replicatable.js

function create (path)
  var db = require('levelup')(path, {createIfMissing: true})
  var Replicator = require('level-replicator')
  var replicator = Replicator(db, {
    prefix:'replicateable',
    merge: function (oldVal, newVal) {
      if(!oldVal) return newVal
      //handle the differences between old and new,
      //the user is expected to implement some version system,
      //and store that data in the object...
      //vector clocks, or couchdb style hash pointers are good options.
      if(illegalUpdate(oldVal, newVal)) throw new Error('invalid')

      return merge(oldVal, newVal)
    }
  })
  return replicator
}

var a = create('/tmp/A')
var b = create('/tmp/B')
var as = a.createStream()

as.pipe(b.createStream()).pipe(as)

a.put(key, value)

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