From a04a9586894e1a64fd7514161b3c0bfd5291e5bf Mon Sep 17 00:00:00 2001
From: nodkz <pavel.chertorogov@gmail.com>
Date: Tue, 6 Jun 2017 22:06:25 +0600
Subject: [PATCH] fix(Concurrency): Multiple databases start ups in serial.

This fix avoid parallel download of mongod binaries.
---
 src/index.js | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/index.js b/src/index.js
index 5edb31abc..52f6e889c 100644
--- a/src/index.js
+++ b/src/index.js
@@ -33,6 +33,7 @@ async function generateConnectionString(port: number, dbName: ?string): Promise<
 }
 
 export default class MongoDBMemoryServer {
+  static mongodHelperStartup: ?Promise<any>;
   isRunning: boolean = false;
   runningInstance: ?Promise<MongoInstanceDataT>;
   opts: MongoMemoryServerOptsT;
@@ -111,9 +112,15 @@ export default class MongoDBMemoryServer {
 
     mongodCli.debug.enabled = this.opts.debug;
 
+    if (this.constructor.mongodHelperStartup) {
+      await this.constructor.mongodHelperStartup;
+    }
+
     // Download if not exists mongo binaries in ~/.mongodb-prebuilt
     // After that startup MongoDB instance
-    await mongodCli.run();
+    const startupPromise = mongodCli.run();
+    this.constructor.mongodHelperStartup = startupPromise;
+    await startupPromise;
 
     data.mongodCli = mongodCli;
     data.tmpDir = tmpDir;