hotfix: block subscription getting stuck

- Issue: Block subscription getting stuck when a (missing) block wasn't received by block service.
- Solution: Re-trigger the sync process when too many blocks ignored

- Others: fixed a typo in _reportInterval property

lib/services/block/index.js

@@ -13,6 +13,8 @@ var bcoin = require('fcoin');
 var _ = require('lodash');
 var LRU = require('lru-cache');
 
+const MAX_IGNORED_BLOCK = 32; //Maximum ignored block allowed before trigging sync again
+
 var BlockService = function(options) {
 
   BaseService.call(this, options);
@@ -637,6 +639,7 @@ BlockService.prototype._startBlockSubscription = function() {
   }
 
   this._subscribedBlock = true;
+  this._ignoredBlockCount = 0; //SZ: reset the ignored count to 0 when subscription starts
 
   log.info('Block Service: starting p2p block subscription.');
   this._bus.on('p2p/block', this._queueBlock.bind(this));
@@ -938,6 +941,15 @@ BlockService.prototype._processBlock = function(block, callback) {
     return self._saveBlock(block, callback);
   }
 
+  //SZ: count the ignored blocks. if many blocks ignored, trigger sync process
+  if(self._ignoredBlockCount < MAX_IGNORED_BLOCK)
+    self._ignoredBlockCount++;
+  else {
+    self._ignoredBlockCount = 0;
+    self._removeAllSubscriptions();
+    self._startSync();
+  }
+
   // reorg -- in this case, we will not handle the reorg right away
   // instead, we will skip the block and wait for the eventual call to
   // "onHeaders" function. When the header service calls this function,
@@ -953,6 +965,7 @@ BlockService.prototype._saveBlock = function(block, callback) {
 
   var self = this;
   block.__height = self._tip.height + 1;
+  self._ignoredBlockCount = 0; //SZ: a block is saved, reset the ignored count
 
   var services = self.node.services;
 
@@ -1097,7 +1110,7 @@ BlockService.prototype._startSync = function() {
     this.on('next block', this._sync.bind(this));
     this.on('synced', this._onSynced.bind(this));
     clearInterval(this._reportInterval);
-    this._reportingInterval = setInterval(this._logProgress.bind(this), 5000);
+    this._reportInterval = setInterval(this._logProgress.bind(this), 5000);
     return this._sync();
   }