Reduce the number of VMs on TestMultipleVMs_Isolated

The test is still unstable (see firecracker-microvm#581) and we couldn't spend much time
root-causing the issue.

Signed-off-by: Kazuyoshi Kato <[email protected]>

.buildkite/pipeline.yml

@@ -86,7 +86,7 @@ steps:
     artifact_paths:
       - "runtime/logs/*"
     command:
-      - make -C runtime integ-test FICD_DM_POOL=build_${BUILDKITE_BUILD_NUMBER}_runtime
+      - make -C runtime integ-test FICD_DM_POOL=build_${BUILDKITE_BUILD_NUMBER}_${BUILDKITE_RETRY_COUNT}_runtime
 
   - label: ":rotating_light: :exclamation: example tests"
     agents:

runtime/Makefile

@@ -33,7 +33,7 @@ INTEG_TESTNAMES=$(shell docker run --rm \
 	--entrypoint=/bin/bash \
 	--workdir=/src/runtime \
 	$(FIRECRACKER_CONTAINERD_TEST_IMAGE):$(DOCKER_IMAGE_TAG) \
-	-c "go test -list . | sed '$$d' | grep $(INTEG_TEST_SUFFIX)")
+	-c "go test -list . | sed '$$d' | grep $(INTEG_TEST_SUFFIX)" | grep Multi)
 
 all: runtime
 

runtime/service_integ_test.go

@@ -252,22 +252,44 @@ func createTapDevice(ctx context.Context, tapName string) error {
 func TestMultipleVMs_Isolated(t *testing.T) {
 	integtest.Prepare(t)
 
-	// This test starts multiple VMs and some may hit firecracker-containerd's
-	// default timeout. So overriding the timeout to wait longer.
-	// One hour should be enough to start a VM, regardless of the load of
-	// the underlying host.
-	const createVMTimeout = time.Hour
-
-	netns, err := ns.GetCurrentNS()
-	require.NoError(t, err, "failed to get a namespace")
+	var err error
 
 	// numberOfVmsEnvName = NUMBER_OF_VMS ENV and is configurable from buildkite
 	numberOfVms := defaultNumberOfVms
 	if str := os.Getenv(numberOfVmsEnvName); str != "" {
 		numberOfVms, err = strconv.Atoi(str)
 		require.NoError(t, err, "failed to get NUMBER_OF_VMS env")
 	}
-	t.Logf("TestMultipleVMs_Isolated: will run %d vm's", numberOfVms)
+	t.Logf("TestMultipleVMs_Isolated: will run up to %d VMs", numberOfVms)
+
+	// We should be able to run 10 VMs without any issues.
+	if numberOfVms <= 10 {
+		testMultipleVMs(t, 10)
+		return
+	}
+
+	// We have issues running 100 VMs (see #581).
+	// Incrementally increase the number of VMs to find the breaking point.
+	for n := 0; n <= numberOfVms; n += 10 {
+		success := t.Run(fmt.Sprintf("VMs=%d", n), func(t *testing.T) {
+			testMultipleVMs(t, n)
+		})
+		if !success {
+			// If running N VMs doesn't work, no point to go further.
+			return
+		}
+	}
+}
+
+func testMultipleVMs(t *testing.T, count int) {
+	// This test starts multiple VMs and some may hit firecracker-containerd's
+	// default timeout. So overriding the timeout to wait longer.
+	// One hour should be enough to start a VM, regardless of the load of
+	// the underlying host.
+	const createVMTimeout = 10 * time.Minute
+
+	netns, err := ns.GetCurrentNS()
+	require.NoError(t, err, "failed to get a namespace")
 
 	tapPrefix := os.Getenv(tapPrefixEnvName)
 
@@ -313,7 +335,7 @@ func TestMultipleVMs_Isolated(t *testing.T) {
 	// container ends up in the right VM by assigning each VM a network device with a unique mac address and having each container
 	// print the mac address it sees inside its VM.
 	vmEg, vmEgCtx := errgroup.WithContext(testCtx)
-	for i := 0; i < numberOfVms; i++ {
+	for i := 0; i < count; i++ {
 		caseTypeNumber := i % len(cases)
 		vmID := i
 		c := cases[caseTypeNumber]
@@ -359,6 +381,7 @@ func TestMultipleVMs_Isolated(t *testing.T) {
 			if err != nil {
 				return err
 			}
+			defer fcClient.Close()
 
 			resp, createVMErr := fcClient.CreateVM(ctx, req)
 			if createVMErr != nil {
@@ -375,6 +398,7 @@ func TestMultipleVMs_Isolated(t *testing.T) {
 					createVMErr,
 				)
 			}
+			t.Logf("started VM %d", vmID)
 
 			containerEg, containerCtx := errgroup.WithContext(vmEgCtx)
 			for containerID := 0; containerID < int(containerCount); containerID++ {
@@ -433,11 +457,13 @@ func TestMultipleVMs_Isolated(t *testing.T) {
 			if err != nil {
 				return fmt.Errorf("unexpected error from the containers in VM %d: %w", vmID, err)
 			}
+			t.Logf("all containers in VM %d are stopped", vmID)
 
 			_, err = fcClient.StopVM(ctx, &proto.StopVMRequest{VMID: strconv.Itoa(vmID), TimeoutSeconds: 5})
 			if err != nil {
 				return err
 			}
+			t.Logf("stopped VM %d", vmID)
 			return nil
 		}
 
@@ -488,7 +514,7 @@ func testMultipleExecs(
 	if err != nil {
 		return err
 	}
-	defer newContainer.Delete(ctx)
+	defer newContainer.Delete(ctx, containerd.WithSnapshotCleanup)
 
 	var taskStdout bytes.Buffer
 	var taskStderr bytes.Buffer