You always put a comma in a direct adress if you want your sentence to be grammatically correct.
Using Commas for Direct Address (i.e., the Vocative Case)
When addressing a person or thing directly, the name used must be offset with a comma (or commas if it's mid-sentence). For example:
Jackie, are you leaving so soon?
(Jackie is being addressed directly. Her name is offset with a comma.)
I know your sister, Michael.
(Michael is being addressed directly. His name is offset with a comma.)
When addressing someone directly, writers should separate the name being used (e.g., John, Mary, my darling, you little rascal, my son) from rest of the sentence using a comma or commas.
The person or thing being addressed is said to be in the vocative case.
In each example below, the person or thing in the vocative case is shaded:
Alan, put your hand up if you do not understand.
(Alan is being addressed. The word Alan is said to be in the vocative case.
It must be separated from the rest of the sentence with a comma.
Where do you think you are going, you little devil?
(Somebody is being addressed as you little devil.
Those words are in the vocative case, and a comma is required.
Absolutely, John, get your skates on.
WHAT IS THE VOCATIVE CASE?
When somebody is being addressed directly, his/her name must be separated from the rest of the sentence with a comma (or commas).