From e3b96a2d3285fd2fca346307f4ad75948a37b14e Mon Sep 17 00:00:00 2001
From: Chris Kleeschulte <chrisk@bitpay.com>
Date: Wed, 9 Aug 2017 11:48:00 -0400
Subject: [PATCH] Paired down what information we are persisting as far as
 headers go.

---
 lib/services/header/index.js | 43 ++++++++++++++++++++++++++----------
 1 file changed, 31 insertions(+), 12 deletions(-)

diff --git a/lib/services/header/index.js b/lib/services/header/index.js
index 3040437b..fc6cbda2 100644
--- a/lib/services/header/index.js
+++ b/lib/services/header/index.js
@@ -116,8 +116,8 @@ HeaderService.prototype.start = function(callback) {
 
         self._db._store.put(self._encoding.encodeHeaderKey(0, self.GENESIS_HASH),
           self._encoding.encodeHeaderValue(genesisHeader), next);
-
         return;
+
       }
       next();
     },
@@ -190,7 +190,7 @@ HeaderService.prototype._onBlock = function(block) {
   }
 
   for (var i = 0; i < this.subscriptions.block.length; i++) {
-    this.subscriptions.block[i].emit('header/block', block);
+    this.subscriptions.block[i].emit('header/block', block, header);
   }
 };
 
@@ -198,44 +198,57 @@ HeaderService.prototype._onHeaders = function(headers) {
 
   var self = this;
 
+
   log.debug('Header Service: Received: ' + headers.length + ' header(s).');
 
-  var prevHeader = self._headers.getLastIndex();
-
   var dbOps = [];
+
   for(var i = 0; i < headers.length; i++) {
+
     var header = headers[i];
     if (header instanceof Header) {
       header = header.toObject();
     }
+
     header.height = ++self._tip.height;
+    header.chainwork = self._getChainwork(header).toString(16, 64);
+    self._lastChainwork = header.chainwork;
+
     self._tip.hash = header.hash;
-    header.chainwork = self._getChainwork(header, prevHeader).toString(16, 64);
+
     dbOps.push({
       type: 'put',
       key: self._encoding.encodeHeaderKey(header.height, header.hash),
       value: self._encoding.encodeHeaderValue(header)
     });
-    prevHeader = header;
-    self._headers.set(header.hash, header, header.height);
+
+    var newHdr = { hash: header.hash, prevHash: header.prevHash, height: header.height };
+    self._headers.set(header.hash, newHdr, header.height);
+
   }
 
   var tipOps = utils.encodeTip(self._tip, self.name);
+
   dbOps.push({
     type: 'put',
     key: tipOps.key,
     value: tipOps.value
   });
 
-  self._db.batch(dbOps, function() {
+  self._db.batch(dbOps, function(err) {
+
+    if(err) {
+      log.error(err);
+      this.node.stop();
+      return;
+    }
 
     if (self._tip.height < self._bestHeight) {
       self._sync();
       return;
     }
 
-    log.info('Header Service: ' + self._headers.size - 1 + ' headers downloaded and persisted.');
-    log.info('Header Service: ' + self._headers.getLastIndex().hash + ' is the best block hash.');
+    log.debug('Header Service: ' + self._headers.getLastIndex().hash + ' is the best block hash.');
 
     // at this point, we can check our header list to see if our starting tip diverged from the tip
     // that we have now
@@ -310,9 +323,11 @@ HeaderService.prototype._getPersistedHeaders = function(callback) {
   var self = this;
 
   var startingHeight = self._tip.height;
+
   if (self._tip.height > self._checkpoint) {
     self._tip.height -= self._checkpoint;
   }
+
   var removalOps = [];
 
   var start = self._encoding.encodeHeaderKey(0);
@@ -335,6 +350,7 @@ HeaderService.prototype._getPersistedHeaders = function(callback) {
   stream.on('data', function(data) {
     var header  = self._encoding.decodeHeaderValue(data.value);
     // any records with a height greater than our current tip height can be scheduled for removal
+    // because they will be replaced shortly
     if (header.height > self._tip.height) {
       removalOps.push({
         type: 'del',
@@ -350,6 +366,10 @@ HeaderService.prototype._getPersistedHeaders = function(callback) {
       return streamErr;
     }
     self._tip.hash = self._headers.getIndex(self._tip.height).hash;
+    var lastHeader = self._headers.getLastIndex();
+    if (lastHeader && lastHeader.chainwork) {
+      self._lastChainwork = lastHeader.chainwork;
+    }
     self._db.batch(removalOps, callback);
   });
 
@@ -357,8 +377,7 @@ HeaderService.prototype._getPersistedHeaders = function(callback) {
 
 HeaderService.prototype._getChainwork = function(header, prevHeader) {
 
-  var lastChainwork = prevHeader ? prevHeader.chainwork : HeaderService.STARTING_CHAINWORK;
-  var prevChainwork = new BN(new Buffer(lastChainwork, 'hex'));
+  var prevChainwork = new BN(new Buffer(this._lastChainwork || HeaderService.STARTING_CHAINWORK, 'hex'));
 
   return this._computeChainwork(header.bits, prevChainwork);
 };