Thread Safety

Why RuleBook and Rule are transient, and what that means for concurrent runs.

Thread Safety

RuleBook and Rule are transient (non-singleton) objects, and given()/givenAll() write facts directly onto the instance's own state. That means a single RuleBook instance is not safe to run() concurrently from multiple threads, or with different facts across separate calls - the facts and the rule status audit trail accumulate on that instance across every run() call.

Always request a fresh transient instance (e.g. getInstance( "MyRuleBook" )) per invocation, whether that invocation happens on a separate thread or simply at a separate point in time with different facts. A RuleBook instance is only safe to run() again if it's given the exact same facts it already holds.

Builder@rulebox itself is a @singleton @threadsafe class - it's safe to share a single instance of the builder across threads, since it only ever hands back fresh RuleBook/Rule transients rather than holding request-specific state itself.