quick loading of a drools knowledge base

Question

I'm trying to use Drools as the rule engine for a grammar relations to semantics mapping framework. The rule base is in excess of 5000 rules even now and will get extended. In using Drools currently the reading of the drl file containing the rules and creating the knowledge base takes a lot of time each time the program is run. Is there a way create the knowledge base once and save it in some persistent format that can be quickly loaded with the option to regenerate the knowledge base only when a change is made?

Answer 1

Yes, drools can serialise a knowledgebase out to external storage and then load this serialised knowledgebase back in again.

So, you need a cycle that loads from drl, compiles, serialises out. Then a second cycle that uses the serialised version.

I've used this with some success, reducing a 1 minute 30 loading time down to about 15-20 seconds. Also, it reduces your heap/perm gen requirements as well.

Check the API for the exact methods.

Answer 2

My first thought is to keep the knowledge base around as long as possible. Unless you are creating multiple knowledge bases from different sets of rules, and there are too many possible combinations, hang onto those knowledge bases. In one application I work on, one knowledge base has all the rules so we treat it like a singleton.

However, if that's not possible or your application is not that long-running, I don't know that Drools itself provides any ways of speeding that up. Running a Drools 5.0 project through the debugger, I see that the KnowledgeBase Drools gives me is Serializable. I imagine it would be quicker to deserialize a KnowledgeBase than to re-parse the rules. But be careful designing your application around this! You use interfaces for a reason and the implementation could change without warning.