Added internal _closing flag in connection object

Author: cjbj

lib/connection.js

@@ -172,7 +172,20 @@ async function close(a1) {
     nodbUtil.assert(nodbUtil.isObject(a1), 'NJS-005', 1);
     options = a1;
   }
-  await this._close(options);
+
+  // If already in the process of closing, throw an error instead of doing
+  // a roundtrip
+  if (this._closing) {
+    throw new Error (nodbUtil.getErrorMessage('NJS-003'));
+  }
+
+  this._closing = true;
+  try {
+    await this._close(options);
+  } finally {
+    this._closing = false;
+  }
+
   for (const cls of Object.values(this._dbObjectClasses)) {
     cls.prototype.constructor = Object;
     cls.prototype = null;
@@ -461,6 +474,7 @@ class Connection extends EventEmitter {
     this._dbObjectClasses = {};
     this._requestQueue = [];
     this._inProgress = false;
+    this._closing = false;
   }
 
   // extend class with promisified functions
@@ -548,7 +562,7 @@ class Connection extends EventEmitter {
   //        This is a synchronous call.
   //---------------------------------------------------------------------------
   isHealthy() {
-    return this._isHealthy();
+    return (!this._closing && this._isHealthy());
   }