multi-writer hypercore using corestore and networker
npm install hypermultifeed
var Multifeed = require('multifeed')
var ram = require('random-access-memory')
var multi = new Multifeed('./db', { valueEncoding: 'json' })
// a multifeed starts off empty
console.log(multi.feeds().length) // => 0
// create as many writeable feeds as you want; returns hypercores
multi.writer('local', function (err, w) {
console.log(w.key, w.writeable, w.readable) // => Buffer <0x..> true true
console.log(multi.feeds().length) // => 1
// write data to any writeable feed, just like with hypercore
w.append('foo', function () {
var m2 = multifeed(hypercore, ram, { valueEncoding: 'json' })
m2.writer('local', function (err, w2) {
w2.append('bar', function () {
replicate(multi, m2, function () {
console.log(m2.feeds().length) // => 2
m2.feeds()[1].get(0, function (_, data) {
console.log(data) // => foo
})
multi.feeds()[1].get(0, function (_, data) {
console.log(data) // => bar
})
})
})
})
})
})
function replicate (a, b, cb) {
let pending = 2
var r = a.replicate()
r.pipe(b.replicate()).pipe(r)
.once('error', cb)
.once('remote-feeds', done)
.once('remote-feeds', done)
function done () {
if (!--pending) return cb()
}
}
`
$3
`
const Corestore = require('corestore')
const SwarmNetworker = require('corestore-swarm-networking')
const Multifeed = require('multifeed')
const Networker = require('multifeed/networker')
const crypto = require('hypercore-crypto')
// create a new corestore for our hypercores
const corestore = new Corestore(ram)
// initialize hyperswarm using corestore-swarm-networker and configure for multifeed
const network = new Networker(new SwarmNetworker(corestore))
// create two separate instances of multifeed for use across a single network swarm
const multi1 = new Multifeed(corestore, { key: crypto.randomBytes(32) })
const multi2 = new Multifeed(corestore, { key: crypto.randomBytes(32) })
// start replicating
network.swarm(multi1)
network.swarm(multi2)
// create a third instance which shares a key with the first
const multi3 = new Multifeed(corestore, { key: multi1.key })
// multi1 and multi3 will now replicate feeds
network.swarm(multi3)
`
For more information on how to implement replication across multiple multifeeds, see test/new-basic.js for an example.
The main export (new Multifeed(storage, opts)) is API compatible with the original Multifeed as documented below. storage can also be a corestore (otherwise one is created with storage). Then connect it to a corestore swarm networker to apply multifeed replication.
API
`js
var multifeed = require('multifeed')
`
$3
Pass in a random-access-storage backend, and options. Included opts are passed into new hypercores created, and are the same as hypercore's.
Valid opts include:
- opts.encryptionKey (string): optional encryption key to use during replication. If not provided, a default insecure key will be used.
- opts.hypercore: constructor of a hypercore implementation. hypercore@8.x.x is used from npm if not provided.
$3
If no name is given, a new local writeable feed is created and returned via
cb.
If name is given and was created in the past on this local machine, it is
returned. Otherwise it is created. This is useful for managing multiple local
feeds, e.g.
`js
var main = multi.writer('main') // created if doesn't exist
var content = multi.writer('content') // created if doesn't exist
main === multi.writer('main') // => true
`
options is an optional object which may contain:
- options.keypair - an object with a custom keypair for the new writer. This should have properties keypair.publicKey and keypair.secretKey, both of which should be buffers.
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An array of all hypercores in the multifeed. Check a feed's key to
find the one you want, or check its writable / readable properties.
Only populated once multi.ready(fn) is fired.
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Fetch a feed by its key key (a Buffer or hex string).
$3
Create an encrypted duplex stream for replication.
Ensure that isInitiator to true to one side, and false on the other. This is necessary for setting up the encryption mechanism.
Works just like hypercore, except all local hypercores are exchanged between
replication endpoints.
$3
Emitted when a new batch (1 or more) of remote feeds have begun to replicate with this multifeed instance.
This is useful for knowing when multi.feeds() contains the full set of feeds from the remote side.
$3
Emitted whenever a new feed is added, whether locally or remotely.
multi.close(cb)
Close all file resources being held by the multifeed instance. cb is called once this is complete.
multi.closed
true if close() was run successfully, falsey otherwise.
Errors
The duplex stream returned by .replicate() can emit, in addition to regular
stream errors, two fatal errors specific to multifeed:
- ERR_VERSION_MISMATCH
- err.code = 'ERR_VERSION_MISMATCH'
- err.usVersion = 'X.Y.Z' (semver)
- err.themVersion = 'A.B.C' (semver)
- ERR_CLIENT_MISMATCH
- err.code = 'ERR_CLIENT_MISMATCH'
- err.usClient = 'MULTIFEED'
- err.themClient = '???'
Install
With npm installed, run
`
$ npm install @frando/corestore-multifeed
``