[ahpearce]

As others have said, there may not be an 'event'. Some metrics need to be monitored manually before setting up an event to trigger. Sure, you might have engineers analyzing the time series data, but you also need to keep your systems up. There are multiple failure modes for various services that may require different action.

For example, perhaps you have some poorly written legacy service that has a memory leak. Let's just say for the sake of this argument, that any sort of boolean indicators (e.g. checking if the process is running) will give you an 'Okay' or green. You are still probably interested in monitoring the memory usage to make sure the service is operating correctly and/or performant. After monitoring for some time, maybe you determine your ops engineers are taking some action whenever the memory gets around 80% or something... then you can setup the trigger event. But without that manual monitoring upfront, you can't just magically set that threshold.