libp2p-switch JavaScript implementation

libp2p-switch is a dialer machine, it leverages the multiple libp2p transports, stream muxers, crypto channels and other connection upgrades to dial to peers in the libp2p network. It also supports Protocol Multiplexing through a multicodec and multistream-select handshake.

libp2p-switch is used by libp2p but it can be also used as a standalone module.

Lead Maintainer

Jacob Heun

Table of Contents

• Install
• Usage
  • Create a libp2p switch
• API
  • switch.connection
  • switch.dial(peer, protocol, callback)
  • switch.dialFSM(peer, protocol, callback)
  • switch.handle(protocol, handlerFunc, matchFunc)
  • switch.hangUp(peer, callback)
  • switch.start(callback)
  • switch.stop(callback)
  • switch.stats
  • switch.unhandle(protocol)
  • Internal Transports API
• Design Notes
  • Multitransport
  • Connection upgrades
  • Identify
  • Notes
• Contribute
• License

Install

> npm install libp2p-switch --save

Usage

Create a libp2p Switch

const switch = require('libp2p-switch')

const sw = new switch(peerInfo , peerBook [, options])

If defined, options should be an object with the following keys and respective values:

• blacklistTTL: - number of ms a peer should not be dialable to after it errors. Each successive blacklisting will increase the ttl from the base value. Defaults to 5 minutes

• blackListAttempts: - number of blacklists before a peer is permanently blacklisted. Defaults to 5.

• maxParallelDials: - number of concurrent dials the switch should allow. Defaults to 100

• maxColdCalls: - number of queued cold calls that are allowed. Defaults to 50

• dialTimeout: - number of ms a dial to a peer should be allowed to run. Defaults to 30000 (30 seconds)

• stats: an object with the following keys and respective values:

  • maxOldPeersRetention: maximum old peers retention. For when peers disconnect and keeping the stats around in case they reconnect. Defaults to 100.
  • computeThrottleMaxQueueSize: maximum queue size to perform stats computation throttling. Defaults to 1000.
  • computeThrottleTimeout: Throttle timeout, in miliseconds. Defaults to 2000,
  • movingAverageIntervals: Array containin the intervals, in miliseconds, for which moving averages are calculated. Defaults to:

  [
    60 * 1000, // 1 minute
    5 * 60 * 1000, // 5 minutes
    15 * 60 * 1000 // 15 minutes
  ]

Private Networks

libp2p-switch supports private networking. In order to enabled private networks, the switch.protector must be set and must contain a protect method. You can see an example of this in the private network tests.

API

• peerInfo is a PeerInfo object that has the peer information.
• peerBook is a PeerBook object that stores all the known peers.

switch.connection

switch.connection.addUpgrade()

A connection upgrade must be able to receive and return something that implements the interface-connection specification.

WIP

switch.connection.addStreamMuxer(muxer)

Upgrading a connection to use a stream muxer is still considered an upgrade, but a special case since once this connection is applied, the returned obj will implement the interface-stream-muxer spec.

• muxer

switch.connection.reuse()

Enable the identify protocol.

switch.connection.crypto([tag, encrypt])

Enable a specified crypto protocol. By default no encryption is used, aka plaintext. If called with no arguments it resets to use plaintext.

You can use for example libp2p-secio like this

const secio = require('eth-libp2p-secio')
switch.connection.crypto(secio.tag, secio.encrypt)

switch.connection.enableCircuitRelay(options, callback)

Enable circuit relaying.

• options
  • enabled - activates relay dialing and listening functionality
  • hop - an object with two properties
    • enabled - enables circuit relaying
    • active - is it an active or passive relay (default false)
• callback

switch.dial(peer, protocol, callback)

dial uses the best transport (whatever works first, in the future we can have some criteria), and jump starts the connection until the point where we have to negotiate the protocol. If a muxer is available, then drop the muxer onto that connection. Good to warm up connections or to check for connectivity. If we have already a muxer for that peerInfo, then do nothing.

• peer: can be an instance of [PeerInfo][], [PeerId][] or [multiaddr][]
• protocol
• callback

switch.dialFSM(peer, protocol, callback)

works like dial, but calls back with a Connection State Machine

• peer: can be an instance of [PeerInfo][], [PeerId][] or [multiaddr][]
• protocol: String that defines the protocol (e.g '/ipfs/bitswap/1.1.0') to be used
• callback: Function with signature function (err, connFSM) {} where connFSM is a Connection State Machine

Connection State Machine

Connection state machines emit a number of events that can be used to determine the current state of the connection and to received the underlying connection that can be used to transfer data.

switch.dialer.connect(peer, options, callback)

a low priority dial to the provided peer. Calls to dial and dialFSM will take priority. This should be used when an application only wishes to establish connections to new peers, such as during peer discovery when there is a low peer count. Currently, anything greater than the HIGH_PRIORITY (10) will be placed into the cold call queue, and anything less than or equal to the HIGH_PRIORITY will be added to the normal queue.

