Drools global variable initialization and scaling for performance

Question

Thanks in advance. We are trying to adopt drools as rules engine in our enterprise. After evaluating basic functionality in POC mode, we are exploring further. We have the following challenges and I am trying to validate some of the options we are considering. Any help is greatly appreciated.

Scenario-1: Say you get USA state (TX,CA,CO etc) in a fact's field. Now you want the rule to check if the 'state value on the fact' exists in a predetermined static list of state values(say the list contains three values TX,TN,MN).

Possible solution to Scenario-1: 'static list of state values' can be set as a global variable and the rule can access the global variable while performing the check.

Qustions on Scenario-1: Is the 'possible solution to scenario-1' the standard practice? If so, is it possible to load the value of this global variable from a database during rule engine(KIE Server) startup? If yes, could you let me know the drools feature that enables us to load global variables from a database? Should a client application (a client application that calls kie-server) initialize global variables instead?

Scenario-2: We want to horizantally scale rule execution sever. Say we have one rule engine server(kie-server) exposing rest-api. Can we have multiple instances running behind a loadbalancer to have it scale horizontally? Is there any other way of achieving the scalability?

laune laune · Accepted Answer · 2017-01-09T06:23:40

Q1: It depends. The usual solution for a small, rarely (if ever) changing set that is used just in a single rule is to put it into the rule, using the in operator. If you think you might have to change it or use it frequently, a global would be one way of achieving that but you must make sure that the global is initialized before any facts are inserted.

There is nothing out-of-the-box for accessing a DB.

Q2: A server running a Drools session is just another Java server program, so any load balancing applicable to this class of programs should apply to a Drools app as well. What are you fearing?

Drools global variable initialization and scaling for performance

Thanks in advance. We are trying to adopt drools as rules engine in our enterprise. After evaluating basic functionality in POC mode, we are exploring further. We have the following challenges and I am trying to validate some of the options we are considering. Any help is greatly appreciated.

1 Answers