Add feature to mount tmpfs volumes

charts/k8s-service/templates/_deployment_spec.tpl

@@ -69,6 +69,9 @@ We need this because certain sections are omitted if there are no volumes or env
 {{- if gt (len .Values.persistentVolumes) 0 -}}
   {{- $_ := set $hasInjectionTypes "hasVolume" true -}}
 {{- end -}}
+{{- if gt (len .Values.scratchPaths) 0 -}}
+  {{- $_ := set $hasInjectionTypes "hasVolume" true -}}
+{{- end -}}
 apiVersion: apps/v1
 kind: Deployment
 metadata:
@@ -288,6 +291,10 @@ spec:
             - name: {{ $name }}
               mountPath: {{ quote $value.mountPath }}
           {{- end }}
+          {{- range $name, $value := .Values.scratchPaths }}
+            - name: {{ $name }}
+              mountPath: {{ quote $value }}
+          {{- end }}
           {{- /* END VOLUME MOUNT LOGIC */ -}}
 
         {{- range $key, $value := .Values.sideCarContainers }}
@@ -357,6 +364,11 @@ spec:
           persistentVolumeClaim:
             claimName: {{ $value.claimName }}
     {{- end }}
+    {{- range $name, $value := .Values.scratchPaths }}
+        - name: {{ $name }}
+          emptyDir:
+            medium: "Memory"
+    {{- end }}
     {{- /* END VOLUME LOGIC */ -}}
 
     {{- with .Values.nodeSelector }}

charts/k8s-service/values.yaml

@@ -404,6 +404,15 @@ configMaps: {}
 #
 persistentVolumes: {}
 
+# scratchPaths is a map of key value pairs that specifies which paths in the container should be setup as scratch space.
+# Under the hood each entry in the map is converted to a tmpfs volume with the name set to the key and mounted into the
+# container on the path provided as the value.
+#
+# EXAMPLE:
+# scratchPaths:
+#   example: /mnt/scratch
+scratchPaths: {}
+
 # secrets is a map that specifies the Secret resources that should be exposed to the main application container. Each entry in
 # the map represents a Secret resource. The key refers to the name of the Secret that should be exposed, with the value
 # specifying how to expose the Secret. The value is also a map and has the following attributes:

test/k8s_service_config_injection_example_test.go

@@ -59,7 +59,7 @@ func TestK8SServiceConfigInjectionBaseExample(t *testing.T) {
 	// Verify the app comes up cleanly and returns the expected text
 	expectedText := "Hello from backend"
 	validationFunction := sampleAppValidationFunctionGenerator(t, expectedText)
-	verifyPodsCreatedSuccessfully(t, kubectlOptions, "sample-sinatra-app", releaseName)
+	verifyPodsCreatedSuccessfully(t, kubectlOptions, "sample-sinatra-app", releaseName, NumPodsExpected)
 	verifyAllPodsAvailable(t, kubectlOptions, "sample-sinatra-app", releaseName, validationFunction)
 	verifyServiceAvailable(t, kubectlOptions, "sample-sinatra-app", releaseName, validationFunction)
 
@@ -119,7 +119,7 @@ func TestK8SServiceConfigInjectionConfigMapExample(t *testing.T) {
 	// Verify the app comes up cleanly and returns the expected text
 	expectedText := "Hello! I was configured using a ConfigMap!"
 	validationFunction := sampleAppValidationFunctionGenerator(t, expectedText)
-	verifyPodsCreatedSuccessfully(t, kubectlOptions, "sample-sinatra-app", releaseName)
+	verifyPodsCreatedSuccessfully(t, kubectlOptions, "sample-sinatra-app", releaseName, NumPodsExpected)
 	verifyAllPodsAvailable(t, kubectlOptions, "sample-sinatra-app", releaseName, validationFunction)
 	verifyServiceAvailable(t, kubectlOptions, "sample-sinatra-app", releaseName, validationFunction)
 }
@@ -189,7 +189,7 @@ func TestK8SServiceConfigInjectionSecretExample(t *testing.T) {
 	// Verify the app comes up cleanly and returns the expected text
 	expectedText := "Hello! I was configured using a Secret!"
 	validationFunction := sampleAppValidationFunctionGenerator(t, expectedText)
-	verifyPodsCreatedSuccessfully(t, kubectlOptions, "sample-sinatra-app", releaseName)
+	verifyPodsCreatedSuccessfully(t, kubectlOptions, "sample-sinatra-app", releaseName, NumPodsExpected)
 	verifyAllPodsAvailable(t, kubectlOptions, "sample-sinatra-app", releaseName, validationFunction)
 	verifyServiceAvailable(t, kubectlOptions, "sample-sinatra-app", releaseName, validationFunction)
 }

test/k8s_service_example_test_helpers.go

@@ -39,13 +39,14 @@ func verifyPodsCreatedSuccessfully(
 	kubectlOptions *k8s.KubectlOptions,
 	appName string,
 	releaseName string,
+	numPods int,
 ) {
 	// Get the pods and wait until they are all ready
 	filters := metav1.ListOptions{
 		LabelSelector: fmt.Sprintf("app.kubernetes.io/name=%s,app.kubernetes.io/instance=%s", appName, releaseName),
 	}
 
