Andrew Johnson > HeliosX-JSService-0.01_4703 > HeliosX::JSService

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Module Version: 0.01_4703   Source  

NAME ^

HeliosX::JSService - Helios service base class to allow Helios services written in JavaScript

SYNOPSIS ^

In a Perl .pm file:

  # create a Perl stub for your JavaScript service
  package HeliosX::JSTestService;
  use parent qw(HeliosX::JSService);
  sub JSSource { '/path/to/script.js' };
  1;

In a JavaScript .js file:

  // this is a rough equivalent to Helios::TestService, but in JS
  // all we do is log the job arguments and mark the job as completed
 
  /* Helios variables and objects provided to JavaScript:
        HeliosService object, the current instance of the Helios service
        HeliosConfig  hash, the service's current configuration
        HeliosJob     object, the current Helios job
        HeliosJobArg  hash, the current job's arguments           
   */
   
  // log each of the job's arguments in the logging system
  for (var key in HeliosJobArgs) {
      HeliosService.logMsg(HeliosJob, "Argname: " + key + " Value: " + HeliosJobArgs[key]);
  }
  
  // mark the job as completed
  HeliosService.completedJob(Job);

On the command line, use the typical helios.pl service daemon start cmd:

  helios.pl HeliosApp::MyService

DESCRIPTION ^

HeliosX::JSService allows a developer to write Helios services in JavaScript. By using the Mozilla Spidermonkey JavaScript engine and the JSPL Perl/Spidermonkey glue library, HeliosX::JSService can allow the JavaScript developer access to a huge portion of the vast Perl CPAN library from the JavaScript language with which they are familiar. By allowing this access from the Helios environment, JavaScript developers now have access to this vast array of libraries inside a distributed, asynchronous processing environment.

#[] need more info here, it's still a development version

CONFIGURATION PARAMETERS ^

js_src_path

The path to your JavaScript source files. If specified, your Helios service class will attempt to locate your .js files in that location. It is highly recommended you set this parameter in the [global] section of your helios.ini file so you can place all of your .js files in the same location. Otherwise, you will need to set js_src_path for each service you create in the Panoptes Ctrl Panel, or specify a full path in each of your service classes' JSSource() method.

METHODS YOU ARE LOOKING FOR ^

One or more of the following methods need to appear in the Perl stub for your Helios service. The required JSSource() method tells Helios which JavaScript source file to load and run, while the optional configureJSContext() can be used to configure other Perl/CPAN libraries for use by your JavaScript code.

JSSource() REQUIRED

This is the only method you normally need to worry about in your Perl module stub. It tells the Helios service instance the location of the JavaScript source file to load and run.

The Perl stub module for your Helios service can be as short as the following 4 statements:

  package HeliosApp::MyService;
  use parent qw(HeliosX::JSService);
  sub JSSource { '/path/to/script.js' };
  1;

(Don't worry about use strict, use warnings, etc. They will be taken care of for you.)

So if you wanted to write a service called HeliosApp::IndexerService whose code you would put in the /usr/local/lib/js/IndexerService.js file, your Perl stub would look like:

  package HeliosApp::IndexerService;
  use parent qw(HeliosX::JSService);
  sub JSSource { '/usr/local/lib/js/IndexerService.js' };
  1;

If you set the "js_src_path" configuration parameter to "/usr/local/lib/js" in the [global] section of your helios.ini, then your Perl stub would be reduced:

  package HeliosApp::IndexerService;
  use parent qw(HeliosX::JSService);
  sub JSSource { 'IndexerService.js' };
  1;

Helios would automatically look in /usr/local/lib/js for any .js file, so the full path is no longer necessary in JSSource().

configureJSContext(%params)

The configureJSContext() method allows the Helios JavaScript developer access to the JavaScript context created by Helios and JSPL (the glue module between the Perl interpreter and the Mozilla Spidermonkey JavaScript engine). While HeliosX::JSService provides the JavaScript context with access to the necessary Helios objects and variables, the developer needing access to other CPAN modules such as DBI will need to override this method and add Perl code to bind the needed classes into the JSPL context.

#[] need more docs here: what's given and what needs to happen to get it working

See JSPL::Controller for more information on binding Perl classes into your JSPL context.

METHODS YOU ARE NOT LOOKING FOR ^

The following methods work behind the scenes to setup the Helios service instance and initialize the Spidermonkey JS context. Unless you are trying to muck about extending HeliosX::JSService itself, you shouldn't need to pay attention to these. JavaScript developer, these are not the methods you are looking for...

run($job)

This is the typical run() method required by all Helios service classes. It actually doesn't do anything special from a Perl or Helios perspective: it sets up parameters, calls some methods, catches some errors.

getJS()

This method determines where the JavaScript source file is located, loads it into memory, and returns it to the calling routine (most likely the run() method).

The getJS() method will look for the .js file in the location defined by the "js_src_path" config parameter, if it is defined.

createJSContext(%params)

Given a set of Helios-relevant variables, createJSContext() actually creates the JSPL JavaScript context, makes the Helios variables available by binding them to JavaScript variables in the JSPL context, and then calls the configureJSContext() method for any further configuration, returning the resulting context to the calling routine.

The %params variable includes the typical Helios information:

  CONFIG  the service class configuration (hashref)
  JOB     the current job to be processed (Helios::Job object)
  ARGS    the current job's arguments (hashref)

This method is phase 1 of a two phase JSPL context creation process. Splitting context creation into two methods allows the service developer access to the JSPL context without dumping the whole thing in their lap.

SEE ALSO ^

Helios, JSPL, JSPL::Controller

AUTHOR ^

Andrew Johnson, <lajandy at cpan dot org>

COPYRIGHT AND LICENSE ^

Copyright (C) 2011 by Andrew Johnson

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.10.1 or, at your option, any later version of Perl 5 you may have available.

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