Coyote Point Systems Equalizer GX Series, Administration Manual

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Working with Clusters and Match Rules
Match Rule Expressions
Match rules consists of a match expression and a match body, which identifies the operations to
perform if the expression is satisfied by the request. Match syntax is as follows:
match name {expression} then {body}
Each match has a name, which is simply a label. The name must follow the same restrictions as
those for cluster names and server pool names. All match names within a cluster must be unique.
Match expressions affect the subsequent processing of the request stream using URI, host, or
other information. They are made up of match functions, most of which are protocol-specific,
joined by logical operators, optionally preceded by the negation operator, with sets of beginning
and end parentheses for grouping where required. This may sound complex, and it can be, but
typical match expressions are simple; it is usually best from a performance perspective to keep
them simple.
The most simple match expression is one made up solely of a single match function. The truth
value (
true or false ) of this expression is then returned by the match function. For example, a
match function common to all Layer 7 protocols is the
any ()
function, which always returns true ,
independent of the contents of the request data. So, the most simple match expression is:
any()
which will always result in the match rule being selected.
Use the logical NOT operator to invert the sense of the truth value of the expression. So, you can
use the NOT operator to logically invert a match expression, as follows:
!expression
giving rise to the next simplest example:
!any()
which always evaluates to false and always results in the match rule not being selected.
With the addition of the logical OR (||) and logical AND (&&) operators, you can specify complex
expressions, selecting precise attributes from the request, as in this:
!happy() || (round() && happy())
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