Double-check while locking in DynamicRESTMapper

This ensures that the DynamicRESTMapper will double-check after
acquiring a lock that it still needs to refresh.  This avoids the
situation where two requests come in at the same time, both require the
same missing resource, and both end up issuing (potentially expensive)
discovery requests, even though simply issuing one would have sufficed.

This also adds tests to ensure proper behavior, and limits discovery
re-requests to 10 per second.

Author: DirectXMan12

pkg/client/apiutil/apiutil_suite_test.go

@@ -0,0 +1,45 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package apiutil_test
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	"k8s.io/client-go/rest"
+	"sigs.k8s.io/controller-runtime/pkg/envtest"
+
+	logf "sigs.k8s.io/controller-runtime/pkg/log"
+	"sigs.k8s.io/controller-runtime/pkg/log/zap"
+)
+
+func TestSource(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecsWithDefaultAndCustomReporters(t, "API Utilities Test Suite", []Reporter{envtest.NewlineReporter{}})
+}
+
+var cfg *rest.Config
+
+var _ = BeforeSuite(func(done Done) {
+	logf.SetLogger(zap.LoggerTo(GinkgoWriter, true))
+
+	// for things that technically need a rest.Config for defaulting, but don't actually use them
+	cfg = &rest.Config{}
+
+	close(done)
+}, 60)