Brocade Communications Systems ServerIron ADX 12.4.00 Service Manual download pdf (Page 12)

2 ServerIron ADX OpenScript Guide

53-1002445-01

Overview of OpenScript

Extensibility

Perl was selected for the OpenScript platform because it is open and modular which allows new

functionality to be added easily. In addition to the support provided by Brocade, CPAN

(Comprehensive Perl Archive Network), is one of the largest repositories of free code in the world. If

you need a particular type of functionality, chances are there are several options on the CPAN, and

there are no fees or ongoing costs for using it. While it's possible to download one or more CPAN

Perl modules and install them via a user script on a version updates, the users must do so entirely

at their own risk. We recommend using Perl Extensions that either come pre-loaded with the

ServerIron ADX or approved by Brocade.

Ubiquity

Perl is one of the most heavily used scripting languages for a multitude of applications from text

processing to Apache web server traffic processing. It is easy to use, efficient and complete.

ServerIron ADX-specific functionality such as server load balancing and content transformation

within Perl are exposed to the user via custom extensions that are familiar and easy to use. The

extension interface for ServerIron ADX Perl modules has been designed to mirror the functionality

available on CPAN. The difference is that ServerIron ADX Perl Extensions are optimized for most

common use cases and hide the backend complexity from the script writer. Perl also has an

extensive user and developer community to publish and share scripts covering popular deployment

scenarios.

Why OpenScript uses Perl instead of TCL

Besides Perl, TCL is another scripting platform that is popular in the Industry and applicable for

ServerIron ADX. TCL is a well established scripting platform that finds popular use in the embedded

device environment. Factors favoring TCL are familiarity, stability and extensibility. It offers a C API

to extend scripting functionality via native C code.

The primary concern with embedding TCL is performance. Like the UNIX shell, TCL is a purely

interpretive language. This means that TCL is interpreted each step along the way. Although TCL is

run with a small and efficient interpreter, Perl which is first compiled and then run via an

intermediate byte code representation is inherently faster at execution.

Table 1 describes the advantages and disadvantages to using Perl and TCL.

TABLE 1 comparison between Perl and TCL

Perl Tcl

Advantages Rich language features.

Rich libraries (CPAN)

Fast performance with the compile and

run module

Popular with Server Load Balancing vendors.

Disadvantages Bulkier with a larger dependency

baggage.

Performance lags because Tcl is a pure

interpretive language.

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