Red Hat Cluster Suite, Руководство пользователя

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Chapter 7. Linux Virtual Server Overview 95
Once started, the
lvs
daemon calls the
ipvsadm
utility to configure and maintain the IPVS
routing table in the kernel and starts a
nanny
process for each configured virtual server on
each real server. Each
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.
7.6.1. Components of an LVS Cluster
Section 7.6.1.1
pulse
shows a detailed list of each software component in an LVS router.
7.6.1.1.
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.
7.6.1.2.
lvs
The
lvs
daemon runs on the active LVS router once called by
pulse
. It reads the configu-
ration 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.
7.6.1.3.
ipvsadm
This service updates the IPVS routing table in the kernel. The
lvs
daemon sets up and
administers an LVS cluster by calling
ipvsadm
to add, change, or delete entries in the
IPVS routing table.