From cd88f2ad1bd3ca73cfb7c4c87172a3af64c53393 Mon Sep 17 00:00:00 2001
From: Nicolas Gotchac <ngotchac@gmail.com>
Date: Wed, 23 Nov 2016 19:12:32 +0100
Subject: [PATCH] Don't fetch balances on every new block if syncing #3582

---
 js/src/redux/providers/balances.js      | 28 +++++++++++++++++++++++++
 js/src/redux/providers/statusReducer.js |  2 +-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/js/src/redux/providers/balances.js b/js/src/redux/providers/balances.js
index bcc8eca0a..c0260ba71 100644
--- a/js/src/redux/providers/balances.js
+++ b/js/src/redux/providers/balances.js
@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
+import { throttle } from 'lodash';
+
 import { getBalances, getTokens } from './balancesActions';
 import { setAddressImage } from './imagesActions';
 
@@ -37,11 +39,20 @@ export default class Balances {
 
     this._accountsInfo = null;
     this._tokenreg = null;
+    this._fetchingBalances = false;
     this._fetchingTokens = false;
     this._fetchedTokens = false;
 
     this._tokenregSubId = null;
     this._tokenregMetaSubId = null;
+
+    // Throttled `retrieveTokens` function
+    // that gets called max once every 20s
+    this._throttledRetrieveTokens = throttle(
+      this._retrieveTokens,
+      20 * 1000,
+      { trailing: true }
+    );
   }
 
   start () {
@@ -72,6 +83,15 @@ export default class Balances {
           return console.warn('_subscribeBlockNumber', error);
         }
 
+        const { syncing } = this._store.getState().nodeStatus;
+
+        // If syncing, only retrieve balances once every
+        // few seconds
+        if (syncing) {
+          return this._throttledRetrieveTokens();
+        }
+
+        this._throttledRetrieveTokens.cancel();
         this._retrieveTokens();
       })
       .catch((error) => {
@@ -140,10 +160,16 @@ export default class Balances {
   }
 
   _retrieveBalances () {
+    if (this._fetchingBalances) {
+      return;
+    }
+
     if (!this._accountsInfo) {
       return;
     }
 
+    this._fetchingBalances = true;
+
     const addresses = Object
       .keys(this._accountsInfo)
       .filter((address) => {
@@ -161,9 +187,11 @@ export default class Balances {
         });
 
         this._store.dispatch(getBalances(this._balances));
+        this._fetchingBalances = false;
       })
       .catch((error) => {
         console.warn('_retrieveBalances', error);
+        this._fetchingBalances = false;
       });
   }
 
diff --git a/js/src/redux/providers/statusReducer.js b/js/src/redux/providers/statusReducer.js
index 07fa993b9..f0ef0cb1b 100644
--- a/js/src/redux/providers/statusReducer.js
+++ b/js/src/redux/providers/statusReducer.js
@@ -39,7 +39,7 @@ const initialState = {
   },
   netPort: new BigNumber(0),
   rpcSettings: {},
-  syncing: false,
+  syncing: true,
   isConnected: false,
   isConnecting: false,
   isPingable: false,