Awesome

SSB partial replication

A collection of functions useful for replicating a part of the log instead of everything. This is superseeded by SSB secure partial replication.

api

getFeed({id: feedId, seq: int?, live: bool?, limit: int?, keys: bool?, values: bool?}) -> PullSource

The method has exactly the same interface as createHistoryStream because it just wraps the function. It is much faster though. See appendix for more information.

getFeedReverse({id: feedId, seq: int?, live: bool?, limit: int?, keys: bool?, values: bool?}) -> PullSource

This function does the same as getFeed except if one does not specify seq the latest sequence for the feed with be fetched and used. This allows one to get the latest X messages from a feed using the limit option without knowing how many messages the feed currently has.

getTangle(msgId, cb)

Get all the messages of a tangle given a root message id. This can be used to fetch threads or similar tangles. This is similar in spirit to ssb-ooo except there is no protocol involved to fetch messages from other nodes.

getMessagesOfType({id: feedId, type: string, seq: int?, limit: int?}) -> PullSource

Get messages of a particular type for a feed. This can be used to fetch say all contact messages for a particular feed to construct the social graph without having to download all the messages of the feed.

Appendix

There is something wrong with createHistoryStream over a network connection. Locally it takes around 600ms, using net protocol the same call takes 6.500ms and using ws the exact same call takes 20.000ms?

var pull = require('pull-stream')

var remote = 'ws:between-two-worlds.dk:8989~shs:lbocEWqF2Fg6WMYLgmfYvqJlMfL7hiqVAV6ANjHWNw8=.ed25519'
//remote = 'net:between-two-worlds.dk:8008~shs:lbocEWqF2Fg6WMYLgmfYvqJlMfL7hiqVAV6ANjHWNw8=.ed25519'

require('ssb-client')({ remote }, (err, sbot) => {
  if (err) throw err
  console.time("downloading messages")
  pull(
    sbot.createHistoryStream({id: '@ye+QM09iPcDJD6YvQYjoQc7sLF/IFhmNbEqgdzQo3lQ=.ed25519', seq: 27000, keys: false}),
    pull.drain((msg) => {
      console.log(msg)
    }, (err) => {
      if (err) throw err

      console.timeEnd("downloading messages")
      sbot.close()
    })
  )
})

The problem seems to be buried in the legacy protocol for ssb-replication somewhere.

This module simply exposes createHistoryStream as partialReplication without any of the legacy overhead and we are back to 600ms again.