Update the call_all comment in Inbound
@@ -247,7 +247,11 @@ impl Service<zn::Request> for Inbound {
zn::Request::BlocksByHash(hashes) => {
// Correctness:
//
- // We can't use `call_all` here, because it leaks buffer slots:
+ // We can't use `call_all` here, because it can hold one buffer slot per concurrent
+ // future, until the `CallAll` struct is dropped. We can't hold those slots in this
+ // future because:
+ // * we're not sure when the returned future will complete, and
+ // * we don't limit how many returned futures can be concurrently running
// https://github.com/tower-rs/tower/blob/master/tower/src/util/call_all/common.rs#L112
use futures::stream::TryStreamExt;
hashes
