Coyote Point Systems E350GX, Руководство по установке и администрированию

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General Match Expressions and Match Bodies
Equalizer Installation and Administration Guide 211
General Match Expressions and Match Bodies
A match rule 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 names. All match names within a cluster must be unique.
Match Expressions
Match expressions affect the subsequent processing of the request stream using URI, host, or other information.
Match expressions 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, (sometimes), 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:
NOT expression
giving rise to the next simplest example:
NOT 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:
NOT happy() || (round() && happy())
Match expressions are read from left to right. Expressions contained within parentheses get evaluated before other
parts of the expression. The previous expression would match anything that was not happy or that was round and
happy.
Unlike the previous example, match functions correspond to certain attributes in a request header.
For example, a request URI for a web page might look like this:
Get /somedir/somepage.html http/1.1
Accept: text/html, text/*, *.*
Accept-Encoding: gzip
Host: www.coyotepoint.com
User-Agent: Mozilla/4.7 [en] (Win98; U)
Note – The the logical negation operator is displayed as “NOT”, rather than “!”.