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132 Chapter 10. Configuring the LVS Routers with Piranha Configuration Tool
The following is a sample script to use as a guide when composing an external service-
checking script:
#!/bin/sh
TEST=‘dig -t soa example.com @$1 | grep -c dns.example.com
if [ $TEST != "1" ]; then
echo "OK
else
echo "FAIL"
fi
Note
If an external program is entered in the Sending Program field, then the Send field
is ignored.
Send
Enter a string for the
nanny
daemon to send to each real server in this field. By
default the send field is completed for HTTP. You can alter this value depending on
your needs. If you leave this field blank, the
nanny
daemon attempts to open the port
and assume the service is running if it succeeds.
Only one send sequence is allowed in this field, and it can only contain printable,
ASCII characters as well as the following escape characters:
•
\n for new line.
•
\r for carriage return.
•
\t for tab.
•
\ to escape the next character which follows it.
Expect
Enter a the textual response the server should return if it is functioning properly. If
you wrote your own sending program, enter the response you told it to send if it was
successful.
Tip
To determine what to send for a given service, you can open a
telnet
connection
to the port on a real server and see what is returned. For instance, FTP reports 220
upon connecting, so could enter
quit
in the
Send
field and
220
in the
Expect
field.