[litep2p](https://github.com/altonen/litep2p) is a libp2p-compatible P2P
networking library. It supports all of the features of `rust-libp2p`
that are currently being utilized by Polkadot SDK.
Compared to `rust-libp2p`, `litep2p` has a quite different architecture
which is why the new `litep2p` network backend is only able to use a
little of the existing code in `sc-network`. The design has been mainly
influenced by how we'd wish to structure our networking-related code in
Polkadot SDK: independent higher-levels protocols directly communicating
with the network over links that support bidirectional backpressure. A
good example would be `NotificationHandle`/`RequestResponseHandle`
abstractions which allow, e.g., `SyncingEngine` to directly communicate
with peers to announce/request blocks.
I've tried running `polkadot --network-backend litep2p` with a few
different peer configurations and there is a noticeable reduction in
networking CPU usage. For high load (`--out-peers 200`), networking CPU
usage goes down from ~110% to ~30% (80 pp) and for normal load
(`--out-peers 40`), the usage goes down from ~55% to ~18% (37 pp).
These should not be taken as final numbers because:
a) there are still some low-hanging optimization fruits, such as
enabling [receive window
auto-tuning](https://github.com/libp2p/rust-yamux/pull/176), integrating
`Peerset` more closely with `litep2p` or improving memory usage of the
WebSocket transport
b) fixing bugs/instabilities that incorrectly cause `litep2p` to do less
work will increase the networking CPU usage
c) verification in a more diverse set of tests/conditions is needed
Nevertheless, these numbers should give an early estimate for CPU usage
of the new networking backend.
This PR consists of three separate changes:
* introduce a generic `PeerId` (wrapper around `Multihash`) so that we
don't have use `NetworkService::PeerId` in every part of the code that
uses a `PeerId`
* introduce `NetworkBackend` trait, implement it for the libp2p network
stack and make Polkadot SDK generic over `NetworkBackend`
* implement `NetworkBackend` for litep2p
The new library should be considered experimental which is why
`rust-libp2p` will remain as the default option for the time being. This
PR currently depends on the master branch of `litep2p` but I'll cut a
new release for the library once all review comments have been
addresses.
---------
Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: Dmitry Markin <dmitry@markin.tech>
Co-authored-by: Alexandru Vasile <60601340+lexnv@users.noreply.github.com>
Co-authored-by: Alexandru Vasile <alexandru.vasile@parity.io>
Previously, it was only possible to retry the same request on a
different protocol name that had the exact same binary payloads.
Introduce a way of trying a different request on a different protocol if
the first one fails with Unsupported protocol.
This helps with adding new req-response versions in polkadot while
preserving compatibility with unupgraded nodes.
The way req-response protocols were bumped previously was that they were
bundled with some other notifications protocol upgrade, like for async
backing (but that is more complicated, especially if the feature does
not require any changes to a notifications protocol). Will be needed for
implementing https://github.com/polkadot-fellows/RFCs/pull/47
TODO:
- [x] add tests
- [x] add guidance docs in polkadot about req-response protocol
versioning
Submit the outstanding PRs from the old repos(these were already
reviewed and approved before the repo rorg, but not yet submitted):
Main PR: https://github.com/paritytech/substrate/pull/14014
Companion PRs: https://github.com/paritytech/polkadot/pull/7134,
https://github.com/paritytech/cumulus/pull/2489
The changes in the PR:
1. ChainSync currently calls into the block request handler directly.
Instead, move the block request handler behind a trait. This allows new
protocols to be plugged into ChainSync.
2. BuildNetworkParams is changed so that custom relay protocol
implementations can be (optionally) passed in during network creation
time. If custom protocol is not specified, it defaults to the existing
block handler
3. BlockServer and BlockDownloader traits are introduced for the
protocol implementation. The existing block handler has been changed to
implement these traits
4. Other changes:
[X] Make TxHash serializable. This is needed for exchanging the
serialized hash in the relay protocol messages
[X] Clean up types no longer used(OpaqueBlockRequest,
OpaqueBlockResponse)
---------
Co-authored-by: Dmitry Markin <dmitry@markin.tech>
Co-authored-by: command-bot <>
Aaro Altonen