From 6dc3f2dd6f492eb2d9354084cfe5ea00155b07e8 Mon Sep 17 00:00:00 2001
From: Stephen von Takach <steve@vontaka.ch>
Date: Tue, 7 Sep 2021 08:02:43 +1000
Subject: [PATCH] fix(pool): returning closed resources to the pool (#154)

---
 spec/pool_spec.cr | 17 +++++++++++++++++
 src/db/pool.cr    |  4 +++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/spec/pool_spec.cr b/spec/pool_spec.cr
index 6a1612c..9aed907 100644
--- a/spec/pool_spec.cr
+++ b/spec/pool_spec.cr
@@ -190,6 +190,23 @@ describe DB::Pool do
     all[2].closed?.should be_false
   end
 
+  it "should not return closed resources to the pool" do
+    pool = DB::Pool.new(max_pool_size: 1, max_idle_pool_size: 1) { Closable.new }
+
+    # pool size 1 should be reusing the one resource
+    resource1 = pool.checkout
+    pool.release resource1
+    resource2 = pool.checkout
+    resource1.should eq resource2
+
+    # it should not return a closed resource to the pool
+    resource2.close
+    pool.release resource2
+
+    resource2 = pool.checkout
+    resource1.should_not eq resource2
+  end
+
   it "should create resource after max_pool was reached if idle forced some close up" do
     all = [] of Closable
     pool = DB::Pool.new(max_pool_size: 3, max_idle_pool_size: 1) { Closable.new.tap { |c| all << c } }
diff --git a/src/db/pool.cr b/src/db/pool.cr
index e483dd8..5964de8 100644
--- a/src/db/pool.cr
+++ b/src/db/pool.cr
@@ -141,7 +141,9 @@ module DB
       idle_pushed = false
 
       sync do
-        if can_increase_idle_pool
+        if resource.responds_to?(:closed?) && resource.closed?
+          @total.delete(resource)
+        elsif can_increase_idle_pool
           @idle << resource
           if resource.responds_to?(:after_release)
             resource.after_release