During the refactoring of Minion to use Confd, I found a very interesting change that allows you to add content to the custom.properties file without touching that file directly. That requires having a line there to allow importing the content of another file (called custom.system.properties):
I believe adding that for Sentinel would bring a lot of benefits for the people using it, for the same reasons it was added to Minion.
Here is an example use case:
On my Kubernetes Playground, I use an initContainer to dynamically generate the configuration for Sentinel via overlay (for the Flows/Telemetry use case and for the ALEC use case). Because I must configure the Instance ID, and other elements, for example, storeByGroup or storeByForeignSource or Jaeger, I'm forced to use the sentinel image just to be able to grab the current content of custom.properties, customize it and populate the overlay directory.
If I have the requested feature in place, I can make this initContainer based on bash (or busybox), which are images order of magnitudes smaller, and make the solution cleaner and faster.
I'm in the process of simplifying the initContainer for Minion thanks to this feature, but it would be wonderful if I could simplify the Sentinels as well.
In the case of M2019, and because the idea is to avoid changing the configuration in Meridian when possible, having this in place, allows us to eventually change system.properties in the future without any worry about having a .rpmnew after an upgrade.