Currently you require no visa to enter Qatar, and you'll be given a no-fuss visa on arrival if you choose to enter UAE. For Sri Lanka you don't require a visa if you remain airside i.e. don't enter the country.

However getting a 48-hour transit E-visa for Sri Lanka might be reassuring, just in case the connection goes wrong and you need to get to a hotel: it's free and avoids the faff that can be entailed getting the same (free) transit visa at the airport. Online Visa Application