public static boolean isRegistered(String functionId) {
    return getFunctionExecutionService().isRegistered(functionId);
  }
Returns true if the function is registered to FunctionService

@param functionId the ID of the function
@return whether the function is registered to FunctionService

@throws FunctionException if function instance passed is null or Function.getId() returns null
@since GemFire 6.0
geode-core/src/main/java/org/apache/geode/cache/execute/FunctionService.java