Add new configuration: minimum count of elements.

[xuxiaocheng0201]

In my particular example, I need to retain at least one element in the pool. Is there any way to achieve this?

[bikeshedder]

What are you trying to do? Are you calling deadpool::managed::Pool::retain and just want one element to exist afterwards?

The simplest way I can think of would be this:

let item = pool.get().await;
pool.retain(|_, _| false);

This would cause one object to be grabbed from the pool. Then retain removes all other elements and afterwards that element is returned back to the pool.

This might actually be related to:

• Shrinking pool size when not in heavy use #299

[xuxiaocheng0201]

Thanks for your quick reply.

Actually the retain isn't what I want. I want at least one element which has the same lifetime with the pool.
A tuple containing a element and the pool is possible. But this is not perfect because the extra element cannot be used.

[xuxiaocheng0201]

This is duplicate with #245. I will subscribe that issus.