Refactor BaseConnectionPool empty method

Signed-off-by: Bandini Bhopi <[email protected]>

Author: bandinib-amzn

Diff for: CHANGELOG.md

@@ -18,6 +18,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Bumps `eslint-config-prettier` from 8.8.0 to 9.0.0
 ### Changed
 - Make handling of long numerals an option that is disabled by default ([#557](https://github.com/opensearch-project/opensearch-js/pull/557))
+- Refactor BaseConnectionPool empty method so that callback will always get called even when there is no connection ([#585](https://github.com/opensearch-project/opensearch-js/pull/585)) 
 ### Deprecated
 ### Removed
 ### Fixed

Diff for: lib/pool/BaseConnectionPool.js

@@ -150,13 +150,14 @@ class BaseConnectionPool {
     let openConnections = this.size;
     this.connections.forEach((connection) => {
       connection.close(() => {
-        if (--openConnections === 0) {
-          this.connections = [];
-          this.size = this.connections.length;
-          callback();
-        }
+        openConnections--;
       });
     });
+    if (openConnections === 0) {
+      this.connections = [];
+      this.size = this.connections.length;
+      callback();
+    }
   }
 
   /**