, pulse starts the LVS daemon. On the backup

router, pulse determines the health of the active router by executing a simple heartbeat at a user-

configurable interval. If the active router fails to respond after a user-configurable interval, it initiates

failover. During failover, pulse on the backup router instructs the pulse daemon on the active router to

shut down all LVS services, starts the send_arp program to reassign the floating IP addresses to the

backup router's MAC address, and starts the lvs daemon.

1.6.1.2. lvs

The lvs daemon runs on the active LVS router once called by pulse. It reads the configuration file

/etc/sysconfig/ha/lvs.cf, calls the ipvsadm utility to build and maintain the IPVS routing table,

and assigns a nanny process for each configured LVS service. If nanny reports a real server is down,

lvs instructs the ipvsadm utility to remove the real server from the IPVS routing table.

1.6.1.3. ipvsadm

This service updates the IPVS routing table in the kernel. T he lvs daemon sets up and administers LVS

by calling ipvsadm to add, change, or delete entries in the IPVS routing table.

1.6.1.4 . nanny

The nanny monitoring daemon runs on the active LVS router. T hrough this daemon, the active router

determines the health of each real server and, optionally, monitors its workload. A separate process

runs for each service defined on each real server.

1.6.1.5. /etc/sysconfig/ha/lvs.cf

This is the LVS configuration file. Directly or indirectly, all daemons get their configuration information

from this file.

1.6.1.6. Piranha Configuration Tool

This is the Web-based tool for monitoring, configuring, and administering LVS. This is the default tool to

maintain the /etc/sysconfig/ha/lvs.cf LVS configuration file.

1.6.1.7. send_arp

This program sends out ARP broadcasts when the floating IP address changes from one node to

another during failover.

Red Hat Enterprise Linux 4 Virtual Server Administration