Merge pull request processout#8 from processout/improve-max-duration-…

…comments

Improve maximum duration logic comments & more test

pool.go

@@ -189,7 +189,12 @@ func (c *ClientConn) Close() error {
 	if c.pool.IsClosed() {
 		return ErrClosed
 	}
-	// If the wrapper connection has become too old, we want to recycle it
+	// If the wrapper connection has become too old, we want to recycle it. To
+	// clarify the logic: if the sum of the initialization time and the max
+	// duration is before Now(), it means the initialization is so old adding
+	// the maximum duration couldn't put in the future. This sum therefore
+	// corresponds to the cut-off point: if it's in the future we still have
+	// time, if it's in the past it's too old
 	maxDuration := c.pool.maxLifeDuration
 	if maxDuration > 0 && c.timeInitiated.Add(maxDuration).Before(time.Now()) {
 		c.Unhealthy()

pool_test.go

@@ -139,4 +139,26 @@ func TestMaxLifeDuration(t *testing.T) {
 	if !c.unhealthy {
 		t.Errorf("the connection should've been marked as unhealthy")
 	}
+
+	// Let's also make sure we don't prematurely close the connection
+	p, err = New(func() (*grpc.ClientConn, error) {
+		return grpc.Dial("example.com", grpc.WithInsecure())
+	}, 1, 1, 0, time.Minute)
+	if err != nil {
+		t.Errorf("The pool returned an error: %s", err.Error())
+	}
+
+	c, err = p.Get(context.Background())
+	if err != nil {
+		t.Errorf("Get returned an error: %s", err.Error())
+	}
+
+	// The max life of the connection was very low (1ns), so when we close
+	// the connection it should get marked as unhealthy
+	if err := c.Close(); err != nil {
+		t.Errorf("Close returned an error: %s", err.Error())
+	}
+	if c.unhealthy {
+		t.Errorf("the connection shouldn't have been marked as unhealthy")
+	}
 }