From 8a9babaf7724847748529bc53a2aba8d25df0f3f Mon Sep 17 00:00:00 2001
From: Steve Cresswell <229672+cressie176@users.noreply.github.com>
Date: Thu, 10 Aug 2023 23:59:15 +0100
Subject: [PATCH] Expose queue depth and pending resources in stats

---
 lib/Pool.js       |  6 +++---
 test/Pool.test.js | 20 +++++++++++++++++++-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/lib/Pool.js b/lib/Pool.js
index 2cc0e1b..00c13d7 100644
--- a/lib/Pool.js
+++ b/lib/Pool.js
@@ -74,8 +74,8 @@ module.exports = class Pool extends EventEmitter {
   }
 
   stats() {
-    const { size, idle, acquired, bad, pending, available } = this._resourceStore;
-    return { size, idle, acquired, bad, available, pending };
+    const { size, idle, pending, acquired, bad, available } = this._resourceStore;
+    return { size, idle, queued: this._acquireQueue.length, pending, acquired, bad, available };
   }
 
   async shutdown() {
@@ -154,7 +154,7 @@ module.exports = class Pool extends EventEmitter {
   }
 
   _checkAcquireQueue() {
-    debug('[%d] Checking acquire queue', getContextId());
+    debug('[%d] Checking acquire queue (%d)', getContextId(), this._acquireQueue.length);
     if (this._acquireQueue.length === 0) return debug('[%d] Acquire queue is empty', getContextId());
     if (this._resourceStore.isExhausted()) return debug('[%d] Pool is exhausted', getContextId());
     const { resolve } = this._acquireQueue.shift();
diff --git a/test/Pool.test.js b/test/Pool.test.js
index 75dc6a4..2d05902 100644
--- a/test/Pool.test.js
+++ b/test/Pool.test.js
@@ -621,9 +621,11 @@ describe('Pool', () => {
         const factory = new TestFactory();
         const pool = createPool({ factory });
 
-        const { size, idle, acquired, bad, available } = pool.stats();
+        const { size, idle, queued, pending, acquired, bad, available } = pool.stats();
         eq(size, 0);
         eq(idle, 0);
+        eq(queued, 0);
+        eq(pending, 0);
         eq(acquired, 0);
         eq(bad, 0);
         eq(available, Infinity);
@@ -660,6 +662,22 @@ describe('Pool', () => {
         eq(available, Infinity);
       });
 
+      it('should report stats for a pool with queued acquisition requests', async () => {
+        const resources = ['R1'];
+        const factory = new TestFactory(resources);
+        const pool = createPool({ factory, maxSize: 1 });
+
+        await pool.acquire();
+        pool.acquire();
+        pool.acquire();
+
+        const { size, idle, queued, acquired } = pool.stats();
+        eq(size, 1);
+        eq(idle, 0);
+        eq(queued, 2);
+        eq(acquired, 1);
+      });
+
       it('should report stats for a pool with bad resources', async (t, done) => {
         const resources = ['R1', { destroyError: 'Oh Noes!', value: 'R2' }, 'R3'];
         const factory = new TestFactory(resources);