HP e-Commerce / XML director server appliance sa8250 - Users Guide

C H A P T E R 2 HP e-Commerce/XML Director Server Appliance SA8250 User Guide

Sticky Persistence

For source-ip based sticky, the relationship between the client IP

address and the fulfillment server remains in effect for the entire time

the SA8250 is online or until the sticky timeout value expires. In the

event of failover, the sticky relationship is lost. Cookie sticky remains

in effect while the browser is running or until the sticky timeout value

expires. Since the browser maintains the cookie, cookie sticky is

maintained in the event of failover. The system clocks on both

SA8250s must be synchronized for failover handling to work. You do

this by enabling Network Time Protocol (NTP) using the Boot

Monitor. The administrator can control the length of time a server is

forced to handle serial requests from a single client using the sticky

timeout value.

Sticky-timeout

NOTE: All cookie sticky

RICH services will be

stuck to the same server

for the duration of the

sticky timeout value.

The SA8250 treats the timeout differently for cookie versus source-

ip sticky. With source-ip sticky, the timeout is reset with every

connection from the client (so that the timeout is effectively an "idle

time"). With cookie sticky, the timeout starts with the first

connection from the client to the server, and never gets reset. When

the cookie expires, even if actively being used, the next connection

will be load balanced to a new server.

We recommend that you set the cookie sticky timeout value to at least

1.5 times the maximum amount of time a user will expect to be stuck

to a server. If you are uncertain of the exact setting, we recommend

using 43200 seconds (12 hours) as the default.

SSL and Sticky

SSL (Secure Sockets Layer, or HTTPS) enabled services can also be

made sticky by specifying “sticky cookie” or “sticky src-ip” on the

CLI. For SSL services, sticky cookie behaves exactly as it does for

ordinary HTTP services. Source IP sticky uses the SSL session ID to

maintain server context. The server relationship will not survive

failover. As with sticky cookie, use of the session ID uniquely

identifies the client even if the request passes through a proxy server.