Coyote Point Systems Equalizer Especificaciones descargar pdf (Pagina 330)

Match Rules

If we instead were to skip a match rule because, for example, the server selected by the match rule is down, the

request would be evaluated by the next match rule -- or the default match rule. The request, therefore, could

potentially be sent to a server in the cluster that does not have the requested content. This means that the client

would receive a “not found” error, instead of an error indicating that the appropriate server is not currently available.

Considering Case in String Comparisons

String comparisons performed by match functions honor the setting of the ignore case cluster parameter: if it is

set on the cluster (the default), then all match rule functions used for that cluster are case insensitive; that is, the

case of strings is ignored. For example, the string “ab” will match occurrences of “ab”, “Ab”, “aB”, and “AB”. If

ignore case is

not

set on the cluster, then all string comparisons are by default case sensitive (the string “ab” will

match only “ab”).

To override the ignore case flag setting on the cluster for a match function or block of functions, you must logically

AND the observe_case() or ignore_case() functions with the match function or block. For example, if ignore

case is set on the cluster, you would use the following expression to force the header_substr() function to make

case sensitive string comparisons:

(observe_case() and header_substr(\"host\", \"MySystem\"))

Regular Expressions

Some match functions have

prefix

suffix

substr

, or

regex

variants. The

regex

variants interpret an argument as a

regular expression to match against requests. Regular expressions can be very costly to compute, so use the

prefix

suffix

, or

substr

variants of functions (or Boolean combinations of prefix and suffix testing), rather than the

regex

function variants, for best performance. For example, the following regular expression match:

dirname_regex(\"(two|four|six|eight)\")

Can be replaced by the more efficient:

dirname_substr(\"two\") OR

dirname_substr(\"four\") OR

dirname_substr(\"six\") OR

dirname_substr(\"eight\")

Note that Equalizer match rule expressions support POSIX regular expression syntax only.

Supported Headers

All of the header_* match functions take a header argument, which selects the header of interest. If this header is

not present in the request, the match function evaluates to

false

. Otherwise, the text associated with the header is

examined depending on the particular function.

Although HTTP permits a header to span multiple request lines, none of the functions matches text on more than

one line. In addition, Equalizer will only parse the first instance of a header. If, for example, a request has multiple

cookie headers, Equalizer will only match against the first cookie header in the request.

The list of supported headers for the header argument are as follows:

Accept From Referer

Accept-Charset Host TE

Accept-Encoding If-Match Trailer

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