Specifications

Equalizer Installation and Administration Guide 123
8 Working with Match Rules
Why Match Rules?
The ability to make load balancing decisions based on the content of a client request is what
separates Layer 7 processing from the processing options available at Layer 4. For Layer 7 clusters,
Match Rules provide fine-grained control over load balancing decisions based on the content of the
client request. If you need to be able to route requests to the servers in a cluster based on the content
of the request, Match Rules are the answer.
Match Rules Overview
Layer 7 clusters can use logical constructs called “match rules” to control the processing of the
incoming data stream from clients. Match rules extend the Layer 7 load balancing capabilities of
HTTP and HTTPS clusters by allowing you to define a set of logical conditions which, when met by
the contents of the request, trigger the load balancing behavior specified in the match rule.
Typically, a match rule selects the subset of servers that the load balancing algortihms will use for a
particular request. By default, a request is load balanced over all the available non-spare servers in a
cluster. Match rules allow you to select the group of servers that will be used to load balance the
request.
For each virtual cluster, you can specify any number of match rules. For each match rule, you
specify the subset of servers that can handle requests that meet the rule criteria.
A match rule provides for custom processing of requests within connections. Equalizer provides
common and protocol-specific match functions that enable dynamic matching based on the request’s
contents. Protocol-specific match functions typically test for the presence of particular attributes in
the current request.
For example, a Layer 7 HTTP virtual cluster can specify matching on specific pathname attributes
to direct requests to subsets of servers so that all requests for images are sent to the image servers.
The difference between load balancing with and without match rules in such a situation is illustrated
in the following figure.
Note – Match rules are supported on Equalizer Models E350 and higher models; they are not
supported on E250 models.