Log when dropping data outside "windowPeriod"?

[RandomEtc]

Following our discussion on Google Groups:
https://groups.google.com/d/msg/druid-development/ag7EyEIftqQ/QBRNoFxuWMsJ

It might help the learning curve for Druid if the logs indicated when data was dropped. I assume it's a rare occurrence in a properly configured Realtime node, so the overhead would be minimal, but when experimenting with RealtimeStandaloneMain this was a confusing side-road and difficult to understand what was going on :)

[cheddar]

RandomEtc. it actually does log it, but at debug level instead of info. In a production setting, it's actually not uncommon to have a flurry of late events (if a server goes down for some time and then comes back up and pushes everything it has queued up, for example), so logging it on every occurrence actually wouldn't be great.

We should perhaps look at turning debug logging on for the relevant classes for the demos so that it's easier to see there though. If we had done that, do you think it would've helped you out?

Also, the system maintains a count of the number of messages that it dropped, which it emits every minute (with the demo configurations, this is emitted to the logs at debug level).

[RandomEtc]

It would probably have helped, yes. But if debug logging is extremely chatty then perhaps not. It may just be necessary learning curve at the moment, and it will go away when there are examples that can correctly import historical data.