Difference between DataflowBlockOptions.BoundedCapacity and BufferBlock

Question

Let's assume i have a simple ActionBlock<int>

var actionBlock = new ActionBlock<int>(_ => Console.WriteLine(_));

I can specify a bounded capacity to enable buffering:

var actionBlock = new ActionBlock<int>(
    _ => Console.WriteLine(_),
    new ExecutionDataflowBlockOptions
    { 
        BoundedCapacity = 1000
    });

Is it better to create a BufferBlock<T> and link it to the actionBlock, is it the same, Or is it redundant?

I've wondered this as well. My best guess its intended use is for when you need to buffer at a branch in your flow. — Cory Nelson, Jan 02 '14 at 20:19

score 11 · Accepted Answer · answered Jan 03 '14 at 22:23

If you just added the bounded BufferBlock before your ActionBlock, then that wouldn't work correctly, because the ActionBlock would still be unbounded. So, items would keep accumulating in the ActionBlock's input queue, achieving nothing.

If you added the bounded BufferBlock and also set BoundedCapacity of the ActionBlock to 1, then that would work (plus minus 1).

Doing it this way doesn't give you much (except adding some small overhead), so generally speaking, you should just set BoundedCapacity of the ActionBlock. But there might be some cases where the combination of a bounded BufferBlock and an ActionBlock bounded to 1 might make sense. For example, when you want to set the capacity only after creating the ActionBlock.

(or @i3arnon) I am combing the posts trying to find an answer as to why an execution block with `BoundedCapacity=1` still seems to accept two messages at startup. What did you mean by _that would work (plus minus 1)_? — mdisibio, Nov 12 '21 at 07:43

Difference between DataflowBlockOptions.BoundedCapacity and BufferBlock

1 Answers1