This chapter contains instructions for configuring Red Hat Enterprise Linux to make
the Apache HTTP Server highly available.
The following is an example of setting up a cluster service that fails
over an Apache HTTP Server. Although the actual variables used in the service depend
on the specific configuration, the example may assist in setting up a
service for a particular environment.
First, configure Apache HTTP Server on all nodes in the cluster. If using a
failover domain , assign the service to all cluster nodes configured to
run the Apache HTTP Server. Refer to Section 3.6 Configuring a Failover Domain for
instructions. The cluster software ensures that only one cluster system
runs the Apache HTTP Server at one time. The example configuration consists of
installing the httpd RPM package on all cluster
nodes (or on nodes in the failover domain, if used) and configuring a
shared GFS shared resource for the Web content.
When installing the Apache HTTP Server on the cluster systems, run the
following command to ensure that the cluster nodes do not automatically
start the service when the system boots:
Rather than having the system init scripts spawn the
httpd daemon, the cluster infrastructure initializes
the service on the active cluster node. This ensures that the
corresponding IP address and file system mounts are active on only one
cluster node at a time.
When adding an httpd service, a
floating IP address must be assigned to the
service so that the IP address will transfer from one cluster node to
another in the event of failover or service relocation. The cluster
infrastructure binds this IP address to the network interface on the
cluster system that is currently running the Apache HTTP Server. This IP address
ensures that the cluster node running httpd is
transparent to the clients accessing the service.
The file systems that contain the Web content cannot be
automatically mounted on the shared storage resource when the cluster
nodes boot. Instead, the cluster software must mount and unmount the
file system as the httpd service is started and
stopped. This prevents the cluster systems from accessing the same data
simultaneously, which may result in data corruption. Therefore, do not
include the file systems in the /etc/fstab
file.
