ssb-conn

SSB CONN

SSB plugin for establishing and managing peer connections.

Also known as "The Gossip Refactor", the CONN (Connections Over Numerous Networks) plugin replaces the old gossip plugin, covering all its use cases. CONN has these responsibilities:

• Persistence of pub (and other servers) addresses (in the file ~/.ssb/conn.json)
• Monitoring of all current connections and their state (connecting, disconnecting, etc)
• Monitoring of discovered peers and suggested connections (e.g. on LAN or Bluetooth)
• Selection and scheduling of connections and disconnections
• API compatibility with the old gossip plugin

Installation

Prerequisites:

• Requires Node.js 6.5 or higher
• Requires secret-stack@^6.2.0

npm install --save ssb-conn

Add this plugin to ssb-server like this:

 var createSsbServer = require('ssb-server')
     .use(require('ssb-onion'))
     .use(require('ssb-unix-socket'))
     .use(require('ssb-no-auth'))
     .use(require('ssb-plugins'))
     .use(require('ssb-master'))
+    .use(require('ssb-conn'))
     .use(require('ssb-replicate'))
     .use(require('ssb-friends'))
     // ...

Now you should be able to access the muxrpc APIs under ssb.conn and ssb.gossip, see next section.

API

Under ssb.conn.* you can call any of these APIs in your local peer.

API	Type	Description
remember(addr, data?)	sync	Stores (in cold storage) connection information about a new peer, known by its multiserver address addr and additional optional data (as an object).
forget(addr)	sync	Removes (from cold storage) connection information about a peer known by its multiserver address addr.
dbPeers()	sync	Returns an Iterable of ConnDB entries known at the moment. Does not reactively update once the database is written to.
connect(addr, data?)	async	Connects to a peer known by its multiserver address addr, and stores additional optional data (as an object) during its connection lifespan.
disconnect(addr)	async	Disconnects a peer known by its multiserver address addr.
peers()	source	A pull-stream that emits an array of all ConnHub entries whenever any connection updates (i.e. changes it state: connecting, disconnecting, connected, etc).
stage(addr, data?)	sync	Registers a suggested connection to a new peer, known by its multiserver address addr and additional optional data (as an object).
unstage(addr)	sync	Unregisters a suggested connection the peer known by its multiserver address addr.
stagedPeers()	source	A pull-stream that emits an array of all ConnStaging entries whenever any staging status updates (upon stage() or unstage()).
start()	sync	Triggers the start of the connection scheduler in CONN.
stop()	sync	Stops the CONN scheduler if it is currently active.
ping()	duplex	A duplex pull-stream for periodically pinging with peers, fully compatible with ssb.gossip.ping.
db()	sync	Returns the instance of ConnDB currently in use.
hub()	sync	Returns the instance of ConnHub currently in use.
staging()	sync	Returns the instance of ConnStaging currently in use.
query()	sync	Returns the instance of ConnQuery currently in use.

An "entry" is a (tuple) array of form:

[addr, data]

where:

• addr is a multiserver address (a string that follows some rules)
• data is an object with additional information about the peer (fields marked 🔷 are important and often used, fields marked 🔹 come from CONN, fields marked 🔸 are ad-hoc and added by various other modules, and fields suffixed with ? are not always present):

🔷 key: string: the peer's public key / feedId

🔷 state?: 'connecting' | 'connected' | 'disconnecting': (only from peers()) the peer's current connection status

🔷 type?: string: what type of peer this is; it can be any string, but often is either 'lan', 'bt', 'pub', 'room', 'room-endpoint', 'dht'

🔹 inferredType?: 'bt' | 'lan' | 'dht' | 'internet' | 'tunnel': (only from peers()) when there is no type field, e.g. when a new and unknown peer initiates a client connection with us (as a server), then ConnHub makes a guess what type it is

🔹 birth?: number: Unix timestamp for when this peer was added to ConnDB

🔹 stateChange?: number: Unix timestamp for the last time the field state was changed; this is stored in ConnDB

🔹 hubBirth?: number: Unix timestamp for when this peer was added to ConnHub

🔹 hubUpdated?: number: Unix timestamp for when this data object was last updated in ConnHub

🔹 stagingBirth?: number: Unix timestamp for when this peer was added to ConnStaging

🔹 stagingUpdated?: number: Unix timestamp for when this data object was last updated in ConnStaging

🔹 autoconnect?: boolean: indicates whether this peer should be considered for connection in the scheduler

🔹 failure?: number: typically in ConnDB, this is the number of connection errors since the last successful connection

🔹 duration?: object: typically in ConnDB, this is a statistics object to measure the duration of connection with this peer

🔹 ping?: object: typically in ConnDB, this is statistics object of various ping health measurements

🔹 pool?: 'db' | 'hub' | 'staging': this only appears in ConnQuery APIs, and indicates from which pool (ConnDB or ConnHub or ConnStaging) was this peer picked

🔸 name?: string: a nickname for this peer, when there isn't an ssb-about name

🔸 room?: string: (only if type = 'room-endpoint') the public key of the room server where this peer is in

🔸 onlineCount?: number: (only if type = 'room') the number of room endpoints currently connected to this room

Gossip compatibility

The following gossip plugin APIs are available once you install CONN, but these will emit deprecation warnings and might behave slightly different than the old gossip plugin:

API	Type
ssb.gossip.peers()	sync
ssb.gossip.get(p)	sync
ssb.gossip.connect(p)	async
ssb.gossip.disconnect(p)	async
ssb.gossip.changes()	source
ssb.gossip.add(p, source)	sync
ssb.gossip.remove(p)	sync
ssb.gossip.ping()	duplex
ssb.gossip.reconnect()	sync
ssb.gossip.enable()	sync
ssb.gossip.disable()	sync

If you want to use the new CONN infrastructure but preserve the same gossip behavior as before, use ssb-legacy-conn which tries to mirror the gossip plugin, even its log messages.

