Run custom java code as early as possible during app startup

I want to call Core.registerLogSubscriber() to send logged error messages to Sentry. Preferably, I want to call it before the first message is logged that is “Initializing runtime...”. The only option I know is an “After startup” microflow, but I think it starts too late. I also tried a javax.servlet.ServletContextListener implementation annotated with @javax.servlet.annotation.WebListener, but the class didn’t load (I put it in the same Eclipse project where my custom actions are). What about custom OSGI components? How hard is it to add one?  
1 answers

We do something similar and have the setup as the first action in our After Startup microflow. I believe this is the earliest place you perform an action like this. It will be interesting to see if anyone else has a better solution.