Workflow: 1. Create and deploy policy into policy engine(drool engine) 2. Policy sync synchronize latest policy from engine to container file system. 3. CBS fetch latest policy from file system to slicems memory throgh thread.

Scenario: If a user undeploy an policy, and then deploy a new one. Problem will happen in between when the engine is empty.

If pdp engine is empty, it will cause policies.json in container file system changed. (workflow 2). When it comes to workflow 3, problem happens when cbs find policies.json array length is 0. It will throw an exception. 

Related code: ConfigFetchFromCbs.java in project sonhandler or slicems. The last line in "getAppConfig()" 

Screenshots Explanation: 

We can see that policy sync can always working fine and always update data to policies.json.

However, if engine is empty, then update policies.json to screenshot "policiesJsonFileScreenshot". This will cause exception in screenshot "cbs exception", cause thread hung up.