hotfix for unresponsive header sync

lib/services/header/index.js

@@ -14,6 +14,8 @@ var assert = require('assert');
 var constants = require('../../constants');
 var bcoin = require('fcoin');
 
+const SYNC_CHECK_INTERVAL = 1000 * 60 * 15; //15 mins
+
 var HeaderService = function(options) {
 
   BaseService.call(this, options);
@@ -522,6 +524,7 @@ HeaderService.prototype._saveHeaders = function(dbOps, callback) {
 HeaderService.prototype._onHeadersSave = function(callback) {
   var self = this;
 
+  self._syncUnresponsive = false; //SZ: got response from peer
   self._logProgress();
 
   if (!self._syncComplete()) {
@@ -529,6 +532,8 @@ HeaderService.prototype._onHeadersSave = function(callback) {
     return callback();
   }
 
+  clearInterval(self._syncCheckInterval); //SZ: clear the interval check as sync is completed
+
   self._endHeaderSubscription(); // we don't need headers any more
   self._startBlockSubscription(); // we need new blocks coming tu us aynchronuously
 
@@ -707,6 +712,16 @@ HeaderService.prototype._startSync = function() {
     // common case
     if (numNeeded > 0) {
       log.info('Header Service: Gathering: ' + numNeeded + ' ' + 'header(s) from the peer-to-peer network.');
+      
+      //SZ: Adding interval check for sync with peer is responsive or not
+      self._syncUnresponsive = true;
+      self._syncCheckInterval = setInterval(() => {
+        if(self._syncUnresponsive)
+          self._sync();
+        else //reset unresponsive as true
+          self._syncUnresponsive = true;
+      }, SYNC_CHECK_INTERVAL);
+
       return self._sync();
     }