Coyote Point Systems Equalizer Spezifikationen PDF herunterladen (Seite 306)

Clusters

Requests

in a single

keep-alive

connection

once only enabled once only disabled

hit, send the request to the server in the cookie

onlyif

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.

hit, send the request to the server in the cookie

onlyif

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

Insertion” on page 139). 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.

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.

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:

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