Added HostErrorsCache for tracking failed hosts

v2/pkg/protocols/common/hosterrorscache/hosterrorscache_test.go

@@ -0,0 +1,30 @@
+package hosterrorscache
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestCacheCheckMarkFailed(t *testing.T) {
+	cache := New(3, DefaultMaxHostsCount)
+
+	cache.MarkFailed("http://example.com:80")
+	if value, err := cache.failedTargets.Get("http://example.com:80"); err == nil && value != nil {
+		require.Equal(t, 1, value, "could not get correct markfailed")
+	}
+	cache.MarkFailed("example.com:80")
+	if value, err := cache.failedTargets.Get("example.com:80"); err == nil && value != nil {
+		require.Equal(t, 2, value, "could not get correct markfailed")
+	}
+	cache.MarkFailed("example.com")
+	if value, err := cache.failedTargets.Get("example.com"); err == nil && value != nil {
+		require.Equal(t, 1, value, "could not get correct markfailed")
+	}
+	for i := 0; i < 3; i++ {
+		cache.MarkFailed("test")
+	}
+
+	value := cache.Check("test")
+	require.Equal(t, true, value, "could not get checked value")
+}