• peer: can be an instance of [PeerInfo][], [PeerId][] or [multiaddr][]
• options: Optional
• options.priority: Number of the priority of the dial, defaults to 20.
• options.useFSM: Boolean of whether or not to callback with a Connection State Machine
• callback: Function with signature function (err, connFSM) {} where connFSM is a Connection State Machine

Events

• error: emitted whenever a fatal error occurs with the connection; the error will be emitted.
• error:upgrade_failed: emitted whenever the connection fails to upgrade with a muxer, this is not fatal.
• error:connection_attempt_failed: emitted whenever a dial attempt fails for a given transport. An array of errors is emitted.
• connection: emitted whenever a useable connection has been established; the underlying Connection will be emitted.
• close: emitted when the connection has closed.

switch.handle(protocol, handlerFunc, matchFunc)

Handle a new protocol.

• protocol
• handlerFunc - function called when we receive a dial on protocol. Signature must be function (protocol, conn) {}`
• matchFunc - matchFunc for multistream-select

switch.hangUp(peer, callback)

Hang up the muxed connection we have with the peer.

• peer: can be an instance of [PeerInfo][], [PeerId][] or [multiaddr][]
• callback

switch.on('error', (err) => {})

Emitted when the switch encounters an error.

• err: instance of [Error][]

switch.on('peer-mux-established', (peer) => {})

• peer: is instance of [PeerInfo][] that has info of the peer we have just established a muxed connection with.

switch.on('peer-mux-closed', (peer) => {})

• peer: is instance of [PeerInfo][] that has info of the peer we have just closed a muxed connection with.

switch.on('connection:start', (peer) => {})

This will be triggered anytime a new connection is created.

• peer: is instance of [PeerInfo][] that has info of the peer we have just started a connection with.

switch.on('connection:end', (peer) => {})

This will be triggered anytime an existing connection, regardless of state, is removed from the switch's internal connection tracking.

• peer: is instance of [PeerInfo][] that has info of the peer we have just closed a connection with.

switch.on('start', () => {})

Emitted when the switch has successfully started.

switch.on('stop', () => {})

Emitted when the switch has successfully stopped.

switch.start(callback)

Start listening on all added transports that are available on the current peerInfo.

switch.stop(callback)

Close all the listeners and muxers.

• callback

Stats API

switch.stats.emit('update')

Every time any stat value changes, this object emits an update event.

Global stats

switch.stats.global.snapshot

Should return a stats snapshot, which is an object containing the following keys and respective values:

• dataSent: amount of bytes sent, Big number
• dataReceived: amount of bytes received, Big number

switch.stats.global.movingAverages

Returns an object containing the following keys:

• dataSent
• dataReceived

Each one of them contains an object that has a key for each interval (60000, 300000 and 900000 miliseconds).

Each one of these values is an exponential moving-average instance.

Per-transport stats

switch.stats.transports()

Returns an array containing the tags (string) for each observed transport.

switch.stats.forTransport(transportTag).snapshot

Should return a stats snapshot, which is an object containing the following keys and respective values:

• dataSent: amount of bytes sent, Big number
• dataReceived: amount of bytes received, Big number

switch.stats.forTransport(transportTag).movingAverages

Returns an object containing the following keys:

dataSent dataReceived

Each one of them contains an object that has a key for each interval (60000, 300000 and 900000 miliseconds).

Each one of these values is an exponential moving-average instance.

Per-protocol stats

switch.stats.protocols()

Returns an array containing the tags (string) for each observed protocol.

switch.stats.forProtocol(protocolTag).snapshot

Should return a stats snapshot, which is an object containing the following keys and respective values:

• dataSent: amount of bytes sent, Big number
• dataReceived: amount of bytes received, Big number

switch.stats.forProtocol(protocolTag).movingAverages

Returns an object containing the following keys:

• dataSent
• dataReceived

Each one of them contains an object that has a key for each interval (60000, 300000 and 900000 miliseconds).

Each one of these values is an exponential moving-average instance.

