Avoid MDC outside try statement

[dgroup]

Summary

Key	Value
Rule	PotentiallyThreadLocalPollutionByMdc
Ruleset	io/github/dgroup/arch4u/pmd/arch4u-ruleset.xml
Category	Error Prone
Framework	org.slf4j:slf4j-api, org.apache.logging.log4j:log4j-api
Since	0.1.0
Incidents in past at my experience	4

Why?

MDC API should always be used within the try/finally statement:

private static final Logger LOG = ...

public ... process(Order order) throws ... {
   try {
         MDC.put("order", order.getId());
         MDC.put("customer", order.getCustomerId());
         LOG.debug("Order {} initiated for {}", order.geId(), order.getCustomerId());
   
         // .. business logic

   } finally {
         MDC.remove("order");
         MDC.remove("customer");
   }      
   return ...
}

If an exception happens and the developer isn't using the finally statement the thread-local value might not be cleaned and we'll have thread pollution.