From 8468d3ebd1c96d0781043f1ffc88996e3ef1670f Mon Sep 17 00:00:00 2001
From: Michael Vines <mvines@gmail.com>
Date: Thu, 1 Nov 2018 20:35:19 -0700
Subject: [PATCH] fix: limit concurrent Loads to improve stability

---
 web3.js/src/loader.js | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/web3.js/src/loader.js b/web3.js/src/loader.js
index 6c612b2822..6117d5fee4 100644
--- a/web3.js/src/loader.js
+++ b/web3.js/src/loader.js
@@ -51,7 +51,7 @@ export class Loader {
     const chunkSize = 256;
     let offset = 0;
     let array = data;
-    const transactions = [];
+    let transactions = [];
     while (array.length > 0) {
       const bytes = array.slice(0, chunkSize);
       const userdata = Buffer.alloc(chunkSize + 16);
@@ -71,6 +71,15 @@ export class Loader {
       });
       transactions.push(sendAndConfirmTransaction(this.connection, program, transaction));
 
+      // Run up to 8 Loads in parallel to prevent too many parallel transactions from
+      // getting rejected with AccountInUse.
+      //
+      // TODO: 8 was selected empirically and should probably be revisited
+      if (transactions.length === 8) {
+        await Promise.all(transactions);
+        transactions = [];
+      }
+
       offset += chunkSize;
       array = array.slice(chunkSize);
     }