Don't count idle connections against maxTotal

core/src/main/scala/org/typelevel/keypool/KeyPool.scala

@@ -295,11 +295,19 @@ object KeyPool {
           }
       }
 
+    def createWithPermit: Resource[F, B] =
+      kp.kpMaxTotalSem.tryPermit.flatMap {
+        case true =>
+          kp.kpRes(k)
+        case false =>
+          ApplicativeThrow[Resource[F, *]].raiseError(
+            new NoSuchElementException("Pool is maxed out on idle connections for other keys"))
+      }
+
     for {
-      _ <- kp.kpMaxTotalSem.permit
       optR <- Resource.eval(kp.kpVar.modify(go))
       releasedState <- Resource.eval(Ref[F].of[Reusable](kp.kpDefaultReuseState))
-      resource <- Resource.make(optR.fold(kp.kpRes(k).allocated)(r => Applicative[F].pure(r))) {
+      resource <- Resource.make(optR.fold(createWithPermit.allocated)(r => Applicative[F].pure(r))) {
         resource =>
           for {
             reusable <- releasedState.get

core/src/test/scala/org/typelevel/keypool/KeyPoolSpec.scala

@@ -176,7 +176,29 @@ class KeyPoolSpec extends CatsEffectSuite {
       }
   }
 
+  test("Do not count idle resources toward maxTotal".only) {
+    final case class Stats(active: Int, highWater: Int) {
+      def inc =
+        copy(active = active + 1, highWater = math.max(active + 1, highWater))
+      def dec =
+        copy(active = active - 1)
+    }
+    IO.ref(Stats(0, 0)).flatMap(active =>
+      KeyPool.Builder((i: Int) =>
+          Resource.make(active.update(_.inc))(i => active.update(_.dec)))
+        .withMaxTotal(5)
+        .withMaxIdle(5)
+        .build
+        .use(keypool =>
+          keypool.take(0).replicateA(5).use_ *>
+          keypool.take(1).replicateA(5).use_
+        )
+        .flatMap(_ => active.get.map(_.highWater))
+        .flatTap(IO.println)
+    )
+    .map(i => assert(i <= 5, s"Active connections maxed out at $i"))
+  }
+
   private def nothing(ref: Ref[IO, Int]): IO[Unit] =
     ref.get.void
-
 }