Reproducible local writers

README.md

@@ -62,10 +62,14 @@ Options include:
   map: node => mappedNode, // map nodes before returning them
   reduce: (a, b) => someNode, // reduce the nodes array before returning it
   firstNode: false, // set to true to reduce the nodes array to the first node in it
-  valueEncoding: 'binary' // set the value encoding of the db
+  valueEncoding: 'binary', // set the value encoding of the db
+  localKey: localKeyBuffer, // public key to use for the local writer
+  localSecretKey: localSecretKeyBuffer // secret key to use for the local writer
 }
 ```
 
+The `localKey` and `localSecretKey` options are useful when you need reproducible local writers (for example to recreate a database). If they are not provided, a new key pair will be generated for the local writer. If provided, both keys must be provided together.
+
 #### `db.key`
 
 Buffer containing the public key identifying this hyperdb.

index.js

@@ -65,6 +65,8 @@ function HyperDB (storage, key, opts) {
   this._watching = checkout ? checkout._watching : []
   this._replicating = []
   this._localWriter = null
+  this._localKey = opts.localKey || null
+  this._localSecretKey = opts.localSecretKey || null
   this._byKey = new Map()
   this._heads = opts.heads || null
   this._version = opts.version || null
@@ -582,7 +584,7 @@ HyperDB.prototype._ready = function (cb) {
   this.source.ready(function (err) {
     if (err) return done(err)
     if (self.source.writable) self.local = self.source
-    if (!self.local) self.local = feed('local')
+    if (!self.local) self.local = feed('local', self._localKey, { secretKey: self._localSecretKey })
 
     self.key = self.source.key
     self.discoveryKey = self.source.discoveryKey

test/basic.js

@@ -4,6 +4,23 @@ var Readable = require('stream').Readable
 var create = require('./helpers/create')
 var run = require('./helpers/run')
 
+tape('reproducible local hypercore', function (t) {
+  var key = Buffer.from('de14f28853123596830410a371b38bd4768fcb95880142e9e54a00aa8c418158', 'hex')
+  var localKey = Buffer.from('c575d78d42d42b88db80c3b66ba6cacdb0e633f98e375226b23788c5d5dd4a17', 'hex')
+  var localSecretKey = Buffer.from('778e1ed4513175ebac7cfcc97dbde5bd87795c990811784e85de0abc3b2da36ac575d78d42d42b88db80c3b66ba6cacdb0e633f98e375226b23788c5d5dd4a17', 'hex')
+
+  var db = create.one(key, {
+    localKey,
+    localSecretKey
+  })
+
+  db.on('ready', function () {
+    t.same(db.local.key, localKey)
+    t.same(db.local.secretKey, localSecretKey)
+    t.end()
+  })
+})
+
 tape('basic put/get', function (t) {
   var db = create.one()
   db.put('hello', 'world', function (err, node) {