-	k8s.WaitUntilNumPodsCreated(t, kubectlOptions, filters, NumPodsExpected, WaitTimerRetries, WaitTimerSleep)
+	k8s.WaitUntilNumPodsCreated(t, kubectlOptions, filters, numPods, WaitTimerRetries, WaitTimerSleep)
 	pods := k8s.ListPods(t, kubectlOptions, filters)
 
 	for _, pod := range pods {

test/k8s_service_nginx_example_test.go

@@ -12,7 +12,7 @@ import (
 	"testing"
 
 	"github.com/gruntwork-io/terratest/modules/helm"
-	"github.com/gruntwork-io/terratest/modules/http-helper"
+	http_helper "github.com/gruntwork-io/terratest/modules/http-helper"
 	"github.com/gruntwork-io/terratest/modules/k8s"
 	"github.com/gruntwork-io/terratest/modules/random"
 	"github.com/stretchr/testify/require"
@@ -67,7 +67,7 @@ func TestK8SServiceNginxExample(t *testing.T) {
 	defer helm.Delete(t, options, releaseName, true)
 	helm.Install(t, options, helmChartPath, releaseName)
 
-	verifyPodsCreatedSuccessfully(t, kubectlOptions, "nginx", releaseName)
+	verifyPodsCreatedSuccessfully(t, kubectlOptions, "nginx", releaseName, NumPodsExpected)
 	verifyAllPodsAvailable(t, kubectlOptions, "nginx", releaseName, nginxValidationFunction)
 	verifyServiceAvailable(t, kubectlOptions, "nginx", releaseName, nginxValidationFunction)
 
@@ -85,7 +85,7 @@ func TestK8SServiceNginxExample(t *testing.T) {
 	helm.Upgrade(t, options, helmChartPath, releaseName)
 
 	// We expect the service to still come up cleanly
-	verifyPodsCreatedSuccessfully(t, kubectlOptions, "nginx", releaseName)
+	verifyPodsCreatedSuccessfully(t, kubectlOptions, "nginx", releaseName, NumPodsExpected)
 	verifyAllPodsAvailable(t, kubectlOptions, "nginx", releaseName, nginxValidationFunction)
 	verifyServiceAvailable(t, kubectlOptions, "nginx", releaseName, nginxValidationFunction)
 

test/k8s_service_template_test.go

@@ -753,37 +753,3 @@ func TestK8SServicePodAddingAdditionalLabels(t *testing.T) {
 	assert.Equal(t, deployment.Spec.Template.Labels["first-label"], first_custom_pod_label_value)
 	assert.Equal(t, deployment.Spec.Template.Labels["second-label"], second_custom_pod_label_value)
 }
-
-func TestK8SServiceDeploymentAddingPersistentVolumes(t *testing.T) {
-	t.Parallel()
-
-	volName := "pv-1"
-	volClaim := "claim-1"
-	volMountPath := "/mnt/path/1"
-
-	deployment := renderK8SServiceDeploymentWithSetValues(
-		t,
-		map[string]string{
-			"persistentVolumes.pv-1.claimName": volClaim,
-			"persistentVolumes.pv-1.mountPath": volMountPath,
-		},
-	)
-
-	// Verify that there is only one container and that the environments section is populated.
-	renderedPodContainers := deployment.Spec.Template.Spec.Containers
-	require.Equal(t, len(renderedPodContainers), 1)
-
-	// Verify that a mount has been created for the PV
-	mounts := renderedPodContainers[0].VolumeMounts
-	assert.Equal(t, len(mounts), 1)
-	mount := mounts[0]
-	assert.Equal(t, volName, mount.Name)
-	assert.Equal(t, volMountPath, mount.MountPath)
-
-	// Verify that a volume has been declared for the PV
-	volumes := deployment.Spec.Template.Spec.Volumes
-	assert.Equal(t, len(volumes), 1)
-	volume := volumes[0]
-	assert.Equal(t, volName, volume.Name)
-	assert.Equal(t, volClaim, volume.PersistentVolumeClaim.ClaimName)
-}

