e2e/storage: test usage of volume in multiple pods at once

This is a special case that both kubelet and the volume driver should
support, because users might expect it. One Kubernetes mechanism to
deploy pods like this is via pod affinity.

However, strictly speaking the CSI spec does not allow this usage
mode (see container-storage-interface/spec#150) and
there is an on-going debate to enable it (see
container-storage-interface/spec#178). Therefore
this test gets skipped unless explicitly enabled for a driver.

CSI drivers which create a block device for a remote volume in
NodePublishVolume fail this test. They have to make the volume
available in NodeStageVolume and then in NodePublishVolume merely do a
bind mount (as for example in
https://github.com/kubernetes-sigs/gcp-compute-persistent-disk-csi-driver/blob/master/pkg/gce-pd-csi-driver/node.go#L150).

Author: pohly

test/e2e/storage/drivers/csi.go

@@ -71,6 +71,7 @@ func initHostPathCSIDriver(name string, config testsuites.TestConfig, manifests
 			),
 			Capabilities: map[testsuites.Capability]bool{
 				testsuites.CapPersistence: true,
+				testsuites.CapMultiPODs:   true,
 			},
 
 			Config: config,

test/e2e/storage/testsuites/provisioning.go

@@ -18,6 +18,7 @@ package testsuites
 
 import (
 	"fmt"
+	"sync"
 	"time"
 
 	. "github.com/onsi/ginkgo"
@@ -218,6 +219,50 @@ func testProvisioning(input *provisioningTestInput) {
 		input.pvc.Spec.VolumeMode = &block
 		TestDynamicProvisioning(input.testCase, input.cs, input.pvc, input.sc)
 	})
+
+	It("should allow concurrent writes on the same node", func() {
+		if !input.dInfo.Capabilities[CapMultiPODs] {
+			framework.Skipf("Driver %q does not support multiple concurrent pods - skipping", input.dInfo.Name)
+		}
+		input.testCase.PvCheck = func(claim *v1.PersistentVolumeClaim, volume *v1.PersistentVolume) {
+			// We start two pods concurrently on the same node,
+			// using the same PVC. Both wait for other to create a
+			// file before returning. The pods are forced onto the
+			// same node via pod affinity.
+			wg := sync.WaitGroup{}
+			wg.Add(2)
+			firstPodName := "pvc-tester-first"
+			secondPodName := "pvc-tester-second"
+			run := func(podName, command string) {
+				defer GinkgoRecover()
+				defer wg.Done()
+				node := NodeSelection{
+					Name: input.nodeName,
+				}
+				if podName == secondPodName {
+					node.Affinity = &v1.Affinity{
+						PodAffinity: &v1.PodAffinity{
+							RequiredDuringSchedulingIgnoredDuringExecution: []v1.PodAffinityTerm{
+								{LabelSelector: &metav1.LabelSelector{
+									MatchLabels: map[string]string{
+										// Set by RunInPodWithVolume.
+										"app": firstPodName,
+									},
+								},
+									TopologyKey: "kubernetes.io/hostname",
+								},
+							},
+						},
+					}
+				}
+				RunInPodWithVolume(input.cs, claim.Namespace, claim.Name, podName, command, node)
+			}
+			go run(firstPodName, "touch /mnt/test/first && while ! [ -f /mnt/test/second ]; do sleep 1; done")
+			go run(secondPodName, "touch /mnt/test/second && while ! [ -f /mnt/test/first ]; do sleep 1; done")
+			wg.Wait()
+		}
+		TestDynamicProvisioning(input.testCase, input.cs, input.pvc, input.sc)
+	})
 }
 
 // TestDynamicProvisioning tests dynamic provisioning with specified StorageClassTest and storageClass
@@ -530,6 +575,9 @@ func StartInPodWithVolume(c clientset.Interface, ns, claimName, podName, command
 		},
 		ObjectMeta: metav1.ObjectMeta{
 			GenerateName: podName + "-",
+			Labels: map[string]string{
+				"app": podName,
+			},
 		},
 		Spec: v1.PodSpec{
 			NodeName:     node.Name,

test/e2e/storage/testsuites/testdriver.go

@@ -86,6 +86,13 @@ const (
 	CapBlock       Capability = "block"       // raw block mode
 	CapFsGroup     Capability = "fsGroup"     // volume ownership via fsGroup
 	CapExec        Capability = "exec"        // exec a file in the volume
+
+	// multiple pods on a node can use the same volume concurrently;
+	// for CSI, see:
+	// - https://github.com/container-storage-interface/spec/pull/150
+	// - https://github.com/container-storage-interface/spec/issues/178
+	// - NodeStageVolume in the spec
+	CapMultiPODs Capability = "multipods"
 )
 
 // DriverInfo represents a combination of parameters to be used in implementation of TestDriver