PolyServe Understudy 1.3
4. Adding, Deleting and Updating Virtual Hosts
To add a virtual host to the cluster, choose the Add Virtual Host
option from the Cluster menu. Understudy will then open an
Add a Virtual Host dialog box. Enter the IP address or name of
the virtual host you wish to protect in the Virtual Host
field. Then you will need to choose which cluster server should be
primary for that virtual host, and which server would be backup, by
clicking on the corresponding check buttons. Finally, you need to
click on the OK button to authorize, or Cancel to cancel.
- Note:
- The server you choose to be primary for the new virtual host
is the one to which requests will be routed in the normal
case, i.e., when there are no failures.
- Note:
- Adding a virtual host will automatically configure its IP
address on the corresponding cluster servers. There is no
need to configure that IP address with other network utilities.
In particular, DO NOT configure this IP address in the setup
files of your web server.
- Note:
- Understudy does not take care of merging updates that were
received at the backup server with those that were received
at the primary, or of maintaining shared session variables.
This can be done by using external software.
To delete a virtual host from the cluster, first select the virtual
host you wish to delete by pointing the mouse on it and
clicking on the mouse left button. After the virtual host is
selected, choose Delete Selected Virtual Host from the
Cluster menu.
Understudy will then open an authorization dialog box. Click
yes if you wish to authorize the operation, or no if you
wish to cancel.
- Note:
- Deleting a virtual host will delete it and the corresponding
IP address from all servers in the cluster. In this version of
Understudy, a virtual host cannot be deleted from just one server.
To update a virtual host, first select the virtual host you wish to
update by pointing the mouse on it and clicking on the mouse left
button. After the virtual host is selected, choose Update Selected Virtual
Host
from the Cluster menu. Understudy will then open a dialog box
in which you can pick which cluster server should be primary for
that virtual host, and which should be backup. Clicking on the
corresponding check button to activate the desired configuration,
and then click OK to authorize, or Cancel to cancel.
- Note:
- If you wish to bring down a server for scheduled maintenance,
it is advisable (but not necessary) to first configure the
cluster so that this server is a backup for all virtual hosts.
This can be done by updating all configured virtual hosts before
taking the server down. Doing so will save the failure detection
time (approximately 10 seconds), and will ensure that your
clients receive seamless service from your web server.