You'll find more info [here](https://discuss.elastic.co/t/index-name-and-uuid/85709/9?u=hariso
). In short, indices have their own IDs, which are used for the data structure, but you shouldn't be concerned about that. You still use their names in the API, which is the only way you should use ES.
The log lines containing JvmGcMonitorService are normal, and they log activity related to GC (garbage collection).