feat: allow control over uploading to peers

Partial fix to holepunchto#305

index.js

@@ -402,6 +402,7 @@ module.exports = class Hypercore extends EventEmitter {
 
     this.replicator = new Replicator(this.core, this.key, {
       eagerUpgrade: true,
+      defaultUploading: opts.defaultUploading,
       notDownloadingLinger: opts.notDownloadingLinger,
       allowFork: opts.allowFork !== false,
       inflightRange: opts.inflightRange,

lib/replicator.js

@@ -358,9 +358,17 @@ class Peer {
     this.lastExtensionSent = ''
     this.lastExtensionRecv = ''
 
+    this.uploading = this.replicator.defaultUploading
+
     replicator._ifAvailable++
   }
 
+  setUploading (uploading) {
+    if (uploading === this.uploading) return
+    this.uploading = uploading
+    this.sendSync()
+  }
+
   get remoteContiguousLength () {
     return this.remoteBitfield.findFirst(false, this._remoteContiguousLength)
   }
@@ -418,7 +426,7 @@ class Peer {
       length: this.core.tree.length,
       remoteLength: this.core.tree.fork === this.remoteFork ? this.remoteLength : 0,
       canUpgrade: this.canUpgrade,
-      uploading: true,
+      uploading: this.uploading,
       downloading: this.replicator.isDownloading(),
       hasManifest: !!this.core.header.manifest && this.core.compat === false
     })
@@ -646,6 +654,12 @@ class Peer {
       return
     }
 
+    // Respond to manifest requests even if not uploading
+    if (!this.uploading && proof.block) {
+      this.wireNoData.send({ request: msg.id })
+      return
+    }
+
     if (proof.block !== null) {
       this.replicator.onupload(proof.block.index, proof.block.value, this)
     }
@@ -772,6 +786,7 @@ class Peer {
   }
 
   onwant ({ start, length }) {
+    if (!this.uploading) return
     this.replicator._onwant(this, start, length)
   }
 
@@ -1042,6 +1057,9 @@ class Peer {
       return false
     }
 
+    // Send maybeWant before checking this?
+    if (!this.remoteUploading) return false
+
     if (!this._hasTreeParent(b.index)) {
       return false
     }
@@ -1058,6 +1076,7 @@ class Peer {
   }
 
   _requestRangeBlock (index, length) {
+    if (!this.remoteUploading) return false
     if (this.core.bitfield.get(index) === true || !this._hasTreeParent(index)) return false
 
     const b = this.replicator._blocks.add(index, PRIORITY.NORMAL)
@@ -1093,6 +1112,7 @@ class Peer {
   }
 
   _requestRange (r) {
+    if (!this.remoteUploading) return false
     const { length, fork } = this.core.tree
 
     if (r.blocks) {
@@ -1152,6 +1172,7 @@ class Peer {
   }
 
   _requestForkRange (f) {
+    if (!this.remoteUploading) return false
     if (f.fork !== this.remoteFork || f.batch.want === null) return false
 
     const end = Math.min(f.batch.want.end, this.remoteLength)
@@ -1243,6 +1264,7 @@ module.exports = class Replicator {
 
   constructor (core, key, {
     notDownloadingLinger = NOT_DOWNLOADING_SLACK,
+    defaultUploading = true,
     eagerUpgrade = true,
     allowFork = true,
     inflightRange = null,
@@ -1264,6 +1286,7 @@ module.exports = class Replicator {
     this.findingPeers = 0 // updateable from the outside
     this.destroyed = false
     this.downloading = false
+    this.defaultUploading = defaultUploading // should peers default to uploading
     this.activeSessions = 0
 
     this.inflightRange = inflightRange || DEFAULT_MAX_INFLIGHT

test/replicate.js

@@ -745,6 +745,73 @@ test.skip('can disable downloading from a peer', async function (t) {
   t.is(cUploads, a.length)
 })
 
+test('can disable uploading to a peer', async function (t) {
+  const a = await create({ defaultUploading: false })
+
+  await a.append(['a', 'b', 'c', 'd', 'e'])
+
+  const b = await create(a.key, { valueEncoding: 'utf-8' })
+  const c = await create(a.key, { valueEncoding: 'utf-8' })
+
+  const [bStream] = replicate(a, b, t)
+  const [cStream] = replicate(a, c, t)
+  replicate(b, c, t)
+
+  await new Promise(resolve => a.on('peer-add', function onAdd () {
+    if (a.peers.length < 2) return
+    a.off('peer-add', onAdd)
+    resolve()
+  }))
+
+  let aUploadsToB = 0
+  let aUploadsToC = 0
+
+  a.on('upload', function (index, block, peer) {
+    if (peer.remotePublicKey.equals(bPeer.remotePublicKey)) {
+      aUploadsToB++
+    } else {
+      aUploadsToC++
+    }
+  })
+
+  await Promise.all([
+    b.update({ wait: true }),
+    c.update({ wait: true })
+  ])
+
+  t.is(a.length, b.length)
+  t.is(a.length, c.length)
+
+  const bPeer = a.peers[0].stream.rawStream === bStream
+    ? a.peers[0]
+    : a.peers[1]
+  const cPeer = a.peers[0].stream.rawStream === cStream
+    ? a.peers[0]
+    : a.peers[1]
+
+  const cRange = c.download({ start: 0, end: a.length })
+  const bRange = b.download({ start: 0, end: a.length })
+
+  await new Promise(resolve => setTimeout(resolve, 200))
+
+  t.is(b.contiguousLength, 0)
+  t.is(c.contiguousLength, 0)
+  t.is(aUploadsToB, 0)
+  t.is(aUploadsToC, 0)
+
+  cPeer.setUploading(true)
+
+  await Promise.all([
+    bRange.done(),
+    cRange.done()
+  ])
+
+  t.is(b.contiguousLength, 5)
+  t.is(c.contiguousLength, 5)
+  t.is(aUploadsToB, 0)
+  t.is(aUploadsToC, 5)
+})
+
 test('contiguous length', async function (t) {
   const a = await create()