12.7. Cloud Mode

Cloud mode is the default operating mode of JBoss Business Rules Management System.
Running in Cloud mode, the engine applies a many-to-many pattern matching algorithm, which treats the events as an unordered cloud. Events still have timestamps, but there is no way for the rules engine running in Cloud mode to draw relevance from the timestamp because Cloud mode is unaware of the present time.
This mode uses the rules constraints to find the matching tuples, activate, and fire rules.
Cloud mode does not impose any kind of additional requirements on facts; however, because it has no concept of time, it cannot take advantage of temporal features such as sliding windows or automatic life-cycle management. In Cloud mode, it is necessary to explicitly retract events when they are no longer needed.
Certain requirements that are not imposed include the following:
  • No need for clock synchronization since there is no notion of time.
  • No requirement on ordering events since the engine looks at the events as an unordered cloud against which the engine tries to match rules.
Cloud mode can be specified either by setting a system property, using configuration property files, or via the API.
The API call follows: 
KieBaseConfiguration config = KieServices.Factory.get().newKieBaseConfiguration();
   config.setOption( EventProcessingOption.CLOUD );
The equivalent property follows: 
drools.eventProcessingMode = cloud
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