Learn more

How CONN works (click here)

Under the hood, CONN is based on three "pools" of peers:

• ConnDB: a persistent database of addresses to connect to
• ConnHub: a façade API for currently active connections
• ConnStaging: a pool of potential new connections

ConnDB contains metadata on stable servers and peers that have been successfully connectable. ConnHub is the central API that allows us to issue new connections and disconnections, as well as to track the currently active connections. ConnStaging is an in-memory ephemeral storage of new possible connections that the user might want to approve or disapprove.

Then, ConnQuery has access to those three pools, and provides utilities to query, filter, and sort connections across all those pools.

ConnScheduler is an opinionated (⚠️) plugin that utilizes ConnQuery to select peers to connect to, then schedules connections to happen via ConnHub, as well as schedules disconnections if necessary. Being opinionated, CONN provides an easy way of replacing the default scheduler with your own scheduler, see instructions below.

There is also a Gossip Compatibility plugin, implementing all the legacy APIs, so that other SSB plugins that call these APIs will continue to function as normal.

When you install the ssb-plugin, it will actually setup three plugins:

[conn, connScheduler, gossip]

Opinions built into the default scheduler (click here)

The default scheduler is roughly the same as the legacy ssb-gossip plugin, with some opinions removed and others added. The scheduler has two parts: discovery setup on startup, and periodic connections/disconnections.

Discovery setup:

• Read the SSB log and look for "pub" messages, and remember them
• Listen to a stream of Bluetooth nearby devices, and stage them

Periodic connections/disconnections:

• With (5sec) exponential backoff, try to connect to at most 5 room servers
• With (10sec) exponential backoff, try to connect to at most 2 non-room peers that we have connected successfully before
• With (30sec) exponential backoff, try to connect to at most 2 non-room peers that we have never with connected before
• With (1min) exponential backoff, try to connect to at most 3 non-room peers that have we always failed to connect with
• With (4min) exponential backoff, try to connect to at most 1 non-room peer that seem to run a legacy version of the gossip plugin

In none of the cases above shall we connect to a peer that we block. In addition to the above, the following actions happen automatically every (approximately) 1 second:

• Connect to (at most 3) staged peers we follow
• Disconnect from connected peers that have just been blocked by us
• Disconnect from peers that have been connected with us for more than 30min
• Disconnect from peers that have been pending in "connecting" status for too long
  • "Too long" means 30sec for LAN peers
  • "Too long" means 1min for Bluetooth peers
  • "Too long" means 5min for DHT invite peers
  • For other types of peers, "too long" means 10sec
• Stage non-blocked peers that are in ConnDB, marked as autoconnect=false
• Unstage peers that have just been blocked by us
• Unstage LAN peers that haven't been updated in ConnStaging in 10 seconds
• Unstage Bluetooth peers that haven't been updated in ConnStaging in 30 seconds

Other events:

• Upon wakeup (from computer 'sleep'), fully reset the ConnHub
• Upon network (interface) changes, fully reset the ConnHub
• Upon a disconnection, try to connect to some peer (section above)

How to build your own ConnScheduler (click here)

To experiment with your own opinions for establishing connections, you can make your own ConnScheduler, which is just a typical SSB plugin. You can write in the traditional style (like other SSB plugins), or with OOP decorators. The example below uses OOP decorators.

Here is the basic shape of the scheduler:

import {plugin, muxrpc} from 'secret-stack-decorators';

@plugin('1.0.0')
module.exports = class ConnScheduler {
  constructor(ssb, config) {
    // basic setup here
    this.ssb = ssb;
  }

  @muxrpc('sync')
  public start = () => {
    // this is called when the scheduler should begin scheduling connections

    // You have access to CONN core here:
    const query = this.ssb.conn.query();
    this.ssb.conn.stage(addr);
    this.ssb.conn.disconnect(addr);
    // ...
  }

  @muxrpc('sync')
  public stop = () => {
    // this is called when the scheduler should cancel its jobs
  }
}

Note that the name of the plugin must be exactly ConnScheduler (or connScheduler) and it must have the methods start() and stop(), because the CONN core will try to use your scheduler under those names. The rest of the contents of the ConnScheduler class are up to you, you can use private methods, etc.

When you're done building your scheduler, you can export it together with CONN core and the gossip compatibility plugin like this:

var CONN = require('ssb-conn/core')
var Gossip = require('ssb-conn/compat')
var ConnScheduler = require('./my-scheduler')

module.exports = [CONN, ConnScheduler, Gossip]

That array is a valid secret-stack plugin which you can .use() in ssb-server.

Why was the gossip plugin refactored? (click here)

The legacy gossip plugin is one of the oldest parts of the SSB stack in Node.js, and it contained several old opinions. It wasn't designed with multiserver in mind, so it made a lot of assumptions that peers have host/port fields. Nowadays with Bluetooth and other unusual modes of connectivity, that assumption breaks down often.

The gossip plugin also did not have the concept of "staging", which is useful for ephemeral connections (LAN or Bluetooth) in spaces that may have many strangers. So the gossip plugin tended to connect as soon as possible to any peer discovered.

Also, since the gossip plugin was a monolith, it had all these concerns (cold persistence, in-memory tracking of current connections, ephemeral peers, scheduling, old and new style addresses) squashed into one file, making it hard and brittle to change the code.

The objectives with CONN were to:

• Untangle the codebase into modular components with single responsibilities
• Standardize the assumption that addresses are always multiserver addresses
• All "pools" (DB, Hub, Staging) are key-value pairs [address, dataObject]
• Make scheduling easily customizable but provide an opinionated default

License

MIT