Per-peer stats

switch.stats.peers()

Returns an array containing the peerIDs (B58-encoded string) for each observed peer.

switch.stats.forPeer(peerId:String).snapshot

Should return a stats snapshot, which is an object containing the following keys and respective values:

• dataSent: amount of bytes sent, Big number
• dataReceived: amount of bytes received, Big number

switch.stats.forPeer(peerId:String).movingAverages

Returns an object containing the following keys:

• dataSent
• dataReceived

Each one of them contains an object that has a key for each interval (60000, 300000 and 900000 miliseconds).

Each one of these values is an exponential moving-average instance.

Stats update interval

Stats are not updated in real-time. Instead, measurements are buffered and stats are updated at an interval. The maximum interval can be defined through the Switch constructor option stats.computeThrottleTimeout, defined in miliseconds.

switch.unhandle(protocol)

Unhandle a protocol.

• protocol

Internal Transports API

switch.transport.add(key, transport, options)

libp2p-switch expects transports that implement interface-transport. For example libp2p-tcp.

• key - the transport identifier.
• transport -
• options -

switch.transport.dial(key, multiaddrs, callback)

Dial to a peer on a specific transport.

• key
• multiaddrs
• callback

switch.transport.listen(key, options, handler, callback)

Set a transport to start listening mode.

• key
• options
• handler
• callback

switch.transport.close(key, callback)

Close the listeners of a given transport.

• key
• callback

Design Notes

Multitransport

libp2p is designed to support multiple transports at the same time. While peers are identified by their ID (which are generated from their public keys), the addresses of each pair may vary, depending the device where they are being run or the network in which they are accessible through.

In order for a transport to be supported, it has to follow the interface-transport spec.

Connection upgrades

Each connection in libp2p follows the interface-connection spec. This design decision enables libp2p to have upgradable transports.

We think of upgrade as a very important notion when we are talking about connections, we can see mechanisms like: stream multiplexing, congestion control, encrypted channels, multipath, simulcast, etc, as upgrades to a connection. A connection can be a simple and with no guarantees, drop a packet on the network with a destination thing, a transport in the other hand can be a connection and or a set of different upgrades that are mounted on top of each other, giving extra functionality to that connection and therefore upgrading it.

Types of upgrades to a connection:

• encrypted channel (with TLS for e.g)
• congestion flow (some transports don't have it by default)
• multipath (open several connections and abstract it as a single connection)
• simulcast (still really thinking this one through, it might be interesting to send a packet through different connections under some hard network circumstances)
• stream-muxer - this a special case, because once we upgrade a connection to a stream-muxer, we can open more streams (multiplex them) on a single stream, also enabling us to reuse the underlying dialed transport

We also want to enable flexibility when it comes to upgrading a connection, for example, we might that all dialed transports pass through the encrypted channel upgrade, but not the congestion flow, specially when a transport might have already some underlying properties (UDP vs TCP vs WebRTC vs every other transport protocol)

Identify

Identify is a protocol that switchs mounts on top of itself, to identify the connections between any two peers. E.g:

• a) peer A dials a conn to peer B
• b) that conn gets upgraded to a stream multiplexer that both peers agree
• c) peer B executes de identify protocol
• d) peer B now can open streams to peer A, knowing which is the identity of peer A

In addition to this, we also share the "observed addresses" by the other peer, which is extremely useful information for different kinds of network topologies.

Notes

To avoid the confusion between connection, stream, transport, and other names that represent an abstraction of data flow between two points, we use terms as:

• connection - something that implements the transversal expectations of a stream between two peers, including the benefits of using a stream plus having a way to do half duplex, full duplex
• transport - something that as a dial/listen interface and return objs that implement a connection interface

This module uses pull-streams

We expose a streaming interface based on pull-streams, rather then on the Node.js core streams implementation (aka Node.js streams). pull-streams offers us a better mechanism for error handling and flow control guarantees. If you would like to know more about why we did this, see the discussion at this issue.

You can learn more about pull-streams at:

• The history of Node.js streams, nodebp April 2014
• The history of streams, 2016
• pull-streams, the simple streaming primitive
• pull-streams documentation

Converting pull-streams to Node.js Streams

If you are a Node.js streams user, you can convert a pull-stream to a Node.js stream using the module pull-stream-to-stream, giving you an instance of a Node.js stream that is linked to the pull-stream. For example:

const pullToStream = require('pull-stream-to-stream')

const nodeStreamInstance = pullToStream(pullStreamInstance)
// nodeStreamInstance is an instance of a Node.js Stream

To learn more about this utility, visit https://pull-stream.github.io/#pull-stream-to-stream.

Contribute

This module is actively under development. Please check out the issues and submit PRs!

License

MIT © Protocol Labs