[rules-users] How to pre compile rule files for production

[Michael Rhoden]

Yes something like that should work fine. I'm not to up on the 
"synchronized" call you're making but if you can access some app scoped 
memory, what you have will work fine. I might suggest you try and cache 
the rulebases [call execute(String ruleFile, Object [] objects)] well 
before you expect them to perform well, maybe at app startup. It seems, 
for us anyway, that the rulebase building takes hundreds of times longer 
than the rest. 

-Michael

-----Original Message-----
From: rules-users-bounces at lists.jboss.org 
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of 
abhilashkumar at amritatech.com
Sent: Sunday, April 15, 2007 4:23 AM
To: Rules Users List
Subject: Re: [rules-users] How to pre compile rule files for production

Hi Michael,

  Thanks very much  for the instant reply. In my application, I have 
number of .drl files for differnt kinds of domain problems and i pass 
the .drl file name to the RuleExecuter from the EJB. The RuleExecuter 
will fetch and load the rule file into RuleBase and then execute the 
rule.

  So, if i rewrite the code to store the RuleBase in a static HashMap 
(with synchronized put) when it is created for the first time and then 
get it from there for subsequent use,  whether it will be fine? My code 
will now look like the below one. Please give your advice on this.

Thanks and Regards,

 -- Abhilash.

  // This HashMap will act as the cache for RuleBase instances of each 
rule in .drl file
  private static HashMap ruleBaseCache =  null;

  static {
  	ruleBaseCache = new HashMap();
  }


  /**
    * @param ruleFile   - Name of the rule file (.drl file)
    * @param objects    - Fact objects for the rule
    * @return
    * @throws AppException
    */

  private static RuleResultVO execute( String ruleFile, Object [] 
objects
) throws AppException {

         /* This will contain the execution result of the rule. Every 
rule will have reference to
          * this object and will finally store the result in this object
          */
  	RuleResultVO ruleResult = new RuleResultVO();

  	try {


  		//See whether the ruleBase for this rule file is in cache.
Theoretically, this also should be synchrnoized, but will be a 
performance overhead.
  		RuleBase ruleBase = (RuleBase) ruleBaseCache.get( ruleFile 
);

  		if ( ruleBase == null ) {  // First time access. Create the 
ruleBase and put it in cache

  			synchronized( RuleExecuter.ruleBaseCache ) {
                      		//Read the rule source file
  				InputStream in = 
ResourceLoader.getResourceAsStream(ruleFile);
  			        Reader reader = new InputStreamReader(in);
  			        DrlParser parser = new DrlParser();
  			        PackageDescr packageDescr = parser.parse( 
reader );

  			        //pre build the package
  			        PackageBuilder builder = new PackageBuilder();
  			        builder.addPackage( packageDescr );
  			        Package pkg = builder.getPackage();

  			        //add the package to a rulebase
  			        ruleBase = RuleBaseFactory.newRuleBase();
  			        ruleBase.addPackage( pkg );

  			        //Add the RuleBase to the cache so that the 
subsequent calls will use it from there.
  			        ruleBaseCache.put( ruleFile, ruleBase );
  			}
  		}


  	        //create the WorkingMemory
  	        WorkingMemory workingMemory = 
ruleBase.newWorkingMemory();

  	        //Supply the fact objects for the rule
  	        for ( int i = 0; i < objects.length; i++ ) {
  	        	workingMemory.assertObject( objects[i] );
  	        }

  	        workingMemory.assertObject( ruleResult );

  	        // go !
  	        workingMemory.fireAllRules();


  		}catch( Exception e ) {
  			e.printStackTrace();
  			ExceptionUtil.throwAppException( 
"RuleExecuter.executeRule() :
Exception Occured :[" +e.getMessage()+"]");
  		}

          return ruleResult;
  }







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