From b425cb4639e7f69cf0f514fd59322c12881d37a2 Mon Sep 17 00:00:00 2001
From: Fedor Indutny <fedor@indutny.com>
Date: Wed, 14 May 2014 19:24:28 +0400
Subject: [PATCH] pool: proper backoff

---
 lib/bcoin/chain.js | 13 ++++++++-----
 lib/bcoin/pool.js  | 17 +++++++++++++----
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/lib/bcoin/chain.js b/lib/bcoin/chain.js
index e42e207a..fdfb6f75 100644
--- a/lib/bcoin/chain.js
+++ b/lib/bcoin/chain.js
@@ -31,12 +31,16 @@ function Chain(options) {
     bloom: null,
     hashes: [],
     ts: [],
-    heights: []
+    heights: [],
+    lastTs: 0
   };
   this.request = new utils.RequestCache();
 
   this.fromJSON(preload);
 
+  // Last TS after preload, needed for fill percent
+  this.index.lastTs = this.index.ts[this.index.ts.length - 1];
+
   this.loading = false;
   this._init();
 }
@@ -335,10 +339,9 @@ Chain.prototype.isFull = function isFull() {
 };
 
 Chain.prototype.fillPercent = function fillPercent() {
-  var first = this.index.ts[0];
-  var now = (+new Date() / 1000 - 40 * 60) - first;
-  var last = this.index.ts[this.index.ts.length - 1] - first;
-  return Math.min(0, Math.max(last / now, 1));
+  var total = (+new Date() / 1000 - 40 * 60) - this.index.lastTs;
+  var current = this.index.ts[this.index.ts.length - 1] - this.index.lastTs;
+  return Math.min(0, Math.max(current / total, 1));
 };
 
 Chain.prototype.hashesInRange = function hashesInRange(start, end, cb) {
diff --git a/lib/bcoin/pool.js b/lib/bcoin/pool.js
index cf8f4687..94719700 100644
--- a/lib/bcoin/pool.js
+++ b/lib/bcoin/pool.js
@@ -18,6 +18,10 @@ function Pool(options) {
   this.size = options.size || 32;
   this.parallel = options.parallel || 2000;
   this.redundancy = options.redundancy || 2;
+  this.backoff = {
+    delta: options.backoffDelta || 500,
+    max: options.backoffMax || 5000
+  };
   this.load = {
     timeout: options.loadTimeout || 3000,
     interval: options.loadInterval || 5000,
@@ -80,7 +84,7 @@ module.exports = Pool;
 Pool.prototype._init = function _init() {
   this._addLoader();
   for (var i = 0; i < this.size; i++)
-    this._addPeer();
+    this._addPeer(0);
   this._load();
 
   var self = this;
@@ -228,14 +232,14 @@ Pool.prototype._load = function _load() {
   return true;
 };
 
-Pool.prototype._addPeer = function _addPeer() {
+Pool.prototype._addPeer = function _addPeer(backoff) {
   if (this.destroyed)
     return;
   if (this.peers.block.length + this.peers.pending.length >= this.size)
     return;
 
   var peer = new bcoin.peer(this, this.createConnection, {
-    backoff: 750 * Math.random()
+    backoff: backoff
   });
 
   this.peers.pending.push(peer);
@@ -252,7 +256,7 @@ Pool.prototype._addPeer = function _addPeer() {
     self._removePeer(peer);
     if (self.destroyed)
       return;
-    self._addPeer();
+    self._addPeer(Math.max(backoff + self.backoff.delta, self.backoff.max));
   });
 
   peer.once('ack', function() {
@@ -277,8 +281,12 @@ Pool.prototype._addPeer = function _addPeer() {
   });
 
   peer.on('merkleblock', function(block) {
+    // Reset backoff, peer seems to be responsive
+    backoff = 0;
+
     self._response(block);
     self.chain.add(block);
+    self.emit('chain-progress', self.chain.fillPercent());
     self.emit('block', block);
   });
 
@@ -416,6 +424,7 @@ Pool.prototype.search = function search(id, range) {
 
     function done() {
       waiting--;
+      assert(waiting >= 0);
       e.emit('progress', count - waiting, count);
       if (waiting === 0) {
         if (id)