Coyote Point Systems E350GX, Installation And Administration Manual

Page: 133 / 344

Configuring a Cluster’s Load-Balancing Options
Equalizer Installation and Administration Guide 133
The
once only
flag is enabled by default when adding an L7 cluster. In general, it is more efficient to enable
once
only
; but, in situations where load balancing decisions need to be made for every request or where any of the above
effects are undesirable,
once only
should be disabled.
Enabling Both the Once Only and Always Options
The
always
flag influences when Equalizer inserts cookies into server responses; it in turn is affected by the setting
of the
once only
flag, as shown in the following table:
Note that the cluster parameters
cookie path
,
cookie age
,
cookie generation
, and
cookie domain
specify cookie
content for the cluster (see “Layer 7 Persistence Tab” on page 116). If any of these parameters are updated, this
changes the information used in the cookies that Equalizer inserts into server responses.
Enabling Once Only and No Header Rewrite for HTTPS
In a Layer 7 HTTPS cluster, clients connect to the cluster IP using HTTPS connections. Equalizer terminates the
HTTPS connection and communicates with the servers in the cluster using the HTTP protocol. By default, Equalizer
examines server responses for
http://
URLs and rewrites them as
https://
URLs, so that these URLs work
Note – Although it is permitted by the software, it is not recommended to define a Layer 7 cluster with persist and
once only both turned off, and with no match rules. By defining a Layer 7 cluster in such a way, you are
essentially disabling Layer 7 processing, while still incurring extra overhead for the Layer 7 cluster. If your
application requires a cluster with no persistence, header processing, or match rules, then we recommend that
you define a Layer 4 UDP or TCP cluster for the best performance.
once only
enabled
once only
disabled
always enabled
Equalizer always inserts a cookie into
the
first set of response headers on a
connection only . The cookie is
inserted regardless of whether the
server included one in the response.
Subsequent responses on the same
connection are forwarded to the client
unchanged by Equalizer.
Equalizer inserts its own cookie into
all server responses on a
connection. The cookie is inserted
regardless of whether the server
included one in the response.
always disabled
If the first server response on a
connection already has a server
cookie in it, Equalizer inserts its own
cookie into the
first set of response
headers on the connection. If the
response has no cookie in it, Equalizer
does
not insert one of its own.
Subsequent responses on the same
connection are forwarded to the client
unchanged by Equalizer.
If the first server response on a
connection already has a server
cookie in it, Equalizer inserts its
own cookie into the
first set of
response headers on the
connection.
Equalizer will insert a cookie into
subsequent responses on the same
connection if:
• they do not contain a valid cookie
• the
cookie generation
has
changed
•
the server in the cookie has the
quiesce
flag enabled