Coyote Point Systems Equalizer GX Series, Administration Manual

Page: 374 / 866

Working with Clusters and Match Rules
Whether
once only
is enabled or not has a significant effect on how Equalizer routes requests, as
summarized in the following table:
Requests
in a single
keep-alive
connection
once only enabled once only disabled
First Request
persist
enabled
If request contains a cookie and there is no
match rule hit, send request to the server in
the cookie.
If request contains a cookie and there is a
match rule hit, send the request to the server
in the cookie
only if it is in the list of servers
selected in the match rule definition .
Otherwise, ignore the cookie.
If there is no cookie, load balance the request
and send to the server chosen.
If request contains a cookie and there is no
match rule hit, send request to the server in
the cookie.
If request contains a cookie and there is a
match rule hit, send the request to the server
in the cookie
only if it is in the list of servers
selected in the match rule definition .
Otherwise, ignore the cookie.
If there is no cookie, load balance the request
and send to the server chosen.
persist
disabled
Load balance the request and send to the
server chosen. Load balance the request and send to the
server chosen.
match rule
hit
Send to the server chosen by the match rule. Send to the server chosen by the match rule.
Subsequent Requests
persist
enabled
Send to same server as first request (any
cookie in request is ignored).
If request contains a cookie, send request to
the server in the cookie.
If there is no cookie, load balance request and
send to server chosen by policy.
persist
disabled
Send to same server as first request.
Load balance the request and send to the
server chosen.
match rule
hit
Send to same server as first request. Send to the server chosen by the match rule.
For example, let’s look at how Equalizer processes HTTPS requests. For an HTTPS cluster,
Equalizer off loads SSL processing from the server pool in the cluster; that is, Equalizer does all
the SSL related processing itself, and then forwards the request in HTTP to the server. When it
does this, it inserts special headers into the request to indicate that the request was received by
Equalizer in HTTPS and processed into HTTP (see
"HTTPS Header Injection"
on page 380). If
once only
is set, these special headers are only inserted into the first request in a connection; the remainder
of the requests in the connection are still processed, but no headers are inserted. Most servers
that support SSL off loading require that every request contain the special headers -- therefore, in
most cases like this you need to disable the
once only
flag for the cluster if you want to be able to
parse for these headers in every request on the server end.
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.
374 Copyright © 2014 Coyote Point Systems, A Subsidiary of Fortinet, Inc.