test/k8s_service_volume_template_test.go

@@ -0,0 +1,83 @@
+// +build all tpl
+
+// NOTE: We use build flags to differentiate between template tests and integration tests so that you can conveniently
+// run just the template tests. See the test README for more information.
+
+package test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	corev1 "k8s.io/api/core/v1"
+)
+
+func TestK8SServiceDeploymentAddingScratchVolumes(t *testing.T) {
+	t.Parallel()
+
+	volName := "scratch"
+	volMountPath := "/mnt/scratch"
+
+	deployment := renderK8SServiceDeploymentWithSetValues(
+		t,
+		map[string]string{
+			fmt.Sprintf("scratchPaths.%s", volName): volMountPath,
+		},
+	)
+
+	// Verify that there is only one container
+	renderedPodContainers := deployment.Spec.Template.Spec.Containers
+	require.Equal(t, len(renderedPodContainers), 1)
+	podContainer := renderedPodContainers[0]
+
+	// Verify that a mount has been created for the scratch path
+	mounts := podContainer.VolumeMounts
+	assert.Equal(t, len(mounts), 1)
+	mount := mounts[0]
+	assert.Equal(t, volName, mount.Name)
+	assert.Equal(t, volMountPath, mount.MountPath)
+
+	// Verify that a volume has been declared for the scratch path and is using tmpfs
+	volumes := deployment.Spec.Template.Spec.Volumes
+	assert.Equal(t, len(volumes), 1)
+	volume := volumes[0]
+	assert.Equal(t, volName, volume.Name)
+	assert.Equal(t, corev1.StorageMediumMemory, volume.EmptyDir.Medium)
+
+}
+
+func TestK8SServiceDeploymentAddingPersistentVolumes(t *testing.T) {
+	t.Parallel()
+
+	volName := "pv-1"
+	volClaim := "claim-1"
+	volMountPath := "/mnt/path/1"
+
+	deployment := renderK8SServiceDeploymentWithSetValues(
+		t,
+		map[string]string{
+			"persistentVolumes.pv-1.claimName": volClaim,
+			"persistentVolumes.pv-1.mountPath": volMountPath,
+		},
+	)
+
+	// Verify that there is only one container
+	renderedPodContainers := deployment.Spec.Template.Spec.Containers
+	require.Equal(t, len(renderedPodContainers), 1)
+
+	// Verify that a mount has been created for the PV
+	mounts := renderedPodContainers[0].VolumeMounts
+	assert.Equal(t, len(mounts), 1)
+	mount := mounts[0]
+	assert.Equal(t, volName, mount.Name)
+	assert.Equal(t, volMountPath, mount.MountPath)
+
+	// Verify that a volume has been declared for the PV
+	volumes := deployment.Spec.Template.Spec.Volumes
+	assert.Equal(t, len(volumes), 1)
+	volume := volumes[0]
+	assert.Equal(t, volName, volume.Name)
+	assert.Equal(t, volClaim, volume.PersistentVolumeClaim.ClaimName)
+}

test/k8s_service_volume_test.go

@@ -0,0 +1,64 @@
+// +build all integration
+
+// NOTE: We use build flags to differentiate between template tests and integration tests so that you can conveniently
+// run just the template tests. See the test README for more information.
+
+package test
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/gruntwork-io/terratest/modules/helm"
+	"github.com/gruntwork-io/terratest/modules/k8s"
+	"github.com/gruntwork-io/terratest/modules/random"
+	"github.com/stretchr/testify/require"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func TestK8SServiceScratchSpaceIsTmpfs(t *testing.T) {
+	t.Parallel()
+
+	helmChartPath, err := filepath.Abs(filepath.Join("..", "charts", "k8s-service"))
+	require.NoError(t, err)
+
+	// Create a test namespace to deploy resources into, to avoid colliding with other tests
+	kubectlOptions := k8s.NewKubectlOptions("", "", "")
+	uniqueID := random.UniqueId()
+	testNamespace := fmt.Sprintf("k8s-service-scratch-%s", strings.ToLower(uniqueID))
+	k8s.CreateNamespace(t, kubectlOptions, testNamespace)
+	defer k8s.DeleteNamespace(t, kubectlOptions, testNamespace)
+	kubectlOptions.Namespace = testNamespace
+
+	// Construct the values to run a pod with scratch space
+	releaseName := fmt.Sprintf("k8s-service-scratch-%s", strings.ToLower(uniqueID))
+	appName := "scratch-tester"
+	options := &helm.Options{
+		KubectlOptions: kubectlOptions,
+		SetValues: map[string]string{
+			"applicationName":           appName,
+			"containerImage.repository": "alpine",
+			"containerImage.tag":        "3.13",
+			"containerImage.pullPolicy": "IfNotPresent",
+			"containerCommand[0]":       "sh",
+			"containerCommand[1]":       "-c",
+			"containerCommand[2]":       "mount && sleep 9999999",
+			"scratchPaths.scratch-mnt":  "/mnt/scratch",
+		},
+	}
+	defer helm.Delete(t, options, releaseName, true)
+	helm.Install(t, options, helmChartPath, releaseName)
+
+	// Make sure all the pods are deployed and available
+	verifyPodsCreatedSuccessfully(t, kubectlOptions, appName, releaseName, 1)
+
+	// Get the logs from the pod to verify /mnt/scratch is mounted as tmpfs.
+	pods := k8s.ListPods(t, kubectlOptions, metav1.ListOptions{})
+	require.Equal(t, 1, len(pods))
+	pod := pods[0]
+	logs, err := k8s.RunKubectlAndGetOutputE(t, kubectlOptions, "logs", pod.Name)
+	require.NoError(t, err)
+	require.Contains(t, logs, "tmpfs on /mnt/scratch type tmpfs (rw,relatime)")
+}