Drools using large RAM for larger rules - spring

Question

We have started using Drools [V 7.55.0.Final]. We have a requirement where we have large number of rules (~100,000) but have few(1-10) facts to process for every API request. A sample of each rule is as follows:
rule "Rule-000000-2627"
when
discountObject: Discount(purchaseSource == "FLIPKART" && customerType == "NEW" && bank == "HDFC" &&
purchaseType == "BNPL" && apparelType == "SHIRT" && price >= 100 && price < 200)
then
discountObject.setDiscount(2);
end
The discount object is as follows:
public class Discount {
private String name;
private String purchaseSource;
private String customerType;
private String bank;
private String purchaseType;
private String apparelType;
private int price;
private int discount;
}
The Drools configuration is as follows:
public class DroolDiscountConfig {
private KieServices kieServices = KieServices.Factory.get();
#Value( "${drool.rule.file}" )
private String droolConfigFile;
private KieFileSystem getKieFileSystem() throws IOException {
KieFileSystem kieFileSystem = kieServices.newKieFileSystem();
Long startTime = Utility.startTime();
String[] droolFiles = this.droolConfigFile.split(",");
for(String droolFile: droolFiles) {
kieFileSystem.write(ResourceFactory.newFileResource(droolFile));
}
Long elapseTime = Utility.elapsedTime(startTime);
System.out.println("Completed loading drool file " + droolConfigFile + " in " + elapseTime);
return kieFileSystem;
}
#Bean
public KieContainer getKieContainer() throws IOException {
System.out.println("Container created...");
getKieRepository();
Long startTimeKieBuilder = Utility.startTime();
KieBuilder kb = kieServices.newKieBuilder(getKieFileSystem());
kb.buildAll();
System.out.println("Kie builder took " + Utility.elapsedTime(startTimeKieBuilder));
Long startTimeKieModule = Utility.startTime();
KieModule kieModule = kb.getKieModule();
System.out.println("Kie Module generation took " + Utility.elapsedTime(startTimeKieModule));
Long startTimeKieContainer = Utility.startTime();
KieContainer kContainer = kieServices.newKieContainer(kieModule.getReleaseId());
System.out.println("KieContainer generation took " + Utility.elapsedTime(startTimeKieContainer));
return kContainer;
}
private void getKieRepository() {
Long startTimeKieRepo = Utility.startTime();
final KieRepository kieRepository = kieServices.getRepository();
kieRepository.addKieModule(new KieModule() {
public ReleaseId getReleaseId() {
return kieRepository.getDefaultReleaseId();
}
});
System.out.println("KieRepo generation took " + Utility.elapsedTime(startTimeKieRepo));
}
}
The Controller is as follows:
#RestController
public class DiscountController {
#Autowired
private KieContainer kieContainer;
#PostMapping("/discount")
public List<Discount> viewDiscount(#RequestBody List<Discount> discounts) {
StatelessKieSession statelessKieSession = kieContainer.newStatelessKieSession();
statelessKieSession.execute(discounts);
return discounts;
}
}
The rule file (single drl file) is of size 40Mb. Whenever, we are starting a service, it occupies around 5-6Gb of RAM. I checked the memory dump using VisualVM but did not find much detail as most of the memory was occupied by bytes[] and Strings[].
I would like to know, are we using Drools in the right way. How can we avoid this huge memory consumption.
Also there are two other issues we are facing:
The first API request takes long time to respond (around 30 seconds).
The service takes long time to start (around 5mins)
If we try to restrict the size of the VM to around 3-4Gb then we get the following error
ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt:
org.springframework.beans.factory.UnsatisfiedDependencyException:
Error creating bean with name 'discountController': Unsatisfied dependency expressed through field 'kieContainer'; nested exception is
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'getKieContainer' defined in class path resource
[load/test/DroolDiscountConfig.class]: Bean instantiation via factory method failed; nested exception is
org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.kie.api.runtime.KieContainer]:
Factory method 'getKieContainer' threw exception; nested exception is java.lang.OutOfMemoryError: Java heap space