This adds support for calculating the Bandwidth-delay product when using
HTTP2. When a DATA frame is received, a PING is sent to the remote.
While the PING acknoledgement is outstanding, the amount of bytes of all
received DATA frames is accumulated. Once we receive the PING
acknowledgement, we calculate the BDP based on the number of received
bytes and the round-trip-time of the PING. If we are near the current
maximum window size, the size is doubled.
It's disabled by default until tested more extensively.
- Placed all cases of "unexpected bytes" errors into the
`UnexpectedMessage` variant.
- Placed all cases of "unexpected EOF" errors into the
`IncompleteMessage` variant. Description is now generic about
"connection closed before message completed", instead of mentioning
"request" or "response.
- Added `Error::is_incomplete_message()` accessor to help checking for
unexpected closures.
- Renamed some variants to be clearer when viewing the `Debug` format.
- Collected all "user" errors into an internal `User` enum, to prevent
forgetting to update the `is_user()` method.
Until this commit, servers have required that `Service` and their
`Future` to be `Send`, since the server needs to spawn some internal
tasks to an executor, and by default, that is `tokio::spawn`, which
could be spawning to a threadpool. This was true even if the user were
certain there was no threadpool involved, and was instead using a
different single-threaded runtime, like
`tokio::runtime::current_thread`.
This changes makes all the server pieces generic over an `E`, which is
essentially `Executor<PrivateTypes<Server::Future>>`. There's a new set
of internal traits, `H2Exec` and `NewSvcExec`, which allow for the type
signature to only show the generics that the user is providing. The
traits cannot be implemented explicitly, but there are blanket
implementations for `E: Executor<SpecificType>`. If the user provides
their own executor, it simply needs to have a generic `impl<F>
Executor<F> for MyExec`. That impl can have bounds deciding whether to
require `F: Send`. If the executor does require `Send`, and the
`Service` futures are `!Send`, there will be compiler errors.
To prevent a breaking change, all the types that gained the `E` generic
have a default type set, which is the original `tokio::spawn` executor.
Automatically removes "connection" headers before sending over HTTP2.
These headers are illegal in HTTP2, and would otherwise cause errors.
Closes: #1551
