Alteon Application Switch Operating System Application Guide
Health Checking
Document ID: RDWR-ALOS-V2900_AG1302
495
Script-Based Health Checks
Health check scripts dynamically verify application and content availability by executing a sequence
of tests based on send and expect commands.
This section includes the following topics:
•
Configuring Script-Based Health Checks, page 495
•
•
•
Scripting Guidelines, page 498
•
Script Configuration Examples, page 498
Configuring Script-Based Health Checks
You can configure Alteon to send a series of health check requests to real servers or real server
groups and monitor the responses. Both ASCII and binary-based scripts, for TCP and UDP protocols,
can be used to verify application and content availability.
The benefits of using script-based health checks include:
•
Ability to send multiple commands
•
Check for any return ASCII string or binary pattern
•
Test availability of different applications
•
Test availability of multiple domains or Web sites
Alteon supports the following capacity:
•
6K bytes per script
•
256 scripts per Alteon
A simple CLI controls the addition and deletion of commands to each script. New commands are
added and removed from the end of the script. Commands exist to open a connection to a specific
TCP or UDP port, send a request to the server, expect an ASCII string or binary pattern, and, for
TCP-based health checks only, to close a connection. The string or pattern configured with an
expect (or in the case of binary, bexpect) command is searched for in each response packet. If it is
not seen anywhere in any response packet before the real server health check interval expires, the
server does not pass the expect (or bexpect) step and fails the health check. A script can contain
any number of these commands, up to the allowable number of characters that a script supports.
Notes
•
Health check scripts can only be set up via the CLI, but once entered, can be assigned as the
health-check method using SNMP or the BBI.
•
There is no need to use double slashes when configuring a script in the BBI that uses special
characters with single slashes. For example, the script entry GET /index.html
HTTP/1.1\r\nHOST:www.hostname.com\r\n\r\n does not require the use of \\r or \\n
to ensure proper functioning of the script.
•
Only one protocol can be configured per script.
Script Formats
Health check script formats use different commands based on whether the content to be sent is
ASCII-based or binary-based. The close command is used only to close a TCP connection and is not
required if health checking a UDP-based protocol.
Each script should start with the command
open
<protocol port number>,
<protocol-name>
. The next line can be either a send or expect (for ASCII-based), or bsend or
bexpect (binary-based).
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