114 lines
3.2 KiB
Markdown
114 lines
3.2 KiB
Markdown
# ADR 012: PeerTransport
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## Context
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One of the more apparent problems with the current architecture in the p2p
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package is that there is no clear separation of concerns between different
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components. Most notably the `Switch` is currently doing physical connection
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handling. An artifact is the dependency of the Switch on
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`[config.P2PConfig`](https://github.com/tendermint/tendermint/blob/05a76fb517f50da27b4bfcdc7b4cf185fc61eff6/config/config.go#L272-L339).
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Addresses:
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* [#2046](https://github.com/tendermint/tendermint/issues/2046)
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* [#2047](https://github.com/tendermint/tendermint/issues/2047)
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First iteraton in [#2067](https://github.com/tendermint/tendermint/issues/2067)
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## Decision
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Transport concerns will be handled by a new component (`PeerTransport`) which
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will provide Peers at its boundary to the caller. In turn `Switch` will use
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this new component accept new `Peer`s and dial them based on `NetAddress`.
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### PeerTransport
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Responsible for emitting and connecting to Peers. The implementation of `Peer`
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is left to the transport, which implies that the chosen transport dictates the
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characteristics of the implementation handed back to the `Switch`. Each
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transport implementation is responsible to filter establishing peers specific
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to its domain, for the default multiplexed implementation the following will
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apply:
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* connections from our own node
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* handshake fails
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* upgrade to secret connection fails
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* prevent duplicate ip
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* prevent duplicate id
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* nodeinfo incompatibility
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``` go
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// PeerTransport proxies incoming and outgoing peer connections.
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type PeerTransport interface {
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// Accept returns a newly connected Peer.
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Accept() (Peer, error)
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// Dial connects to a Peer.
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Dial(NetAddress) (Peer, error)
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}
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// EXAMPLE OF DEFAULT IMPLEMENTATION
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// multiplexTransport accepts tcp connections and upgrades to multiplexted
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// peers.
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type multiplexTransport struct {
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listener net.Listener
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acceptc chan accept
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closec <-chan struct{}
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listenc <-chan struct{}
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dialTimeout time.Duration
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handshakeTimeout time.Duration
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nodeAddr NetAddress
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nodeInfo NodeInfo
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nodeKey NodeKey
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// TODO(xla): Remove when MConnection is refactored into mPeer.
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mConfig conn.MConnConfig
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}
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var _ PeerTransport = (*multiplexTransport)(nil)
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// NewMTransport returns network connected multiplexed peers.
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func NewMTransport(
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nodeAddr NetAddress,
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nodeInfo NodeInfo,
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nodeKey NodeKey,
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) *multiplexTransport
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```
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### Switch
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From now the Switch will depend on a fully setup `PeerTransport` to
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retrieve/reach out to its peers. As the more low-level concerns are pushed to
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the transport, we can omit passing the `config.P2PConfig` to the Switch.
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``` go
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func NewSwitch(transport PeerTransport, opts ...SwitchOption) *Switch
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```
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## Status
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In Review.
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## Consequences
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### Positive
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* free Switch from transport concerns - simpler implementation
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* pluggable transport implementation - simpler test setup
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* remove Switch dependency on P2PConfig - easier to test
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### Negative
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* more setup for tests which depend on Switches
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### Neutral
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* multiplexed will be the default implementation
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[0] These guards could be potentially extended to be pluggable much like
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middlewares to express different concerns required by differentally configured
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environments.
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