From d616487b881774cdfb85d821e22b4108102df8f2 Mon Sep 17 00:00:00 2001
From: Russ Tyndall <russ@acceleration.net>
Date: Wed, 29 Mar 2017 16:07:26 -0400
Subject: [PATCH] Prevent permanent waits from destroyed workers

Prevent permanent waits, by ensuring that we continue creating
resources if we need them

 * There are many errors due to pools being configured with min: 0
   but then running out of workers while there is still work to do
 * This results in missed work, infinite loops and timeouts
 * A solution is to ensure that if we still have work todo
   that we make sure we still have some workers to do them

See:

 * https://github.com/brianc/node-pg-pool/issues/48
 * https://github.com/strongloop/loopback-connector-postgresql/issues/231
 * https://github.com/coopernurse/node-pool/issues/175 (Seems related)
---
 lib/Pool.js | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/lib/Pool.js b/lib/Pool.js
index f60a70e6..54b02f2c 100644
--- a/lib/Pool.js
+++ b/lib/Pool.js
@@ -302,11 +302,18 @@ class Pool extends EventEmitter {
    */
   _ensureMinimum () {
     if (this._draining === true) {
-      return
+      return;
+    }
+    const minShortfall = this._config.min - this._count;
+
+    if(minShortfall == 0){
+      const waiting  = this._waitingClientsQueue.size();
+      if(waiting > 0){
+        minShortFall = diff = Math.min(waiting, this._config.max - this._count);
+      }
     }
-    const minShortfall = this._config.min - this._count
     for (let i = 0; i < minShortfall; i++) {
-      this._createResource()
+      this._createResource();
     }
   }